Add LDFLAGS to library properties and use to link dynamic libs

Since ld uses absolute paths in certain conditions, adopt a different strategy for dynamic libraries. "compiler.c.elf.extra_flags" must be defined and used in "recipe.c.combine" (at least)

Author: facchinm

Diff for: src/arduino.cc/builder/constants/constants.go

@@ -48,6 +48,7 @@ const BUILD_PROPERTIES_BUILD_SYSTEM_PATH = "build.system.path"
 const BUILD_PROPERTIES_BUILD_VARIANT = "build.variant"
 const BUILD_PROPERTIES_BUILD_VARIANT_PATH = "build.variant.path"
 const BUILD_PROPERTIES_COMPILER_C_ELF_FLAGS = "compiler.c.elf.flags"
+const BUILD_PROPERTIES_COMPILER_C_ELF_EXTRAFLAGS = "compiler.c.elf.extra_flags"
 const BUILD_PROPERTIES_COMPILER_CPP_FLAGS = "compiler.cpp.flags"
 const BUILD_PROPERTIES_COMPILER_PATH = "compiler.path"
 const BUILD_PROPERTIES_COMPILER_WARNING_FLAGS = "compiler.warning_flags"
@@ -138,6 +139,7 @@ const LIBRARY_MAINTAINER = "maintainer"
 const LIBRARY_NAME = "name"
 const LIBRARY_PARAGRAPH = "paragraph"
 const LIBRARY_PRECOMPILED = "precompiled"
+const LIBRARY_LDFLAGS = "ldflags"
 const LIBRARY_PROPERTIES = "library.properties"
 const LIBRARY_SENTENCE = "sentence"
 const LIBRARY_URL = "url"

Diff for: src/arduino.cc/builder/libraries_loader.go

@@ -194,6 +194,7 @@ func makeNewLibrary(libraryFolder string, debugLevel int, logger i18n.Logger) (*
 	library.IsLegacy = false
 	library.DotALinkage = strings.TrimSpace(libProperties[constants.LIBRARY_DOT_A_LINKAGE]) == "true"
 	library.Precompiled = strings.TrimSpace(libProperties[constants.LIBRARY_PRECOMPILED]) == "true"
+	library.LDflags = strings.TrimSpace(libProperties[constants.LIBRARY_LDFLAGS])
 	library.Properties = libProperties
 
 	return library, nil

Diff for: src/arduino.cc/builder/phases/libraries_builder.go

@@ -41,7 +41,8 @@ import (
 	"arduino.cc/properties"
 )
 
-var PRECOMPILED_LIBRARIES_VALID_EXTENSIONS = map[string]bool{".a": true, ".so": true}
+var PRECOMPILED_LIBRARIES_VALID_EXTENSIONS_STATIC = map[string]bool{".a": true}
+var PRECOMPILED_LIBRARIES_VALID_EXTENSIONS_DYNAMIC = map[string]bool{".so": true}
 
 type LibrariesBuilder struct{}
 
@@ -67,6 +68,34 @@ func (s *LibrariesBuilder) Run(ctx *types.Context) error {
 
 	ctx.LibrariesObjectFiles = objectFiles
 
+	// Search for precompiled libraries
+	fixLDFLAGforPrecompiledLibraries(ctx, libraries)
+
+	return nil
+}
+
+func fixLDFLAGforPrecompiledLibraries(ctx *types.Context, libraries []*types.Library) error {
+
+	for _, library := range libraries {
+		if library.Precompiled {
+			// add library src path to compiler.c.elf.extra_flags
+			// use library.Name as lib name and srcPath/{mcpu} as location
+			mcu := ctx.BuildProperties[constants.BUILD_PROPERTIES_BUILD_MCU]
+			path := filepath.Join(library.SrcFolder, mcu)
+			// find all library names in the folder and prepend -l
+			filePaths := []string{}
+			libs_cmd := library.LDflags + " "
+			extensions := func(ext string) bool { return PRECOMPILED_LIBRARIES_VALID_EXTENSIONS_DYNAMIC[ext] }
+			utils.FindFilesInFolder(&filePaths, path, extensions, true)
+			for _, lib := range filePaths {
+				name := strings.TrimSuffix(filepath.Base(lib), filepath.Ext(lib))
+				// strip "lib" first occurrence
+				name = strings.Replace(name, "lib", "", 1)
+				libs_cmd += "-l" + name + " "
+			}
+			ctx.BuildProperties[constants.BUILD_PROPERTIES_COMPILER_C_ELF_EXTRAFLAGS] += "\"-L" + path + "\" " + libs_cmd
+		}
+	}
 	return nil
 }
 
@@ -99,7 +128,7 @@ func compileLibrary(library *types.Library, buildPath string, buildProperties pr
 
 	if library.Precompiled {
 		// search for files with PRECOMPILED_LIBRARIES_VALID_EXTENSIONS
-		extensions := func(ext string) bool { return PRECOMPILED_LIBRARIES_VALID_EXTENSIONS[ext] }
+		extensions := func(ext string) bool { return PRECOMPILED_LIBRARIES_VALID_EXTENSIONS_STATIC[ext] }
 
 		filePaths := []string{}
 		mcu := buildProperties[constants.BUILD_PROPERTIES_BUILD_MCU]

Diff for: src/arduino.cc/builder/types/types.go

@@ -172,6 +172,7 @@ type Library struct {
 	Archs         []string
 	DotALinkage   bool
 	Precompiled   bool
+	LDflags       string
 	IsLegacy      bool
 	Version       string
 	Author        string