diff --git a/arduino/builder/cpp.go b/arduino/builder/cpp/cpp.go
similarity index 62%
rename from arduino/builder/cpp.go
rename to arduino/builder/cpp/cpp.go
index 87610e7ed18..71c2b696702 100644
--- a/arduino/builder/cpp.go
+++ b/arduino/builder/cpp/cpp.go
@@ -13,29 +13,63 @@
 // Arduino software without disclosing the source code of your own applications.
 // To purchase a commercial license, send an email to license@arduino.cc.
 
-package builder
+package cpp
 
 import (
+	"strconv"
 	"strings"
 	"unicode/utf8"
+
+	"github.com/arduino/go-paths-helper"
 )
 
-// QuoteCppString returns the given string as a quoted string for use with the C
+// QuoteString returns the given string as a quoted string for use with the C
 // preprocessor. This adds double quotes around it and escapes any
 // double quotes and backslashes in the string.
-func QuoteCppString(str string) string {
+func QuoteString(str string) string {
 	str = strings.Replace(str, "\\", "\\\\", -1)
 	str = strings.Replace(str, "\"", "\\\"", -1)
 	return "\"" + str + "\""
 }
 
-// ParseCppString parse a C-preprocessor string as emitted by the preprocessor. This
+// ParseLineMarker parses the given line as a gcc line marker and returns the contained
+// filename.
+func ParseLineMarker(line string) *paths.Path {
+	// A line marker contains the line number and filename and looks like:
+	// # 123 /path/to/file.cpp
+	// It can be followed by zero or more flag number that indicate the
+	// preprocessor state and can be ignored.
+	// For exact details on this format, see:
+	// https://github.com/gcc-mirror/gcc/blob/edd716b6b1caa1a5cb320a8cd7f626f30198e098/gcc/c-family/c-ppoutput.c#L413-L415
+
+	split := strings.SplitN(line, " ", 3)
+	if len(split) < 3 || len(split[0]) == 0 || split[0][0] != '#' {
+		return nil
+	}
+
+	_, err := strconv.Atoi(split[1])
+	if err != nil {
+		return nil
+	}
+
+	// If we get here, we found a # followed by a line number, so
+	// assume this is a line marker and see if the rest of the line
+	// starts with a string containing the filename
+	str, rest, ok := ParseString(split[2])
+
+	if ok && (rest == "" || rest[0] == ' ') {
+		return paths.New(str)
+	}
+	return nil
+}
+
+// ParseString parse a string as emitted by the preprocessor. This
 // is a string contained in double quotes, with any backslashes or
 // quotes escaped with a backslash. If a valid string was present at the
 // start of the given line, returns the unquoted string contents, the
 // remainder of the line (everything after the closing "), and true.
 // Otherwise, returns the empty string, the entire line and false.
-func ParseCppString(line string) (string, string, bool) {
+func ParseString(line string) (string, string, bool) {
 	// For details about how these strings are output by gcc, see:
 	// https://github.com/gcc-mirror/gcc/blob/a588355ab948cf551bc9d2b89f18e5ae5140f52c/libcpp/macro.c#L491-L511
 	// Note that the documentation suggests all non-printable
diff --git a/arduino/builder/cpp/cpp_test.go b/arduino/builder/cpp/cpp_test.go
new file mode 100644
index 00000000000..b6ae543f558
--- /dev/null
+++ b/arduino/builder/cpp/cpp_test.go
@@ -0,0 +1,74 @@
+// This file is part of arduino-cli.
+//
+// Copyright 2023 ARDUINO SA (http://www.arduino.cc/)
+//
+// This software is released under the GNU General Public License version 3,
+// which covers the main part of arduino-cli.
+// The terms of this license can be found at:
+// https://www.gnu.org/licenses/gpl-3.0.en.html
+//
+// You can be released from the requirements of the above licenses by purchasing
+// a commercial license. Buying such a license is mandatory if you want to
+// modify or otherwise use the software for commercial activities involving the
+// Arduino software without disclosing the source code of your own applications.
+// To purchase a commercial license, send an email to license@arduino.cc.
+
+package cpp_test
+
+import (
+	"testing"
+
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
+	"github.com/stretchr/testify/require"
+)
+
+func TestParseString(t *testing.T) {
+	_, _, ok := cpp.ParseString(`foo`)
+	require.Equal(t, false, ok)
+
+	_, _, ok = cpp.ParseString(`"foo`)
+	require.Equal(t, false, ok)
+
+	str, rest, ok := cpp.ParseString(`"foo"`)
+	require.Equal(t, true, ok)
+	require.Equal(t, `foo`, str)
+	require.Equal(t, ``, rest)
+
+	str, rest, ok = cpp.ParseString(`"foo\\bar"`)
+	require.Equal(t, true, ok)
+	require.Equal(t, `foo\bar`, str)
+	require.Equal(t, ``, rest)
+
+	str, rest, ok = cpp.ParseString(`"foo \"is\" quoted and \\\\bar\"\" escaped\\" and "then" some`)
+	require.Equal(t, true, ok)
+	require.Equal(t, `foo "is" quoted and \\bar"" escaped\`, str)
+	require.Equal(t, ` and "then" some`, rest)
+
+	str, rest, ok = cpp.ParseString(`" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_abcdefghijklmnopqrstuvwxyz{|}~"`)
+	require.Equal(t, true, ok)
+	require.Equal(t, ` !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_abcdefghijklmnopqrstuvwxyz{|}~`, str)
+	require.Equal(t, ``, rest)
+
+	str, rest, ok = cpp.ParseString(`"/home/ççç/"`)
+	require.Equal(t, true, ok)
+	require.Equal(t, `/home/ççç/`, str)
+	require.Equal(t, ``, rest)
+
+	str, rest, ok = cpp.ParseString(`"/home/ççç/ /$sdsdd\\"`)
+	require.Equal(t, true, ok)
+	require.Equal(t, `/home/ççç/ /$sdsdd\`, str)
+	require.Equal(t, ``, rest)
+}
+
+func TestQuoteString(t *testing.T) {
+	cases := map[string]string{
+		`foo`:                                  `"foo"`,
+		`foo\bar`:                              `"foo\\bar"`,
+		`foo "is" quoted and \\bar"" escaped\`: `"foo \"is\" quoted and \\\\bar\"\" escaped\\"`,
+		// ASCII 0x20 - 0x7e, excluding `
+		` !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_abcdefghijklmnopqrstuvwxyz{|}~`: `" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_abcdefghijklmnopqrstuvwxyz{|}~"`,
+	}
+	for input, expected := range cases {
+		require.Equal(t, expected, cpp.QuoteString(input))
+	}
+}
diff --git a/arduino/builder/cpp_test.go b/arduino/builder/cpp_test.go
deleted file mode 100644
index 84de5f0b254..00000000000
--- a/arduino/builder/cpp_test.go
+++ /dev/null
@@ -1,46 +0,0 @@
-package builder_test
-
-import (
-	"testing"
-
-	"github.com/arduino/arduino-cli/arduino/builder"
-	"github.com/stretchr/testify/require"
-)
-
-func TestParseCppString(t *testing.T) {
-	_, _, ok := builder.ParseCppString(`foo`)
-	require.Equal(t, false, ok)
-
-	_, _, ok = builder.ParseCppString(`"foo`)
-	require.Equal(t, false, ok)
-
-	str, rest, ok := builder.ParseCppString(`"foo"`)
-	require.Equal(t, true, ok)
-	require.Equal(t, `foo`, str)
-	require.Equal(t, ``, rest)
-
-	str, rest, ok = builder.ParseCppString(`"foo\\bar"`)
-	require.Equal(t, true, ok)
-	require.Equal(t, `foo\bar`, str)
-	require.Equal(t, ``, rest)
-
-	str, rest, ok = builder.ParseCppString(`"foo \"is\" quoted and \\\\bar\"\" escaped\\" and "then" some`)
-	require.Equal(t, true, ok)
-	require.Equal(t, `foo "is" quoted and \\bar"" escaped\`, str)
-	require.Equal(t, ` and "then" some`, rest)
-
-	str, rest, ok = builder.ParseCppString(`" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_abcdefghijklmnopqrstuvwxyz{|}~"`)
-	require.Equal(t, true, ok)
-	require.Equal(t, ` !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_abcdefghijklmnopqrstuvwxyz{|}~`, str)
-	require.Equal(t, ``, rest)
-
-	str, rest, ok = builder.ParseCppString(`"/home/ççç/"`)
-	require.Equal(t, true, ok)
-	require.Equal(t, `/home/ççç/`, str)
-	require.Equal(t, ``, rest)
-
-	str, rest, ok = builder.ParseCppString(`"/home/ççç/ /$sdsdd\\"`)
-	require.Equal(t, true, ok)
-	require.Equal(t, `/home/ççç/ /$sdsdd\`, str)
-	require.Equal(t, ``, rest)
-}
diff --git a/arduino/builder/preprocessor/ctags.go b/arduino/builder/preprocessor/ctags.go
index f079f54abf2..bf5f25b4ca2 100644
--- a/arduino/builder/preprocessor/ctags.go
+++ b/arduino/builder/preprocessor/ctags.go
@@ -16,10 +16,17 @@
 package preprocessor
 
 import (
+	"bufio"
+	"bytes"
 	"context"
 	"fmt"
+	"io"
+	"strconv"
 	"strings"
 
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
+	"github.com/arduino/arduino-cli/arduino/builder/preprocessor/internal/ctags"
+	"github.com/arduino/arduino-cli/arduino/sketch"
 	"github.com/arduino/arduino-cli/executils"
 	"github.com/arduino/arduino-cli/i18n"
 	"github.com/arduino/go-paths-helper"
@@ -29,6 +36,145 @@ import (
 
 var tr = i18n.Tr
 
+// DebugPreprocessor when set to true the CTags preprocessor will output debugging info to stdout
+// this is useful for unit-testing to provide more infos
+var DebugPreprocessor bool
+
+// PreprocessSketchWithCtags performs preprocessing of the arduino sketch using CTags.
+func PreprocessSketchWithCtags(sketch *sketch.Sketch, buildPath *paths.Path, includes paths.PathList, lineOffset int, buildProperties *properties.Map, onlyUpdateCompilationDatabase bool) ([]byte, []byte, error) {
+	// Create a temporary working directory
+	tmpDir, err := paths.MkTempDir("", "")
+	if err != nil {
+		return nil, nil, err
+	}
+	defer tmpDir.RemoveAll()
+	ctagsTarget := tmpDir.Join("sketch_merged.cpp")
+
+	normalOutput := &bytes.Buffer{}
+	verboseOutput := &bytes.Buffer{}
+
+	// Run GCC preprocessor
+	sourceFile := buildPath.Join("sketch", sketch.MainFile.Base()+".cpp")
+	gccStdout, gccStderr, err := GCC(sourceFile, ctagsTarget, includes, buildProperties)
+	verboseOutput.Write(gccStdout)
+	verboseOutput.Write(gccStderr)
+	normalOutput.Write(gccStderr)
+	if err != nil {
+		if !onlyUpdateCompilationDatabase {
+			return normalOutput.Bytes(), verboseOutput.Bytes(), errors.WithStack(err)
+		}
+
+		// Do not bail out if we are generating the compile commands database
+		normalOutput.WriteString(fmt.Sprintf("%s: %s",
+			tr("An error occurred adding prototypes"),
+			tr("the compilation database may be incomplete or inaccurate")))
+		if err := sourceFile.CopyTo(ctagsTarget); err != nil {
+			return normalOutput.Bytes(), verboseOutput.Bytes(), errors.WithStack(err)
+		}
+	}
+
+	if src, err := ctagsTarget.ReadFile(); err == nil {
+		filteredSource := filterSketchSource(sketch, bytes.NewReader(src), false)
+		if err := ctagsTarget.WriteFile([]byte(filteredSource)); err != nil {
+			return normalOutput.Bytes(), verboseOutput.Bytes(), err
+		}
+	} else {
+		return normalOutput.Bytes(), verboseOutput.Bytes(), err
+	}
+
+	// Run CTags on gcc-preprocessed source
+	ctagsOutput, ctagsStdErr, err := RunCTags(ctagsTarget, buildProperties)
+	verboseOutput.Write(ctagsStdErr)
+	if err != nil {
+		return normalOutput.Bytes(), verboseOutput.Bytes(), err
+	}
+
+	// Parse CTags output
+	parser := &ctags.Parser{}
+	prototypes, firstFunctionLine := parser.Parse(ctagsOutput, sketch.MainFile)
+	if firstFunctionLine == -1 {
+		firstFunctionLine = 0
+	}
+
+	// Add prototypes to the original sketch source
+	var source string
+	if sourceData, err := sourceFile.ReadFile(); err == nil {
+		source = string(sourceData)
+	} else {
+		return normalOutput.Bytes(), verboseOutput.Bytes(), err
+	}
+	source = strings.Replace(source, "\r\n", "\n", -1)
+	source = strings.Replace(source, "\r", "\n", -1)
+	sourceRows := strings.Split(source, "\n")
+	if isFirstFunctionOutsideOfSource(firstFunctionLine, sourceRows) {
+		return normalOutput.Bytes(), verboseOutput.Bytes(), nil
+	}
+
+	insertionLine := firstFunctionLine + lineOffset - 1
+	firstFunctionChar := len(strings.Join(sourceRows[:insertionLine], "\n")) + 1
+	prototypeSection := composePrototypeSection(firstFunctionLine, prototypes)
+	preprocessedSource := source[:firstFunctionChar] + prototypeSection + source[firstFunctionChar:]
+
+	if DebugPreprocessor {
+		fmt.Println("#PREPROCESSED SOURCE")
+		prototypesRows := strings.Split(prototypeSection, "\n")
+		prototypesRows = prototypesRows[:len(prototypesRows)-1]
+		for i := 0; i < len(sourceRows)+len(prototypesRows); i++ {
+			if i < insertionLine {
+				fmt.Printf("   |%s\n", sourceRows[i])
+			} else if i < insertionLine+len(prototypesRows) {
+				fmt.Printf("PRO|%s\n", prototypesRows[i-insertionLine])
+			} else {
+				fmt.Printf("   |%s\n", sourceRows[i-len(prototypesRows)])
+			}
+		}
+		fmt.Println("#END OF PREPROCESSED SOURCE")
+	}
+
+	// Write back arduino-preprocess output to the sourceFile
+	err = sourceFile.WriteFile([]byte(preprocessedSource))
+	return normalOutput.Bytes(), verboseOutput.Bytes(), err
+}
+
+func composePrototypeSection(line int, prototypes []*ctags.Prototype) string {
+	if len(prototypes) == 0 {
+		return ""
+	}
+
+	str := joinPrototypes(prototypes)
+	str += "\n#line "
+	str += strconv.Itoa(line)
+	str += " " + cpp.QuoteString(prototypes[0].File)
+	str += "\n"
+
+	return str
+}
+
+func joinPrototypes(prototypes []*ctags.Prototype) string {
+	prototypesSlice := []string{}
+	for _, proto := range prototypes {
+		if signatureContainsaDefaultArg(proto) {
+			continue
+		}
+		prototypesSlice = append(prototypesSlice, "#line "+strconv.Itoa(proto.Line)+" "+cpp.QuoteString(proto.File))
+		prototypeParts := []string{}
+		if proto.Modifiers != "" {
+			prototypeParts = append(prototypeParts, proto.Modifiers)
+		}
+		prototypeParts = append(prototypeParts, proto.Prototype)
+		prototypesSlice = append(prototypesSlice, strings.Join(prototypeParts, " "))
+	}
+	return strings.Join(prototypesSlice, "\n")
+}
+
+func signatureContainsaDefaultArg(proto *ctags.Prototype) bool {
+	return strings.Contains(proto.Prototype, "=")
+}
+
+func isFirstFunctionOutsideOfSource(firstFunctionLine int, sourceRows []string) bool {
+	return firstFunctionLine > len(sourceRows)-1
+}
+
 // RunCTags performs a run of ctags on the given source file. Returns the ctags output and the stderr contents.
 func RunCTags(sourceFile *paths.Path, buildProperties *properties.Map) ([]byte, []byte, error) {
 	ctagsBuildProperties := properties.NewMap()
@@ -60,3 +206,29 @@ func RunCTags(sourceFile *paths.Path, buildProperties *properties.Map) ([]byte,
 	stderr = append([]byte(args), stderr...)
 	return stdout, stderr, err
 }
+
+func filterSketchSource(sketch *sketch.Sketch, source io.Reader, removeLineMarkers bool) string {
+	fileNames := paths.NewPathList()
+	fileNames.Add(sketch.MainFile)
+	fileNames.AddAll(sketch.OtherSketchFiles)
+
+	inSketch := false
+	filtered := ""
+
+	scanner := bufio.NewScanner(source)
+	for scanner.Scan() {
+		line := scanner.Text()
+		if filename := cpp.ParseLineMarker(line); filename != nil {
+			inSketch = fileNames.Contains(filename)
+			if inSketch && removeLineMarkers {
+				continue
+			}
+		}
+
+		if inSketch {
+			filtered += line + "\n"
+		}
+	}
+
+	return filtered
+}
diff --git a/legacy/builder/ctags/ctags_has_issues.go b/arduino/builder/preprocessor/internal/ctags/ctags_has_issues.go
similarity index 89%
rename from legacy/builder/ctags/ctags_has_issues.go
rename to arduino/builder/preprocessor/internal/ctags/ctags_has_issues.go
index a61bf6c6c46..4d4d7d48f65 100644
--- a/legacy/builder/ctags/ctags_has_issues.go
+++ b/arduino/builder/preprocessor/internal/ctags/ctags_has_issues.go
@@ -23,17 +23,17 @@ import (
 	"golang.org/x/exp/slices"
 )
 
-func (p *CTagsParser) fixCLinkageTagsDeclarations() {
+func (p *Parser) fixCLinkageTagsDeclarations() {
 	linesMap := p.FindCLinkageLines(p.tags)
 	for i := range p.tags {
 		if slices.Contains(linesMap[p.tags[i].Filename], p.tags[i].Line) &&
-			!strings.Contains(p.tags[i].PrototypeModifiers, EXTERN) {
-			p.tags[i].PrototypeModifiers = p.tags[i].PrototypeModifiers + " " + EXTERN
+			!strings.Contains(p.tags[i].PrototypeModifiers, keywordExternC) {
+			p.tags[i].PrototypeModifiers = p.tags[i].PrototypeModifiers + " " + keywordExternC
 		}
 	}
 }
 
-func (p *CTagsParser) prototypeAndCodeDontMatch(tag *CTag) bool {
+func (p *Parser) prototypeAndCodeDontMatch(tag *Tag) bool {
 	if tag.SkipMe {
 		return true
 	}
@@ -98,7 +98,7 @@ func (p *CTagsParser) prototypeAndCodeDontMatch(tag *CTag) bool {
 	return ret == -1
 }
 
-func findTemplateMultiline(tag *CTag) string {
+func findTemplateMultiline(tag *Tag) string {
 	code, _ := getFunctionProtoUntilTemplateToken(tag, tag.Code)
 	return removeEverythingAfterClosingRoundBracket(code)
 }
@@ -108,7 +108,7 @@ func removeEverythingAfterClosingRoundBracket(s string) string {
 	return s[0 : n+1]
 }
 
-func getFunctionProtoUntilTemplateToken(tag *CTag, code string) (string, int) {
+func getFunctionProtoUntilTemplateToken(tag *Tag, code string) (string, int) {
 
 	/* FIXME I'm ugly */
 	line := 0
@@ -128,7 +128,7 @@ func getFunctionProtoUntilTemplateToken(tag *CTag, code string) (string, int) {
 			textBuffer = append(textBuffer, text)
 		}
 
-		for line > 0 && !strings.Contains(code, TEMPLATE) {
+		for line > 0 && !strings.Contains(code, keywordTemplate) {
 
 			line = line - 1
 			text := textBuffer[line]
@@ -141,7 +141,7 @@ func getFunctionProtoUntilTemplateToken(tag *CTag, code string) (string, int) {
 	return code, line
 }
 
-func getFunctionProtoWithNPreviousCharacters(tag *CTag, code string, n int) (string, int) {
+func getFunctionProtoWithNPreviousCharacters(tag *Tag, code string, n int) (string, int) {
 
 	/* FIXME I'm ugly */
 	expectedPrototypeLen := len(code) + n
@@ -204,10 +204,9 @@ func removeComments(text string, multilinecomment bool) (string, bool) {
 	return text, multilinecomment
 }
 
-/* This function scans the source files searching for "extern C" context
- * It save the line numbers in a map filename -> {lines...}
- */
-func (p *CTagsParser) FindCLinkageLines(tags []*CTag) map[string][]int {
+// FindCLinkageLines scans the source files searching for "extern C" context
+// It save the line numbers in a map filename -> {lines...}
+func (p *Parser) FindCLinkageLines(tags []*Tag) map[string][]int {
 
 	lines := make(map[string][]int)
 
@@ -245,7 +244,7 @@ func (p *CTagsParser) FindCLinkageLines(tags []*CTag) map[string][]int {
 			indentLevels := 0
 			line := 0
 
-			externCDecl := removeSpacesAndTabs(EXTERN)
+			externCDecl := removeSpacesAndTabs(keywordExternC)
 
 			for scanner.Scan() {
 				line++
diff --git a/legacy/builder/ctags/ctags_parser.go b/arduino/builder/preprocessor/internal/ctags/ctags_parser.go
similarity index 81%
rename from legacy/builder/ctags/ctags_parser.go
rename to arduino/builder/preprocessor/internal/ctags/ctags_parser.go
index 5836f7bf337..c2e6e99585f 100644
--- a/legacy/builder/ctags/ctags_parser.go
+++ b/arduino/builder/preprocessor/internal/ctags/ctags_parser.go
@@ -22,26 +22,28 @@ import (
 	"github.com/arduino/go-paths-helper"
 )
 
-const KIND_PROTOTYPE = "prototype"
-const KIND_FUNCTION = "function"
+const kindPrototype = "prototype"
+const kindFunction = "function"
 
 //const KIND_PROTOTYPE_MODIFIERS = "prototype_modifiers"
 
-const TEMPLATE = "template"
-const STATIC = "static"
-const EXTERN = "extern \"C\""
+const keywordTemplate = "template"
+const keywordStatic = "static"
+const keywordExternC = "extern \"C\""
 
-var KNOWN_TAG_KINDS = map[string]bool{
+var knownTagKinds = map[string]bool{
 	"prototype": true,
 	"function":  true,
 }
 
-type CTagsParser struct {
-	tags     []*CTag
+// Parser is a parser for ctags output
+type Parser struct {
+	tags     []*Tag
 	mainFile *paths.Path
 }
 
-type CTag struct {
+// Tag is a tag generated by ctags
+type Tag struct {
 	FunctionName string
 	Kind         string
 	Line         int
@@ -58,7 +60,8 @@ type CTag struct {
 	PrototypeModifiers string
 }
 
-func (p *CTagsParser) Parse(ctagsOutput []byte, mainFile *paths.Path) ([]*Prototype, int) {
+// Parse a ctags output and generates Prototypes
+func (p *Parser) Parse(ctagsOutput []byte, mainFile *paths.Path) ([]*Prototype, int) {
 	rows := strings.Split(string(ctagsOutput), "\n")
 	rows = removeEmpty(rows)
 
@@ -79,7 +82,7 @@ func (p *CTagsParser) Parse(ctagsOutput []byte, mainFile *paths.Path) ([]*Protot
 	return p.toPrototypes(), p.findLineWhereToInsertPrototypes()
 }
 
-func (p *CTagsParser) addPrototypes() {
+func (p *Parser) addPrototypes() {
 	for _, tag := range p.tags {
 		if !tag.SkipMe {
 			addPrototype(tag)
@@ -87,9 +90,9 @@ func (p *CTagsParser) addPrototypes() {
 	}
 }
 
-func addPrototype(tag *CTag) {
-	if strings.Index(tag.Prototype, TEMPLATE) == 0 {
-		if strings.Index(tag.Code, TEMPLATE) == 0 {
+func addPrototype(tag *Tag) {
+	if strings.Index(tag.Prototype, keywordTemplate) == 0 {
+		if strings.Index(tag.Code, keywordTemplate) == 0 {
 			code := tag.Code
 			if strings.Contains(code, "{") {
 				code = code[:strings.Index(code, "{")]
@@ -106,8 +109,8 @@ func addPrototype(tag *CTag) {
 	}
 
 	tag.PrototypeModifiers = ""
-	if strings.Contains(tag.Code, STATIC+" ") {
-		tag.PrototypeModifiers = tag.PrototypeModifiers + " " + STATIC
+	if strings.Contains(tag.Code, keywordStatic+" ") {
+		tag.PrototypeModifiers = tag.PrototypeModifiers + " " + keywordStatic
 	}
 
 	// Extern "C" modifier is now added in FixCLinkageTagsDeclarations
@@ -115,10 +118,10 @@ func addPrototype(tag *CTag) {
 	tag.PrototypeModifiers = strings.TrimSpace(tag.PrototypeModifiers)
 }
 
-func (p *CTagsParser) removeDefinedProtypes() {
+func (p *Parser) removeDefinedProtypes() {
 	definedPrototypes := make(map[string]bool)
 	for _, tag := range p.tags {
-		if tag.Kind == KIND_PROTOTYPE {
+		if tag.Kind == kindPrototype {
 			definedPrototypes[tag.Prototype] = true
 		}
 	}
@@ -133,7 +136,7 @@ func (p *CTagsParser) removeDefinedProtypes() {
 	}
 }
 
-func (p *CTagsParser) skipDuplicates() {
+func (p *Parser) skipDuplicates() {
 	definedPrototypes := make(map[string]bool)
 
 	for _, tag := range p.tags {
@@ -145,9 +148,9 @@ func (p *CTagsParser) skipDuplicates() {
 	}
 }
 
-type skipFuncType func(tag *CTag) bool
+type skipFuncType func(tag *Tag) bool
 
-func (p *CTagsParser) skipTagsWhere(skipFunc skipFuncType) {
+func (p *Parser) skipTagsWhere(skipFunc skipFuncType) {
 	for _, tag := range p.tags {
 		if !tag.SkipMe {
 			skip := skipFunc(tag)
@@ -169,11 +172,11 @@ func removeSpacesAndTabs(s string) string {
 	return s
 }
 
-func tagIsUnhandled(tag *CTag) bool {
+func tagIsUnhandled(tag *Tag) bool {
 	return !isHandled(tag)
 }
 
-func isHandled(tag *CTag) bool {
+func isHandled(tag *Tag) bool {
 	if tag.Class != "" {
 		return false
 	}
@@ -186,12 +189,12 @@ func isHandled(tag *CTag) bool {
 	return true
 }
 
-func tagIsUnknown(tag *CTag) bool {
-	return !KNOWN_TAG_KINDS[tag.Kind]
+func tagIsUnknown(tag *Tag) bool {
+	return !knownTagKinds[tag.Kind]
 }
 
-func parseTag(row string) *CTag {
-	tag := &CTag{}
+func parseTag(row string) *Tag {
+	tag := &Tag{}
 	parts := strings.Split(row, "\t")
 
 	tag.FunctionName = parts[0]
diff --git a/legacy/builder/ctags/ctags_parser_test.go b/arduino/builder/preprocessor/internal/ctags/ctags_parser_test.go
similarity index 98%
rename from legacy/builder/ctags/ctags_parser_test.go
rename to arduino/builder/preprocessor/internal/ctags/ctags_parser_test.go
index 97d5c85a4c9..7fc390cec67 100644
--- a/legacy/builder/ctags/ctags_parser_test.go
+++ b/arduino/builder/preprocessor/internal/ctags/ctags_parser_test.go
@@ -24,11 +24,11 @@ import (
 	"github.com/stretchr/testify/require"
 )
 
-func produceTags(t *testing.T, filename string) []*CTag {
-	bytes, err := os.ReadFile(filepath.Join("test_data", filename))
+func produceTags(t *testing.T, filename string) []*Tag {
+	bytes, err := os.ReadFile(filepath.Join("testdata", filename))
 	require.NoError(t, err)
 
-	parser := CTagsParser{}
+	parser := Parser{}
 	parser.Parse(bytes, paths.New("sketch.ino"))
 	return parser.tags
 }
diff --git a/legacy/builder/ctags/ctags_to_prototypes.go b/arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes.go
similarity index 80%
rename from legacy/builder/ctags/ctags_to_prototypes.go
rename to arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes.go
index 71cc072a6fa..95fc384f116 100644
--- a/legacy/builder/ctags/ctags_to_prototypes.go
+++ b/arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes.go
@@ -20,6 +20,7 @@ import (
 	"strings"
 )
 
+// Prototype is a C++ prototype generated from ctags output
 type Prototype struct {
 	FunctionName string
 	File         string
@@ -32,15 +33,14 @@ func (proto *Prototype) String() string {
 	return proto.Modifiers + " " + proto.Prototype + " @ " + strconv.Itoa(proto.Line)
 }
 
-func (p *CTagsParser) findLineWhereToInsertPrototypes() int {
+func (p *Parser) findLineWhereToInsertPrototypes() int {
 	firstFunctionLine := p.firstFunctionAtLine()
 	firstFunctionPointerAsArgument := p.firstFunctionPointerUsedAsArgument()
 	if firstFunctionLine != -1 && firstFunctionPointerAsArgument != -1 {
 		if firstFunctionLine < firstFunctionPointerAsArgument {
 			return firstFunctionLine
-		} else {
-			return firstFunctionPointerAsArgument
 		}
+		return firstFunctionPointerAsArgument
 	} else if firstFunctionLine != -1 {
 		return firstFunctionLine
 	} else if firstFunctionPointerAsArgument != -1 {
@@ -50,7 +50,7 @@ func (p *CTagsParser) findLineWhereToInsertPrototypes() int {
 	}
 }
 
-func (p *CTagsParser) firstFunctionPointerUsedAsArgument() int {
+func (p *Parser) firstFunctionPointerUsedAsArgument() int {
 	functionTags := p.collectFunctions()
 	for _, tag := range p.tags {
 		if functionNameUsedAsFunctionPointerIn(tag, functionTags) {
@@ -60,7 +60,7 @@ func (p *CTagsParser) firstFunctionPointerUsedAsArgument() int {
 	return -1
 }
 
-func functionNameUsedAsFunctionPointerIn(tag *CTag, functionTags []*CTag) bool {
+func functionNameUsedAsFunctionPointerIn(tag *Tag, functionTags []*Tag) bool {
 	for _, functionTag := range functionTags {
 		if tag.Line != functionTag.Line && strings.Contains(tag.Code, "&"+functionTag.FunctionName) {
 			return true
@@ -72,26 +72,26 @@ func functionNameUsedAsFunctionPointerIn(tag *CTag, functionTags []*CTag) bool {
 	return false
 }
 
-func (p *CTagsParser) collectFunctions() []*CTag {
-	functionTags := []*CTag{}
+func (p *Parser) collectFunctions() []*Tag {
+	functionTags := []*Tag{}
 	for _, tag := range p.tags {
-		if tag.Kind == KIND_FUNCTION && !tag.SkipMe {
+		if tag.Kind == kindFunction && !tag.SkipMe {
 			functionTags = append(functionTags, tag)
 		}
 	}
 	return functionTags
 }
 
-func (p *CTagsParser) firstFunctionAtLine() int {
+func (p *Parser) firstFunctionAtLine() int {
 	for _, tag := range p.tags {
-		if !tagIsUnknown(tag) && isHandled(tag) && tag.Kind == KIND_FUNCTION && tag.Filename == p.mainFile.String() {
+		if !tagIsUnknown(tag) && isHandled(tag) && tag.Kind == kindFunction && tag.Filename == p.mainFile.String() {
 			return tag.Line
 		}
 	}
 	return -1
 }
 
-func (p *CTagsParser) toPrototypes() []*Prototype {
+func (p *Parser) toPrototypes() []*Prototype {
 	prototypes := []*Prototype{}
 	for _, tag := range p.tags {
 		if strings.TrimSpace(tag.Prototype) == "" {
diff --git a/legacy/builder/ctags/ctags_to_prototypes_test.go b/arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes_test.go
similarity index 99%
rename from legacy/builder/ctags/ctags_to_prototypes_test.go
rename to arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes_test.go
index 98455c22202..bfec902d8d9 100644
--- a/legacy/builder/ctags/ctags_to_prototypes_test.go
+++ b/arduino/builder/preprocessor/internal/ctags/ctags_to_prototypes_test.go
@@ -25,10 +25,10 @@ import (
 )
 
 func producePrototypes(t *testing.T, filename string, mainFile string) ([]*Prototype, int) {
-	bytes, err := os.ReadFile(filepath.Join("test_data", filename))
+	bytes, err := os.ReadFile(filepath.Join("testdata", filename))
 	require.NoError(t, err)
 
-	parser := &CTagsParser{}
+	parser := &Parser{}
 	return parser.Parse(bytes, paths.New(mainFile))
 }
 
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserClassMembersAreFilteredOut.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserClassMembersAreFilteredOut.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserClassMembersAreFilteredOut.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserClassMembersAreFilteredOut.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserDefaultArguments.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserDefaultArguments.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserDefaultArguments.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserDefaultArguments.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserFunctionPointer.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointer.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserFunctionPointer.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointer.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserFunctionPointers.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointers.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserFunctionPointers.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointers.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserFunctionPointersNoIndirect.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointersNoIndirect.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserFunctionPointersNoIndirect.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserFunctionPointersNoIndirect.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserNamespace.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserNamespace.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserNamespace.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserNamespace.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldDealFunctionWithDifferentSignatures.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealFunctionWithDifferentSignatures.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldDealFunctionWithDifferentSignatures.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealFunctionWithDifferentSignatures.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithClasses.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithClasses.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithClasses.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithClasses.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithMacros.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithMacros.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithMacros.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithMacros.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithStructs.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithStructs.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldDealWithStructs.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldDealWithStructs.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldListPrototypes.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListPrototypes.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldListPrototypes.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListPrototypes.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldListTemplates.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListTemplates.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldListTemplates.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListTemplates.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserShouldListTemplates2.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListTemplates2.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserShouldListTemplates2.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserShouldListTemplates2.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserStatic.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserStatic.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserStatic.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserStatic.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsParserStructWithFunctions.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserStructWithFunctions.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsParserStructWithFunctions.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsParserStructWithFunctions.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsRunnerSketchWithClassFunction.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsRunnerSketchWithClassFunction.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsRunnerSketchWithClassFunction.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsRunnerSketchWithClassFunction.txt
diff --git a/legacy/builder/ctags/test_data/TestCTagsRunnerSketchWithMultifile.txt b/arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsRunnerSketchWithMultifile.txt
similarity index 100%
rename from legacy/builder/ctags/test_data/TestCTagsRunnerSketchWithMultifile.txt
rename to arduino/builder/preprocessor/internal/ctags/testdata/TestCTagsRunnerSketchWithMultifile.txt
diff --git a/arduino/builder/sketch.go b/arduino/builder/sketch.go
index 8560178a193..a79bbac4bef 100644
--- a/arduino/builder/sketch.go
+++ b/arduino/builder/sketch.go
@@ -20,6 +20,7 @@ import (
 	"fmt"
 	"regexp"
 
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
 	"github.com/arduino/arduino-cli/arduino/sketch"
 	"github.com/arduino/arduino-cli/i18n"
 	"github.com/arduino/go-paths-helper"
@@ -36,17 +37,16 @@ var (
 // PrepareSketchBuildPath copies the sketch source files in the build path.
 // The .ino files are merged together to create a .cpp file (by the way, the
 // .cpp file still needs to be Arduino-preprocessed to compile).
-func PrepareSketchBuildPath(sketch *sketch.Sketch, sourceOverrides map[string]string, buildPath *paths.Path) (offset int, mergedSource string, err error) {
-	if offset, mergedSource, err = sketchMergeSources(sketch, sourceOverrides); err != nil {
-		return
-	}
-	if err = SketchSaveItemCpp(sketch.MainFile, []byte(mergedSource), buildPath); err != nil {
-		return
-	}
-	if err = sketchCopyAdditionalFiles(sketch, buildPath, sourceOverrides); err != nil {
-		return
+func PrepareSketchBuildPath(sketch *sketch.Sketch, sourceOverrides map[string]string, buildPath *paths.Path) (int, error) {
+	if offset, mergedSource, err := sketchMergeSources(sketch, sourceOverrides); err != nil {
+		return 0, err
+	} else if err := SketchSaveItemCpp(sketch.MainFile, []byte(mergedSource), buildPath); err != nil {
+		return 0, err
+	} else if err := sketchCopyAdditionalFiles(sketch, buildPath, sourceOverrides); err != nil {
+		return 0, err
+	} else {
+		return offset, nil
 	}
-	return
 }
 
 // SketchSaveItemCpp saves a preprocessed .cpp sketch file on disk
@@ -96,7 +96,7 @@ func sketchMergeSources(sk *sketch.Sketch, overrides map[string]string) (int, st
 		lineOffset++
 	}
 
-	mergedSource += "#line 1 " + QuoteCppString(sk.MainFile.String()) + "\n"
+	mergedSource += "#line 1 " + cpp.QuoteString(sk.MainFile.String()) + "\n"
 	mergedSource += mainSrc + "\n"
 	lineOffset++
 
@@ -105,7 +105,7 @@ func sketchMergeSources(sk *sketch.Sketch, overrides map[string]string) (int, st
 		if err != nil {
 			return 0, "", err
 		}
-		mergedSource += "#line 1 " + QuoteCppString(file.String()) + "\n"
+		mergedSource += "#line 1 " + cpp.QuoteString(file.String()) + "\n"
 		mergedSource += src + "\n"
 	}
 
@@ -145,7 +145,7 @@ func sketchCopyAdditionalFiles(sketch *sketch.Sketch, destPath *paths.Path, over
 		}
 
 		// tag each addtional file with the filename of the source it was copied from
-		sourceBytes = append([]byte("#line 1 "+QuoteCppString(file.String())+"\n"), sourceBytes...)
+		sourceBytes = append([]byte("#line 1 "+cpp.QuoteString(file.String())+"\n"), sourceBytes...)
 
 		err = writeIfDifferent(sourceBytes, targetPath)
 		if err != nil {
diff --git a/internal/integrationtest/compile_1/compile_test.go b/internal/integrationtest/compile_1/compile_test.go
index dcfb8736f19..60c6552a678 100644
--- a/internal/integrationtest/compile_1/compile_test.go
+++ b/internal/integrationtest/compile_1/compile_test.go
@@ -25,7 +25,7 @@ import (
 	"testing"
 	"time"
 
-	"github.com/arduino/arduino-cli/arduino/builder"
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
 	"github.com/arduino/arduino-cli/internal/integrationtest"
 	"github.com/arduino/go-paths-helper"
 	"github.com/stretchr/testify/require"
@@ -1060,7 +1060,6 @@ func compileWithRelativeBuildPath(t *testing.T, env *integrationtest.Environment
 		"core",
 		"includes.cache",
 		"libraries",
-		"preproc",
 		"sketch",
 	}
 
@@ -1191,7 +1190,7 @@ void loop() {
 }
 
 `
-	expected = strings.ReplaceAll(expected, "%SKETCH_PATH%", builder.QuoteCppString(sketchPath.Join("SketchSimple.ino").String()))
+	expected = strings.ReplaceAll(expected, "%SKETCH_PATH%", cpp.QuoteString(sketchPath.Join("SketchSimple.ino").String()))
 
 	jsonOut, _, err := cli.Run("compile", "-b", fqbn, "--preprocess", sketchPath.String(), "--format", "json")
 	require.NoError(t, err)
diff --git a/legacy/builder/add_additional_entries_to_context.go b/legacy/builder/add_additional_entries_to_context.go
index fcb9639e37c..9e9fdd80669 100644
--- a/legacy/builder/add_additional_entries_to_context.go
+++ b/legacy/builder/add_additional_entries_to_context.go
@@ -26,10 +26,6 @@ type AddAdditionalEntriesToContext struct{}
 func (*AddAdditionalEntriesToContext) Run(ctx *types.Context) error {
 	if ctx.BuildPath != nil {
 		buildPath := ctx.BuildPath
-		preprocPath, err := buildPath.Join(constants.FOLDER_PREPROC).Abs()
-		if err != nil {
-			return errors.WithStack(err)
-		}
 		sketchBuildPath, err := buildPath.Join(constants.FOLDER_SKETCH).Abs()
 		if err != nil {
 			return errors.WithStack(err)
@@ -43,7 +39,6 @@ func (*AddAdditionalEntriesToContext) Run(ctx *types.Context) error {
 			return errors.WithStack(err)
 		}
 
-		ctx.PreprocPath = preprocPath
 		ctx.SketchBuildPath = sketchBuildPath
 		ctx.LibrariesBuildPath = librariesBuildPath
 		ctx.CoreBuildPath = coreBuildPath
diff --git a/legacy/builder/builder.go b/legacy/builder/builder.go
index b1b1f007c5d..fe11d684faa 100644
--- a/legacy/builder/builder.go
+++ b/legacy/builder/builder.go
@@ -20,6 +20,7 @@ import (
 	"time"
 
 	"github.com/arduino/arduino-cli/arduino/builder"
+	"github.com/arduino/arduino-cli/arduino/builder/preprocessor"
 	"github.com/arduino/arduino-cli/i18n"
 	"github.com/arduino/arduino-cli/legacy/builder/phases"
 	"github.com/arduino/arduino-cli/legacy/builder/types"
@@ -49,7 +50,7 @@ func (s *Builder) Run(ctx *types.Context) error {
 		&RecipeByPrefixSuffixRunner{Prefix: "recipe.hooks.prebuild", Suffix: ".pattern"},
 
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = builder.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = builder.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 
@@ -59,7 +60,7 @@ func (s *Builder) Run(ctx *types.Context) error {
 		&WarnAboutArchIncompatibleLibraries{},
 
 		utils.LogIfVerbose(false, tr("Generating function prototypes...")),
-		&PreprocessSketch{},
+		types.BareCommand(PreprocessSketch),
 
 		utils.LogIfVerbose(false, tr("Compiling sketch...")),
 		&RecipeByPrefixSuffixRunner{Prefix: "recipe.hooks.sketch.prebuild", Suffix: ".pattern"},
@@ -115,13 +116,19 @@ func (s *Builder) Run(ctx *types.Context) error {
 	return otherErr
 }
 
-type PreprocessSketch struct{}
-
-func (s *PreprocessSketch) Run(ctx *types.Context) error {
+func PreprocessSketch(ctx *types.Context) error {
 	if ctx.UseArduinoPreprocessor {
 		return PreprocessSketchWithArduinoPreprocessor(ctx)
 	} else {
-		return PreprocessSketchWithCtags(ctx)
+		normalOutput, verboseOutput, err := preprocessor.PreprocessSketchWithCtags(
+			ctx.Sketch, ctx.BuildPath, ctx.IncludeFolders, ctx.LineOffset,
+			ctx.BuildProperties, ctx.OnlyUpdateCompilationDatabase)
+		if ctx.Verbose {
+			ctx.WriteStdout(verboseOutput)
+		} else {
+			ctx.WriteStdout(normalOutput)
+		}
+		return err
 	}
 }
 
@@ -141,7 +148,7 @@ func (s *Preprocess) Run(ctx *types.Context) error {
 		&RecipeByPrefixSuffixRunner{Prefix: "recipe.hooks.prebuild", Suffix: ".pattern"},
 
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = builder.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = builder.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 
@@ -149,7 +156,7 @@ func (s *Preprocess) Run(ctx *types.Context) error {
 
 		&WarnAboutArchIncompatibleLibraries{},
 
-		&PreprocessSketch{},
+		types.BareCommand(PreprocessSketch),
 	}
 
 	if err := runCommands(ctx, commands); err != nil {
@@ -157,7 +164,11 @@ func (s *Preprocess) Run(ctx *types.Context) error {
 	}
 
 	// Output arduino-preprocessed source
-	ctx.WriteStdout([]byte(ctx.SketchSourceAfterArduinoPreprocessing))
+	preprocessedSketch, err := ctx.SketchBuildPath.Join(ctx.Sketch.MainFile.Base() + ".cpp").ReadFile()
+	if err != nil {
+		return err
+	}
+	ctx.WriteStdout(preprocessedSketch)
 	return nil
 }
 
diff --git a/legacy/builder/constants/constants.go b/legacy/builder/constants/constants.go
index 36d11764ebc..a91f454ffcf 100644
--- a/legacy/builder/constants/constants.go
+++ b/legacy/builder/constants/constants.go
@@ -34,7 +34,6 @@ const BUILD_PROPERTIES_RUNTIME_PLATFORM_PATH = "runtime.platform.path"
 const EMPTY_STRING = ""
 const FOLDER_BOOTLOADERS = "bootloaders"
 const FOLDER_CORE = "core"
-const FOLDER_PREPROC = "preproc"
 const FOLDER_SKETCH = "sketch"
 const FOLDER_TOOLS = "tools"
 const FOLDER_LIBRARIES = "libraries"
diff --git a/legacy/builder/container_add_prototypes.go b/legacy/builder/container_add_prototypes.go
deleted file mode 100644
index 288bb03e1f4..00000000000
--- a/legacy/builder/container_add_prototypes.go
+++ /dev/null
@@ -1,144 +0,0 @@
-// This file is part of arduino-cli.
-//
-// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
-//
-// This software is released under the GNU General Public License version 3,
-// which covers the main part of arduino-cli.
-// The terms of this license can be found at:
-// https://www.gnu.org/licenses/gpl-3.0.en.html
-//
-// You can be released from the requirements of the above licenses by purchasing
-// a commercial license. Buying such a license is mandatory if you want to
-// modify or otherwise use the software for commercial activities involving the
-// Arduino software without disclosing the source code of your own applications.
-// To purchase a commercial license, send an email to license@arduino.cc.
-
-package builder
-
-import (
-	"bufio"
-	"bytes"
-	"fmt"
-	"io"
-	"strconv"
-	"strings"
-
-	bldr "github.com/arduino/arduino-cli/arduino/builder"
-	"github.com/arduino/arduino-cli/arduino/builder/preprocessor"
-	"github.com/arduino/arduino-cli/arduino/sketch"
-	"github.com/arduino/arduino-cli/legacy/builder/types"
-	"github.com/arduino/go-paths-helper"
-	"github.com/pkg/errors"
-)
-
-func PreprocessSketchWithCtags(ctx *types.Context) error {
-	// Generate the full pathname for the preproc output file
-	if err := ctx.PreprocPath.MkdirAll(); err != nil {
-		return errors.WithStack(err)
-	}
-	targetFilePath := ctx.PreprocPath.Join("sketch_merged.cpp")
-
-	// Run preprocessor
-	sourceFile := ctx.SketchBuildPath.Join(ctx.Sketch.MainFile.Base() + ".cpp")
-	gccStdout, gccStderr, err := preprocessor.GCC(sourceFile, targetFilePath, ctx.IncludeFolders, ctx.BuildProperties)
-	if ctx.Verbose {
-		ctx.WriteStdout(gccStdout)
-		ctx.WriteStderr(gccStderr)
-	}
-	if err != nil {
-		if !ctx.OnlyUpdateCompilationDatabase {
-			return errors.WithStack(err)
-		}
-
-		// Do not bail out if we are generating the compile commands database
-		ctx.Info(
-			fmt.Sprintf("%s: %s",
-				tr("An error occurred adding prototypes"),
-				tr("the compilation database may be incomplete or inaccurate")))
-		if err := sourceFile.CopyTo(targetFilePath); err != nil {
-			return errors.WithStack(err)
-		}
-	}
-
-	if src, err := targetFilePath.ReadFile(); err != nil {
-		return err
-	} else {
-		ctx.SketchSourceAfterCppPreprocessing = filterSketchSource(ctx.Sketch, bytes.NewReader(src), false)
-	}
-
-	if err := targetFilePath.WriteFile([]byte(ctx.SketchSourceAfterCppPreprocessing)); err != nil {
-		return err
-	}
-
-	ctagsStdout, ctagsStderr, err := preprocessor.RunCTags(targetFilePath, ctx.BuildProperties)
-	if ctx.Verbose {
-		ctx.WriteStderr(ctagsStderr)
-	}
-	if err != nil {
-		return err
-	}
-	ctx.SketchSourceAfterArduinoPreprocessing = PrototypesAdder(ctx.Sketch, ctx.SketchSourceMerged, ctagsStdout, ctx.LineOffset)
-
-	if err := bldr.SketchSaveItemCpp(ctx.Sketch.MainFile, []byte(ctx.SketchSourceAfterArduinoPreprocessing), ctx.SketchBuildPath); err != nil {
-		return errors.WithStack(err)
-	}
-
-	return nil
-}
-
-func filterSketchSource(sketch *sketch.Sketch, source io.Reader, removeLineMarkers bool) string {
-	fileNames := paths.NewPathList()
-	fileNames.Add(sketch.MainFile)
-	fileNames.AddAll(sketch.OtherSketchFiles)
-
-	inSketch := false
-	filtered := ""
-
-	scanner := bufio.NewScanner(source)
-	for scanner.Scan() {
-		line := scanner.Text()
-		if filename := parseLineMarker(line); filename != nil {
-			inSketch = fileNames.Contains(filename)
-			if inSketch && removeLineMarkers {
-				continue
-			}
-		}
-
-		if inSketch {
-			filtered += line + "\n"
-		}
-	}
-
-	return filtered
-}
-
-// Parses the given line as a gcc line marker and returns the contained
-// filename.
-func parseLineMarker(line string) *paths.Path {
-	// A line marker contains the line number and filename and looks like:
-	// # 123 /path/to/file.cpp
-	// It can be followed by zero or more flag number that indicate the
-	// preprocessor state and can be ignored.
-	// For exact details on this format, see:
-	// https://github.com/gcc-mirror/gcc/blob/edd716b6b1caa1a5cb320a8cd7f626f30198e098/gcc/c-family/c-ppoutput.c#L413-L415
-
-	split := strings.SplitN(line, " ", 3)
-	if len(split) < 3 || len(split[0]) == 0 || split[0][0] != '#' {
-		return nil
-	}
-
-	_, err := strconv.Atoi(split[1])
-	if err != nil {
-		return nil
-	}
-
-	// If we get here, we found a # followed by a line number, so
-	// assume this is a line marker and see if the rest of the line
-	// starts with a string containing the filename
-	str, rest, ok := bldr.ParseCppString(split[2])
-
-	if ok && (rest == "" || rest[0] == ' ') {
-		return paths.New(str)
-	}
-	return nil
-}
diff --git a/legacy/builder/create_cmake_rule.go b/legacy/builder/create_cmake_rule.go
index 394b80ec49f..9cc38434286 100644
--- a/legacy/builder/create_cmake_rule.go
+++ b/legacy/builder/create_cmake_rule.go
@@ -115,7 +115,7 @@ func (s *ExportProjectCMake) Run(ctx *types.Context) error {
 		fmt.Println(err)
 	}
 
-	if err := PreprocessSketchWithCtags(ctx); err != nil {
+	if err := PreprocessSketch(ctx); err != nil {
 		return err
 	}
 
diff --git a/legacy/builder/preprocess_sketch.go b/legacy/builder/preprocess_sketch.go
index 7f8aaccec38..7dff77c7dde 100644
--- a/legacy/builder/preprocess_sketch.go
+++ b/legacy/builder/preprocess_sketch.go
@@ -31,12 +31,12 @@ import (
 )
 
 func PreprocessSketchWithArduinoPreprocessor(ctx *types.Context) error {
-	if err := ctx.PreprocPath.MkdirAll(); err != nil {
+	if err := ctx.BuildPath.Join("preproc").MkdirAll(); err != nil {
 		return errors.WithStack(err)
 	}
 
 	sourceFile := ctx.SketchBuildPath.Join(ctx.Sketch.MainFile.Base() + ".cpp")
-	targetFile := ctx.PreprocPath.Join("sketch_merged.cpp")
+	targetFile := ctx.BuildPath.Join("preproc", "sketch_merged.cpp")
 	gccStdout, gccStderr, err := preprocessor.GCC(sourceFile, targetFile, ctx.IncludeFolders, ctx.BuildProperties)
 	if ctx.Verbose {
 		ctx.WriteStdout(gccStdout)
@@ -85,8 +85,5 @@ func PreprocessSketchWithArduinoPreprocessor(ctx *types.Context) error {
 	}
 
 	result := utils.NormalizeUTF8(buf)
-
-	//fmt.Printf("PREPROCESSOR OUTPUT:\n%s\n", output)
-	ctx.SketchSourceAfterArduinoPreprocessing = string(result)
-	return bldr.SketchSaveItemCpp(ctx.Sketch.MainFile, []byte(ctx.SketchSourceAfterArduinoPreprocessing), ctx.SketchBuildPath)
+	return bldr.SketchSaveItemCpp(ctx.Sketch.MainFile, result, ctx.SketchBuildPath)
 }
diff --git a/legacy/builder/prototypes_adder.go b/legacy/builder/prototypes_adder.go
deleted file mode 100644
index e62a8486fa8..00000000000
--- a/legacy/builder/prototypes_adder.go
+++ /dev/null
@@ -1,105 +0,0 @@
-// This file is part of arduino-cli.
-//
-// Copyright 2020 ARDUINO SA (http://www.arduino.cc/)
-//
-// This software is released under the GNU General Public License version 3,
-// which covers the main part of arduino-cli.
-// The terms of this license can be found at:
-// https://www.gnu.org/licenses/gpl-3.0.en.html
-//
-// You can be released from the requirements of the above licenses by purchasing
-// a commercial license. Buying such a license is mandatory if you want to
-// modify or otherwise use the software for commercial activities involving the
-// Arduino software without disclosing the source code of your own applications.
-// To purchase a commercial license, send an email to license@arduino.cc.
-
-package builder
-
-import (
-	"fmt"
-	"strconv"
-	"strings"
-
-	"github.com/arduino/arduino-cli/arduino/sketch"
-	"github.com/arduino/arduino-cli/legacy/builder/constants"
-	"github.com/arduino/arduino-cli/legacy/builder/ctags"
-	"github.com/arduino/arduino-cli/legacy/builder/utils"
-)
-
-var DebugPreprocessor bool
-
-func PrototypesAdder(sketch *sketch.Sketch, source string, ctagsStdout []byte, lineOffset int) string {
-	parser := &ctags.CTagsParser{}
-	prototypes, firstFunctionLine := parser.Parse(ctagsStdout, sketch.MainFile)
-	if firstFunctionLine == -1 {
-		firstFunctionLine = 0
-	}
-
-	source = strings.Replace(source, "\r\n", "\n", -1)
-	source = strings.Replace(source, "\r", "\n", -1)
-	sourceRows := strings.Split(source, "\n")
-	if isFirstFunctionOutsideOfSource(firstFunctionLine, sourceRows) {
-		return ""
-	}
-
-	insertionLine := firstFunctionLine + lineOffset - 1
-	firstFunctionChar := len(strings.Join(sourceRows[:insertionLine], "\n")) + 1
-	prototypeSection := composePrototypeSection(firstFunctionLine, prototypes)
-	preprocessedSource := source[:firstFunctionChar] + prototypeSection + source[firstFunctionChar:]
-
-	if DebugPreprocessor {
-		fmt.Println("#PREPROCESSED SOURCE")
-		prototypesRows := strings.Split(prototypeSection, "\n")
-		prototypesRows = prototypesRows[:len(prototypesRows)-1]
-		for i := 0; i < len(sourceRows)+len(prototypesRows); i++ {
-			if i < insertionLine {
-				fmt.Printf("   |%s\n", sourceRows[i])
-			} else if i < insertionLine+len(prototypesRows) {
-				fmt.Printf("PRO|%s\n", prototypesRows[i-insertionLine])
-			} else {
-				fmt.Printf("   |%s\n", sourceRows[i-len(prototypesRows)])
-			}
-		}
-		fmt.Println("#END OF PREPROCESSED SOURCE")
-	}
-	return preprocessedSource
-}
-
-func composePrototypeSection(line int, prototypes []*ctags.Prototype) string {
-	if len(prototypes) == 0 {
-		return constants.EMPTY_STRING
-	}
-
-	str := joinPrototypes(prototypes)
-	str += "\n#line "
-	str += strconv.Itoa(line)
-	str += " " + utils.QuoteCppString(prototypes[0].File)
-	str += "\n"
-
-	return str
-}
-
-func joinPrototypes(prototypes []*ctags.Prototype) string {
-	prototypesSlice := []string{}
-	for _, proto := range prototypes {
-		if signatureContainsaDefaultArg(proto) {
-			continue
-		}
-		prototypesSlice = append(prototypesSlice, "#line "+strconv.Itoa(proto.Line)+" "+utils.QuoteCppString(proto.File))
-		prototypeParts := []string{}
-		if proto.Modifiers != "" {
-			prototypeParts = append(prototypeParts, proto.Modifiers)
-		}
-		prototypeParts = append(prototypeParts, proto.Prototype)
-		prototypesSlice = append(prototypesSlice, strings.Join(prototypeParts, " "))
-	}
-	return strings.Join(prototypesSlice, "\n")
-}
-
-func signatureContainsaDefaultArg(proto *ctags.Prototype) bool {
-	return strings.Contains(proto.Prototype, "=")
-}
-
-func isFirstFunctionOutsideOfSource(firstFunctionLine int, sourceRows []string) bool {
-	return firstFunctionLine > len(sourceRows)-1
-}
diff --git a/legacy/builder/test/add_additional_entries_to_context_test.go b/legacy/builder/test/add_additional_entries_to_context_test.go
index 51e5452daf3..fc1edb5acb2 100644
--- a/legacy/builder/test/add_additional_entries_to_context_test.go
+++ b/legacy/builder/test/add_additional_entries_to_context_test.go
@@ -31,7 +31,6 @@ func TestAddAdditionalEntriesToContextNoBuildPath(t *testing.T) {
 	command := builder.AddAdditionalEntriesToContext{}
 	NoError(t, command.Run(ctx))
 
-	require.Empty(t, ctx.PreprocPath)
 	require.Empty(t, ctx.SketchBuildPath)
 	require.Empty(t, ctx.LibrariesBuildPath)
 	require.Empty(t, ctx.CoreBuildPath)
@@ -48,7 +47,6 @@ func TestAddAdditionalEntriesToContextWithBuildPath(t *testing.T) {
 	command := builder.AddAdditionalEntriesToContext{}
 	NoError(t, command.Run(ctx))
 
-	require.Equal(t, Abs(t, paths.New("folder", constants.FOLDER_PREPROC)), ctx.PreprocPath)
 	require.Equal(t, Abs(t, paths.New("folder", constants.FOLDER_SKETCH)), ctx.SketchBuildPath)
 	require.Equal(t, Abs(t, paths.New("folder", "libraries")), ctx.LibrariesBuildPath)
 	require.Equal(t, Abs(t, paths.New("folder", constants.FOLDER_CORE)), ctx.CoreBuildPath)
diff --git a/legacy/builder/test/builder_test.go b/legacy/builder/test/builder_test.go
index e84e2d402dd..3d5740d659d 100644
--- a/legacy/builder/test/builder_test.go
+++ b/legacy/builder/test/builder_test.go
@@ -116,9 +116,6 @@ func TestBuilderEmptySketch(t *testing.T) {
 	exist, err := buildPath.Join(constants.FOLDER_CORE, "HardwareSerial.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "sketch1.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
@@ -143,9 +140,6 @@ func TestBuilderBridge(t *testing.T) {
 	exist, err := buildPath.Join(constants.FOLDER_CORE, "HardwareSerial.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "Bridge.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
@@ -173,9 +167,6 @@ func TestBuilderSketchWithConfig(t *testing.T) {
 	exist, err := buildPath.Join(constants.FOLDER_CORE, "HardwareSerial.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "sketch_with_config.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
@@ -208,9 +199,6 @@ func TestBuilderBridgeTwice(t *testing.T) {
 	exist, err := buildPath.Join(constants.FOLDER_CORE, "HardwareSerial.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "Bridge.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
@@ -245,9 +233,6 @@ func TestBuilderBridgeSAM(t *testing.T) {
 	exist, err = buildPath.Join(constants.FOLDER_CORE, "avr", "dtostrf.c.d").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "Bridge.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
@@ -286,9 +271,6 @@ func TestBuilderBridgeRedBearLab(t *testing.T) {
 	exist, err := buildPath.Join(constants.FOLDER_CORE, "HardwareSerial.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
-	exist, err = buildPath.Join(constants.FOLDER_PREPROC, "sketch_merged.cpp").ExistCheck()
-	NoError(t, err)
-	require.True(t, exist)
 	exist, err = buildPath.Join(constants.FOLDER_SKETCH, "Bridge.ino.cpp.o").ExistCheck()
 	NoError(t, err)
 	require.True(t, exist)
diff --git a/legacy/builder/test/ctags_runner_test.go b/legacy/builder/test/ctags_runner_test.go
index d776a93c4bc..557aa34f57d 100644
--- a/legacy/builder/test/ctags_runner_test.go
+++ b/legacy/builder/test/ctags_runner_test.go
@@ -34,9 +34,10 @@ func ctagsRunnerTestTemplate(t *testing.T, sketchLocation *paths.Path) []byte {
 	err := (&builder.ContainerSetupHardwareToolsLibsSketchAndProps{}).Run(ctx)
 	NoError(t, err)
 
-	_, source, err := bldr.PrepareSketchBuildPath(ctx.Sketch, nil, ctx.SketchBuildPath)
+	_, err = bldr.PrepareSketchBuildPath(ctx.Sketch, nil, ctx.SketchBuildPath)
 	NoError(t, err)
 
+	source := loadPreprocessedSketch(t, ctx)
 	target := ctx.BuildPath.Join("ctags_target.cpp")
 	NoError(t, target.WriteFile([]byte(source)))
 
diff --git a/legacy/builder/test/helper.go b/legacy/builder/test/helper.go
index 4581dd7c921..88432e5fc76 100644
--- a/legacy/builder/test/helper.go
+++ b/legacy/builder/test/helper.go
@@ -23,11 +23,11 @@ import (
 	"testing"
 	"text/template"
 
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
 	"github.com/arduino/arduino-cli/arduino/cores"
 	"github.com/arduino/arduino-cli/arduino/libraries"
 	"github.com/arduino/arduino-cli/legacy/builder/constants"
 	"github.com/arduino/arduino-cli/legacy/builder/types"
-	"github.com/arduino/arduino-cli/legacy/builder/utils"
 	paths "github.com/arduino/go-paths-helper"
 	"github.com/stretchr/testify/assert"
 	"github.com/stretchr/testify/require"
@@ -35,7 +35,7 @@ import (
 
 func LoadAndInterpolate(t *testing.T, filename string, ctx *types.Context) string {
 	funcsMap := template.FuncMap{
-		"QuoteCppString": utils.QuoteCppPath,
+		"QuoteCppString": func(p *paths.Path) string { return cpp.QuoteString(p.String()) },
 	}
 
 	tpl, err := template.New(filepath.Base(filename)).Funcs(funcsMap).ParseFiles(filename)
diff --git a/legacy/builder/test/includes_to_include_folders_test.go b/legacy/builder/test/includes_to_include_folders_test.go
index a19d0ad57f2..f457e518185 100644
--- a/legacy/builder/test/includes_to_include_folders_test.go
+++ b/legacy/builder/test/includes_to_include_folders_test.go
@@ -36,7 +36,7 @@ func TestIncludesToIncludeFolders(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -60,7 +60,7 @@ func TestIncludesToIncludeFoldersSketchWithIfDef(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -83,7 +83,7 @@ func TestIncludesToIncludeFoldersIRremoteLibrary(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -109,7 +109,7 @@ func TestIncludesToIncludeFoldersANewLibrary(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -140,7 +140,7 @@ func TestIncludesToIncludeFoldersDuplicateLibs(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -172,7 +172,7 @@ func TestIncludesToIncludeFoldersDuplicateLibsWithConflictingLibsOutsideOfPlatfo
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -204,7 +204,7 @@ func TestIncludesToIncludeFoldersDuplicateLibs2(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -230,7 +230,7 @@ func TestIncludesToIncludeFoldersSubfolders(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
diff --git a/legacy/builder/test/prototypes_adder_test.go b/legacy/builder/test/prototypes_adder_test.go
index 64630a7ba70..024d86cf265 100644
--- a/legacy/builder/test/prototypes_adder_test.go
+++ b/legacy/builder/test/prototypes_adder_test.go
@@ -22,16 +22,22 @@ import (
 	"testing"
 
 	bldr "github.com/arduino/arduino-cli/arduino/builder"
+	"github.com/arduino/arduino-cli/arduino/builder/cpp"
 	"github.com/arduino/arduino-cli/legacy/builder"
 	"github.com/arduino/arduino-cli/legacy/builder/types"
-	"github.com/arduino/arduino-cli/legacy/builder/utils"
 	paths "github.com/arduino/go-paths-helper"
 	"github.com/stretchr/testify/require"
 )
 
+func loadPreprocessedSketch(t *testing.T, ctx *types.Context) string {
+	res, err := ctx.SketchBuildPath.Join(ctx.Sketch.MainFile.Base() + ".cpp").ReadFile()
+	NoError(t, err)
+	return string(res)
+}
+
 func TestPrototypesAdderBridgeExample(t *testing.T) {
 	sketchLocation := paths.New("downloaded_libraries", "Bridge", "examples", "Bridge", "Bridge.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -42,7 +48,7 @@ func TestPrototypesAdderBridgeExample(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -51,10 +57,11 @@ func TestPrototypesAdderBridgeExample(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 33 "+quotedSketchLocation+"\nvoid setup();\n#line 46 "+quotedSketchLocation+"\nvoid loop();\n#line 62 "+quotedSketchLocation+"\nvoid process(BridgeClient client);\n#line 82 "+quotedSketchLocation+"\nvoid digitalCommand(BridgeClient client);\n#line 109 "+quotedSketchLocation+"\nvoid analogCommand(BridgeClient client);\n#line 149 "+quotedSketchLocation+"\nvoid modeCommand(BridgeClient client);\n#line 33 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 33 "+quotedSketchLocation+"\nvoid setup();\n#line 46 "+quotedSketchLocation+"\nvoid loop();\n#line 62 "+quotedSketchLocation+"\nvoid process(BridgeClient client);\n#line 82 "+quotedSketchLocation+"\nvoid digitalCommand(BridgeClient client);\n#line 109 "+quotedSketchLocation+"\nvoid analogCommand(BridgeClient client);\n#line 149 "+quotedSketchLocation+"\nvoid modeCommand(BridgeClient client);\n#line 33 "+quotedSketchLocation+"\n")
 }
 
 func TestPrototypesAdderSketchWithIfDef(t *testing.T) {
@@ -67,7 +74,7 @@ func TestPrototypesAdderSketchWithIfDef(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -76,10 +83,11 @@ func TestPrototypesAdderSketchWithIfDef(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("SketchWithIfDef", "SketchWithIfDef.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderBaladuino(t *testing.T) {
@@ -92,7 +100,7 @@ func TestPrototypesAdderBaladuino(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -101,10 +109,11 @@ func TestPrototypesAdderBaladuino(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("Baladuino", "Baladuino.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderCharWithEscapedDoubleQuote(t *testing.T) {
@@ -117,7 +126,7 @@ func TestPrototypesAdderCharWithEscapedDoubleQuote(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -126,10 +135,11 @@ func TestPrototypesAdderCharWithEscapedDoubleQuote(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("CharWithEscapedDoubleQuote", "CharWithEscapedDoubleQuote.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderIncludeBetweenMultilineComment(t *testing.T) {
@@ -142,7 +152,7 @@ func TestPrototypesAdderIncludeBetweenMultilineComment(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -151,10 +161,11 @@ func TestPrototypesAdderIncludeBetweenMultilineComment(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("IncludeBetweenMultilineComment", "IncludeBetweenMultilineComment.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderLineContinuations(t *testing.T) {
@@ -167,7 +178,7 @@ func TestPrototypesAdderLineContinuations(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -176,10 +187,11 @@ func TestPrototypesAdderLineContinuations(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("LineContinuations", "LineContinuations.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderStringWithComment(t *testing.T) {
@@ -192,7 +204,7 @@ func TestPrototypesAdderStringWithComment(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -201,10 +213,11 @@ func TestPrototypesAdderStringWithComment(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("StringWithComment", "StringWithComment.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderSketchWithStruct(t *testing.T) {
@@ -217,7 +230,7 @@ func TestPrototypesAdderSketchWithStruct(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -226,10 +239,11 @@ func TestPrototypesAdderSketchWithStruct(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("SketchWithStruct", "SketchWithStruct.preprocessed.txt"), ctx)
-	obtained := strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1)
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	obtained := strings.Replace(preprocessedSketch, "\r\n", "\n", -1)
 	// ctags based preprocessing removes the space after "dostuff", but this is still OK
 	// TODO: remove this exception when moving to a more powerful parser
 	preprocessed = strings.Replace(preprocessed, "void dostuff (A_NEW_TYPE * bar);", "void dostuff(A_NEW_TYPE * bar);", 1)
@@ -239,7 +253,7 @@ func TestPrototypesAdderSketchWithStruct(t *testing.T) {
 
 func TestPrototypesAdderSketchWithConfig(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_config", "sketch_with_config.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -250,7 +264,7 @@ func TestPrototypesAdderSketchWithConfig(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -259,18 +273,19 @@ func TestPrototypesAdderSketchWithConfig(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 13 "+quotedSketchLocation+"\nvoid setup();\n#line 17 "+quotedSketchLocation+"\nvoid loop();\n#line 13 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 13 "+quotedSketchLocation+"\nvoid setup();\n#line 17 "+quotedSketchLocation+"\nvoid loop();\n#line 13 "+quotedSketchLocation+"\n")
 
 	preprocessed := LoadAndInterpolate(t, filepath.Join("sketch_with_config", "sketch_with_config.preprocessed.txt"), ctx)
-	require.Equal(t, preprocessed, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	require.Equal(t, preprocessed, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderSketchNoFunctionsTwoFiles(t *testing.T) {
 	sketchLocation := paths.New("sketch_no_functions_two_files", "sketch_no_functions_two_files.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, paths.New("sketch_no_functions_two_files", "sketch_no_functions_two_files.ino"), "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -281,7 +296,7 @@ func TestPrototypesAdderSketchNoFunctionsTwoFiles(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -290,10 +305,12 @@ func TestPrototypesAdderSketchNoFunctionsTwoFiles(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	mergedSketch := loadPreprocessedSketch(t, ctx)
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Equal(t, ctx.SketchSourceMerged, ctx.SketchSourceAfterArduinoPreprocessing) // No prototypes added
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Equal(t, mergedSketch, preprocessedSketch) // No prototypes added
 }
 
 func TestPrototypesAdderSketchNoFunctions(t *testing.T) {
@@ -303,12 +320,12 @@ func TestPrototypesAdderSketchNoFunctions(t *testing.T) {
 	ctx.Verbose = true
 
 	sketchLocation := paths.New("sketch_no_functions", "sketch_no_functions.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 	var _err error
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -317,15 +334,17 @@ func TestPrototypesAdderSketchNoFunctions(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	mergedSketch := loadPreprocessedSketch(t, ctx)
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Equal(t, ctx.SketchSourceMerged, ctx.SketchSourceAfterArduinoPreprocessing) // No prototypes added
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Equal(t, mergedSketch, preprocessedSketch) // No prototypes added
 }
 
 func TestPrototypesAdderSketchWithDefaultArgs(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_default_args", "sketch_with_default_args.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -336,7 +355,7 @@ func TestPrototypesAdderSketchWithDefaultArgs(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -345,15 +364,16 @@ func TestPrototypesAdderSketchWithDefaultArgs(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 4 "+quotedSketchLocation+"\nvoid setup();\n#line 7 "+quotedSketchLocation+"\nvoid loop();\n#line 1 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 4 "+quotedSketchLocation+"\nvoid setup();\n#line 7 "+quotedSketchLocation+"\nvoid loop();\n#line 1 "+quotedSketchLocation+"\n")
 }
 
 func TestPrototypesAdderSketchWithInlineFunction(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_inline_function", "sketch_with_inline_function.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -364,7 +384,7 @@ func TestPrototypesAdderSketchWithInlineFunction(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -373,12 +393,13 @@ func TestPrototypesAdderSketchWithInlineFunction(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
 
 	expected := "#line 1 " + quotedSketchLocation + "\nvoid setup();\n#line 2 " + quotedSketchLocation + "\nvoid loop();\n#line 4 " + quotedSketchLocation + "\nshort unsigned int testInt();\n#line 8 " + quotedSketchLocation + "\nstatic int8_t testInline();\n#line 12 " + quotedSketchLocation + "\n__attribute__((always_inline)) uint8_t testAttribute();\n#line 1 " + quotedSketchLocation + "\n"
-	obtained := ctx.SketchSourceAfterArduinoPreprocessing
+	obtained := preprocessedSketch
 	// ctags based preprocessing removes "inline" but this is still OK
 	// TODO: remove this exception when moving to a more powerful parser
 	expected = strings.Replace(expected, "static inline int8_t testInline();", "static int8_t testInline();", -1)
@@ -392,7 +413,7 @@ func TestPrototypesAdderSketchWithInlineFunction(t *testing.T) {
 
 func TestPrototypesAdderSketchWithFunctionSignatureInsideIFDEF(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_function_signature_inside_ifdef", "sketch_with_function_signature_inside_ifdef.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:leonardo")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -403,7 +424,7 @@ func TestPrototypesAdderSketchWithFunctionSignatureInsideIFDEF(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -412,15 +433,16 @@ func TestPrototypesAdderSketchWithFunctionSignatureInsideIFDEF(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 1 "+quotedSketchLocation+"\nvoid setup();\n#line 3 "+quotedSketchLocation+"\nvoid loop();\n#line 15 "+quotedSketchLocation+"\nint8_t adalight();\n#line 1 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 1 "+quotedSketchLocation+"\nvoid setup();\n#line 3 "+quotedSketchLocation+"\nvoid loop();\n#line 15 "+quotedSketchLocation+"\nint8_t adalight();\n#line 1 "+quotedSketchLocation+"\n")
 }
 
 func TestPrototypesAdderSketchWithUSBCON(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_usbcon", "sketch_with_usbcon.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := &types.Context{
 		HardwareDirs:         paths.NewPathList(filepath.Join("..", "hardware"), "downloaded_hardware"),
@@ -436,7 +458,7 @@ func TestPrototypesAdderSketchWithUSBCON(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -445,15 +467,16 @@ func TestPrototypesAdderSketchWithUSBCON(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 5 "+quotedSketchLocation+"\nvoid ciao();\n#line 10 "+quotedSketchLocation+"\nvoid setup();\n#line 15 "+quotedSketchLocation+"\nvoid loop();\n#line 5 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 5 "+quotedSketchLocation+"\nvoid ciao();\n#line 10 "+quotedSketchLocation+"\nvoid setup();\n#line 15 "+quotedSketchLocation+"\nvoid loop();\n#line 5 "+quotedSketchLocation+"\n")
 }
 
 func TestPrototypesAdderSketchWithTypename(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_typename", "sketch_with_typename.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := &types.Context{
 		HardwareDirs:         paths.NewPathList(filepath.Join("..", "hardware"), "downloaded_hardware"),
@@ -468,7 +491,7 @@ func TestPrototypesAdderSketchWithTypename(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -477,11 +500,12 @@ func TestPrototypesAdderSketchWithTypename(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
 	expected := "#line 6 " + quotedSketchLocation + "\nvoid setup();\n#line 10 " + quotedSketchLocation + "\nvoid loop();\n#line 12 " + quotedSketchLocation + "\ntypename Foo<char>::Bar func();\n#line 6 " + quotedSketchLocation + "\n"
-	obtained := ctx.SketchSourceAfterArduinoPreprocessing
+	obtained := preprocessedSketch
 	// ctags based preprocessing ignores line with typename
 	// TODO: remove this exception when moving to a more powerful parser
 	expected = strings.Replace(expected, "#line 12 "+quotedSketchLocation+"\ntypename Foo<char>::Bar func();\n", "", -1)
@@ -491,7 +515,7 @@ func TestPrototypesAdderSketchWithTypename(t *testing.T) {
 
 func TestPrototypesAdderSketchWithIfDef2(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_ifdef", "sketch_with_ifdef.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:yun")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -502,7 +526,7 @@ func TestPrototypesAdderSketchWithIfDef2(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -511,18 +535,19 @@ func TestPrototypesAdderSketchWithIfDef2(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 5 "+quotedSketchLocation+"\nvoid elseBranch();\n#line 9 "+quotedSketchLocation+"\nvoid f1();\n#line 10 "+quotedSketchLocation+"\nvoid f2();\n#line 12 "+quotedSketchLocation+"\nvoid setup();\n#line 14 "+quotedSketchLocation+"\nvoid loop();\n#line 5 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 5 "+quotedSketchLocation+"\nvoid elseBranch();\n#line 9 "+quotedSketchLocation+"\nvoid f1();\n#line 10 "+quotedSketchLocation+"\nvoid f2();\n#line 12 "+quotedSketchLocation+"\nvoid setup();\n#line 14 "+quotedSketchLocation+"\nvoid loop();\n#line 5 "+quotedSketchLocation+"\n")
 
 	expectedSource := LoadAndInterpolate(t, filepath.Join("sketch_with_ifdef", "sketch.preprocessed.txt"), ctx)
-	require.Equal(t, expectedSource, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	require.Equal(t, expectedSource, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderSketchWithIfDef2SAM(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_ifdef", "sketch_with_ifdef.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:sam:arduino_due_x_dbg")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -533,7 +558,7 @@ func TestPrototypesAdderSketchWithIfDef2SAM(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -542,18 +567,19 @@ func TestPrototypesAdderSketchWithIfDef2SAM(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 2 "+quotedSketchLocation+"\nvoid ifBranch();\n#line 9 "+quotedSketchLocation+"\nvoid f1();\n#line 10 "+quotedSketchLocation+"\nvoid f2();\n#line 12 "+quotedSketchLocation+"\nvoid setup();\n#line 14 "+quotedSketchLocation+"\nvoid loop();\n#line 2 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 2 "+quotedSketchLocation+"\nvoid ifBranch();\n#line 9 "+quotedSketchLocation+"\nvoid f1();\n#line 10 "+quotedSketchLocation+"\nvoid f2();\n#line 12 "+quotedSketchLocation+"\nvoid setup();\n#line 14 "+quotedSketchLocation+"\nvoid loop();\n#line 2 "+quotedSketchLocation+"\n")
 
 	expectedSource := LoadAndInterpolate(t, filepath.Join("sketch_with_ifdef", "sketch.preprocessed.SAM.txt"), ctx)
-	require.Equal(t, expectedSource, strings.Replace(ctx.SketchSourceAfterArduinoPreprocessing, "\r\n", "\n", -1))
+	require.Equal(t, expectedSource, strings.Replace(preprocessedSketch, "\r\n", "\n", -1))
 }
 
 func TestPrototypesAdderSketchWithConst(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_const", "sketch_with_const.ino")
-	quotedSketchLocation := utils.QuoteCppPath(Abs(t, sketchLocation))
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:uno")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -564,7 +590,7 @@ func TestPrototypesAdderSketchWithConst(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -573,10 +599,11 @@ func TestPrototypesAdderSketchWithConst(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "#line 1 "+quotedSketchLocation+"\nvoid setup();\n#line 2 "+quotedSketchLocation+"\nvoid loop();\n#line 4 "+quotedSketchLocation+"\nconst __FlashStringHelper* test();\n#line 6 "+quotedSketchLocation+"\nconst int test3();\n#line 8 "+quotedSketchLocation+"\nvolatile __FlashStringHelper* test2();\n#line 10 "+quotedSketchLocation+"\nvolatile int test4();\n#line 1 "+quotedSketchLocation+"\n")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "#include <Arduino.h>\n#line 1 "+quotedSketchLocation+"\n")
+	require.Contains(t, preprocessedSketch, "#line 1 "+quotedSketchLocation+"\nvoid setup();\n#line 2 "+quotedSketchLocation+"\nvoid loop();\n#line 4 "+quotedSketchLocation+"\nconst __FlashStringHelper* test();\n#line 6 "+quotedSketchLocation+"\nconst int test3();\n#line 8 "+quotedSketchLocation+"\nvolatile __FlashStringHelper* test2();\n#line 10 "+quotedSketchLocation+"\nvolatile int test4();\n#line 1 "+quotedSketchLocation+"\n")
 }
 
 func TestPrototypesAdderSketchWithDosEol(t *testing.T) {
@@ -589,7 +616,7 @@ func TestPrototypesAdderSketchWithDosEol(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -598,13 +625,13 @@ func TestPrototypesAdderSketchWithDosEol(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 	// only requires no error as result
 }
 
 func TestPrototypesAdderSketchWithSubstringFunctionMember(t *testing.T) {
 	sketchLocation := paths.New("sketch_with_class_and_method_substring", "sketch_with_class_and_method_substring.ino")
-	quotedSketchLocation := utils.QuoteCppString(Abs(t, sketchLocation).String())
+	quotedSketchLocation := cpp.QuoteString(Abs(t, sketchLocation).String())
 
 	ctx := prepareBuilderTestContext(t, nil, sketchLocation, "arduino:avr:uno")
 	defer cleanUpBuilderTestContext(t, ctx)
@@ -615,7 +642,7 @@ func TestPrototypesAdderSketchWithSubstringFunctionMember(t *testing.T) {
 	commands := []types.Command{
 		&builder.ContainerSetupHardwareToolsLibsSketchAndProps{},
 		types.BareCommand(func(ctx *types.Context) error {
-			ctx.LineOffset, ctx.SketchSourceMerged, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
+			ctx.LineOffset, _err = bldr.PrepareSketchBuildPath(ctx.Sketch, ctx.SourceOverride, ctx.SketchBuildPath)
 			return _err
 		}),
 		&builder.ContainerFindIncludes{},
@@ -624,7 +651,8 @@ func TestPrototypesAdderSketchWithSubstringFunctionMember(t *testing.T) {
 		err := command.Run(ctx)
 		NoError(t, err)
 	}
-	NoError(t, builder.PreprocessSketchWithCtags(ctx))
+	NoError(t, builder.PreprocessSketch(ctx))
 
-	require.Contains(t, ctx.SketchSourceAfterArduinoPreprocessing, "class Foo {\nint blooper(int x) { return x+1; }\n};\n\nFoo foo;\n\n#line 7 "+quotedSketchLocation+"\nvoid setup();")
+	preprocessedSketch := loadPreprocessedSketch(t, ctx)
+	require.Contains(t, preprocessedSketch, "class Foo {\nint blooper(int x) { return x+1; }\n};\n\nFoo foo;\n\n#line 7 "+quotedSketchLocation+"\nvoid setup();")
 }
diff --git a/legacy/builder/test/try_build_of_problematic_sketch_test.go b/legacy/builder/test/try_build_of_problematic_sketch_test.go
index bb6457728ae..90f3633f2b6 100644
--- a/legacy/builder/test/try_build_of_problematic_sketch_test.go
+++ b/legacy/builder/test/try_build_of_problematic_sketch_test.go
@@ -20,6 +20,7 @@ import (
 	"path/filepath"
 	"testing"
 
+	"github.com/arduino/arduino-cli/arduino/builder/preprocessor"
 	"github.com/arduino/arduino-cli/legacy/builder"
 	"github.com/arduino/arduino-cli/legacy/builder/types"
 	paths "github.com/arduino/go-paths-helper"
@@ -202,7 +203,7 @@ func TestTryBuild042(t *testing.T) {
 }
 
 func makeDefaultContext() *types.Context {
-	builder.DebugPreprocessor = true
+	preprocessor.DebugPreprocessor = true
 	return &types.Context{
 		HardwareDirs:         paths.NewPathList(filepath.Join("..", "hardware"), "downloaded_hardware", "downloaded_board_manager_stuff"),
 		BuiltInToolsDirs:     paths.NewPathList("downloaded_tools"),
diff --git a/legacy/builder/test/utils_test.go b/legacy/builder/test/utils_test.go
index ec34a7bb670..a6a4dea8fb4 100644
--- a/legacy/builder/test/utils_test.go
+++ b/legacy/builder/test/utils_test.go
@@ -40,16 +40,3 @@ func TestPrintableCommand(t *testing.T) {
 	result := utils.PrintableCommand(parts)
 	require.Equal(t, correct, result)
 }
-
-func TestQuoteCppString(t *testing.T) {
-	cases := map[string]string{
-		`foo`:                                  `"foo"`,
-		`foo\bar`:                              `"foo\\bar"`,
-		`foo "is" quoted and \\bar"" escaped\`: `"foo \"is\" quoted and \\\\bar\"\" escaped\\"`,
-		// ASCII 0x20 - 0x7e, excluding `
-		` !"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\]^_abcdefghijklmnopqrstuvwxyz{|}~`: `" !\"#$%&'()*+,-./0123456789:;<=>?@ABCDEFGHIJKLMNOPQRSTUVWXYZ[\\]^_abcdefghijklmnopqrstuvwxyz{|}~"`,
-	}
-	for input, expected := range cases {
-		require.Equal(t, expected, utils.QuoteCppString(input))
-	}
-}
diff --git a/legacy/builder/types/context.go b/legacy/builder/types/context.go
index 2b5fd27b679..8bbd05f7308 100644
--- a/legacy/builder/types/context.go
+++ b/legacy/builder/types/context.go
@@ -94,21 +94,12 @@ type Context struct {
 	CoreObjectsFiles             paths.PathList
 	LibrariesBuildPath           *paths.Path
 	LibrariesObjectFiles         paths.PathList
-	PreprocPath                  *paths.Path
 	SketchObjectFiles            paths.PathList
 	IgnoreSketchFolderNameErrors bool
 
 	Sketch        *sketch.Sketch
 	WarningsLevel string
 
-	// Arduino sketch (.ino) to C++ (.cpp) conversion steps:
-	// 1. Concatenate *.ino files into a single merged source file -> SketchSourceMerged
-	SketchSourceMerged string
-	// 2. Run a pass of C++ preprocessor to remove macro definitions and ifdef-ed code -> SketchSourceAfterCppPreprocessing
-	SketchSourceAfterCppPreprocessing string
-	// 3. Do the Arduino preprocessing of the sketch (add missing prototypes) -> SketchSourceAfterArduinoPreprocessing
-	SketchSourceAfterArduinoPreprocessing string
-
 	// Libraries handling
 	LibrariesManager             *librariesmanager.LibrariesManager
 	LibrariesResolver            *librariesresolver.Cpp
diff --git a/legacy/builder/utils/utils.go b/legacy/builder/utils/utils.go
index 056940308fe..3efc8b73d6d 100644
--- a/legacy/builder/utils/utils.go
+++ b/legacy/builder/utils/utils.go
@@ -262,19 +262,6 @@ func LogIfVerbose(warn bool, msg string) types.Command {
 	return &loggerAction{onlyIfVerbose: true, warn: warn, msg: msg}
 }
 
-// Returns the given string as a quoted string for use with the C
-// preprocessor. This adds double quotes around it and escapes any
-// double quotes and backslashes in the string.
-func QuoteCppString(str string) string {
-	str = strings.Replace(str, "\\", "\\\\", -1)
-	str = strings.Replace(str, "\"", "\\\"", -1)
-	return "\"" + str + "\""
-}
-
-func QuoteCppPath(path *paths.Path) string {
-	return QuoteCppString(path.String())
-}
-
 // Normalizes an UTF8 byte slice
 // TODO: use it more often troughout all the project (maybe on logger interface?)
 func NormalizeUTF8(buf []byte) []byte {