Only trust function line number in main sketch file

Previously, function line numbers are extracted from any tag (in any file) so exctracted line is nonsense if the main sketch is empty/has lots of lines and lots of comments/etc

Fixes arduino#199

Author: facchinm

src/arduino.cc/builder/ctags/ctags_parser.go

@@ -53,13 +53,16 @@ var KNOWN_TAG_KINDS = map[string]bool{
 }
 
 type CTagsParser struct {
-	tags []*types.CTag
+	tags     []*types.CTag
+	mainFile string
 }
 
-func (p *CTagsParser) Parse(ctagsOutput string) []*types.CTag {
+func (p *CTagsParser) Parse(ctagsOutput string, mainFile string) []*types.CTag {
 	rows := strings.Split(ctagsOutput, "\n")
 	rows = removeEmpty(rows)
 
+	p.mainFile = mainFile
+
 	for _, row := range rows {
 		p.tags = append(p.tags, parseTag(row))
 	}

src/arduino.cc/builder/ctags/ctags_to_prototypes.go

@@ -48,10 +48,12 @@ func (p *CTagsParser) findLineWhereToInsertPrototypes() int {
 		} else {
 			return firstFunctionPointerAsArgument
 		}
-	} else if firstFunctionLine == -1 {
+	} else if firstFunctionLine != -1 {
+		return firstFunctionLine
+	} else if firstFunctionPointerAsArgument != -1 {
 		return firstFunctionPointerAsArgument
 	} else {
-		return firstFunctionLine
+		return 0
 	}
 }
 
@@ -86,7 +88,7 @@ func (p *CTagsParser) collectFunctionNames() []string {
 
 func (p *CTagsParser) firstFunctionAtLine() int {
 	for _, tag := range p.tags {
-		if !tagIsUnknown(tag) && isHandled(tag) && tag.Kind == KIND_FUNCTION {
+		if !tagIsUnknown(tag) && isHandled(tag) && tag.Kind == KIND_FUNCTION && tag.Filename == p.mainFile {
 			return tag.Line
 		}
 	}

src/arduino.cc/builder/ctags_runner.go

@@ -74,7 +74,8 @@ func (s *CTagsRunner) Run(ctx *types.Context) error {
 	ctx.CTagsOutput = string(sourceBytes)
 
 	parser := &ctags.CTagsParser{}
-	ctx.CTagsOfPreprocessedSource = parser.Parse(ctx.CTagsOutput)
+	ctx.CTagsOfPreprocessedSource = parser.Parse(ctx.CTagsOutput, ctx.Sketch.MainFile.Name)
+
 	protos, line := parser.GeneratePrototypes()
 	if line != -1 {
 		ctx.PrototypesLineWhereToInsert = line