cmd/go: Add support for including C++ files in packages

* Add a CXXFiles field to Package, which includes .cc, .cpp and .cxx  files.
* CXXFiles are compiled using g++, which can be overridden using the CXX environment variable.
* Include .hh, .hpp and .hxx files in HFiles.
* Add support for CPPFLAGS (used for both C and C++) and CXXFLAGS (used only for C++) in cgo directive.
* Changed pkg-config cgo directive to modify CPPFLAGS rather than CFLAGS, so both C and C++ files get any flag returned by pkg-config --cflags.

Fixes #1476.

R=iant, r
CC=bradfitz, gobot, golang-dev, iant, minux.ma, remyoudompheng, seb.binet
https://golang.org/cl/8248043

src/cmd/cgo/doc.go

@@ -24,7 +24,7 @@ the C parts of the package.  For example:
 	// #include <errno.h>
 	import "C"
 
-CFLAGS and LDFLAGS may be defined with pseudo #cgo directives
+CPPFLAGS, CFLAGS, CXXFLAGS and LDFLAGS may be defined with pseudo #cgo directives
 within these comments to tweak the behavior of gcc.  Values defined
 in multiple directives are concatenated together.  Options prefixed
 by $GOOS, $GOARCH, or $GOOS/$GOARCH are only defined in matching
@@ -36,7 +36,7 @@ systems.  For example:
 	// #include <png.h>
 	import "C"
 
-Alternatively, CFLAGS and LDFLAGS may be obtained via the pkg-config
+Alternatively, CPPFLAGS and LDFLAGS may be obtained via the pkg-config
 tool using a '#cgo pkg-config:' directive followed by the package names.
 For example:
 
@@ -44,7 +44,7 @@ For example:
 	// #include <png.h>
 	import "C"
 
-The CGO_CFLAGS and CGO_LDFLAGS environment variables are added
+The CGO_CPPFLAGS, CGO_CFLAGS, CGO_CXXFLAGS and CGO_LDFLAGS environment variables are added
 to the flags derived from these directives.  Package-specific flags should
 be set using the directives, not the environment variables, so that builds
 work in unmodified environments.

src/cmd/go/doc.go

@@ -318,14 +318,17 @@ which calls strings.Join. The struct being passed to the template is:
         CgoFiles []string       // .go sources files that import "C"
         IgnoredGoFiles []string // .go sources ignored due to build constraints
         CFiles   []string       // .c source files
-        HFiles   []string       // .h source files
+        CXXFiles []string       // .cc, .cxx and .cpp source files
+        HFiles   []string       // .h, .hh, .hpp and .hxx source files
         SFiles   []string       // .s source files
         SysoFiles []string      // .syso object files to add to archive
         SwigFiles []string      // .swig files
         SwigCXXFiles []string   // .swigcxx files
 
         // Cgo directives
+        CgoCPPFLAGS  []string // cgo: flags for C preprocessor
         CgoCFLAGS    []string // cgo: flags for C compiler
+        CgoCXXFLAGS  []string // cgo: flags for C++ compiler
         CgoLDFLAGS   []string // cgo: flags for linker
         CgoPkgConfig []string // cgo: pkg-config names
 

src/cmd/go/list.go

@@ -46,14 +46,17 @@ which calls strings.Join. The struct being passed to the template is:
         CgoFiles []string       // .go sources files that import "C"
         IgnoredGoFiles []string // .go sources ignored due to build constraints
         CFiles   []string       // .c source files
-        HFiles   []string       // .h source files
+        CXXFiles []string       // .cc, .cxx and .cpp source files
+        HFiles   []string       // .h, .hh, .hpp and .hxx source files
         SFiles   []string       // .s source files
         SysoFiles []string      // .syso object files to add to archive
         SwigFiles []string      // .swig files
         SwigCXXFiles []string   // .swigcxx files
 
         // Cgo directives
+        CgoCPPFLAGS  []string // cgo: flags for C preprocessor
         CgoCFLAGS    []string // cgo: flags for C compiler
+        CgoCXXFLAGS  []string // cgo: flags for C++ compiler
         CgoLDFLAGS   []string // cgo: flags for linker
         CgoPkgConfig []string // cgo: pkg-config names
 

src/cmd/go/pkg.go

@@ -40,14 +40,17 @@ type Package struct {
 	CgoFiles       []string `json:",omitempty"` // .go sources files that import "C"
 	IgnoredGoFiles []string `json:",omitempty"` // .go sources ignored due to build constraints
 	CFiles         []string `json:",omitempty"` // .c source files
-	HFiles         []string `json:",omitempty"` // .h source files
+	CXXFiles       []string `json:",omitempty"` // .cc, .cpp and .cxx source files
+	HFiles         []string `json:",omitempty"` // .h, .hh, .hpp and .hxx source files
 	SFiles         []string `json:",omitempty"` // .s source files
 	SysoFiles      []string `json:",omitempty"` // .syso system object files added to package
 	SwigFiles      []string `json:",omitempty"` // .swig files
 	SwigCXXFiles   []string `json:",omitempty"` // .swigcxx files
 
 	// Cgo directives
+	CgoCPPFLAGS  []string `json:",omitempty"` // cgo: flags for C preprocessor
 	CgoCFLAGS    []string `json:",omitempty"` // cgo: flags for C compiler
+	CgoCXXFLAGS  []string `json:",omitempty"` // cgo: flags for C++ compiler
 	CgoLDFLAGS   []string `json:",omitempty"` // cgo: flags for linker
 	CgoPkgConfig []string `json:",omitempty"` // cgo: pkg-config names
 
@@ -98,12 +101,15 @@ func (p *Package) copyBuild(pp *build.Package) {
 	p.CgoFiles = pp.CgoFiles
 	p.IgnoredGoFiles = pp.IgnoredGoFiles
 	p.CFiles = pp.CFiles
+	p.CXXFiles = pp.CXXFiles
 	p.HFiles = pp.HFiles
 	p.SFiles = pp.SFiles
 	p.SysoFiles = pp.SysoFiles
 	p.SwigFiles = pp.SwigFiles
 	p.SwigCXXFiles = pp.SwigCXXFiles
+	p.CgoCPPFLAGS = pp.CgoCPPFLAGS
 	p.CgoCFLAGS = pp.CgoCFLAGS
+	p.CgoCXXFLAGS = pp.CgoCXXFLAGS
 	p.CgoLDFLAGS = pp.CgoLDFLAGS
 	p.CgoPkgConfig = pp.CgoPkgConfig
 	p.Imports = pp.Imports
@@ -389,6 +395,7 @@ func (p *Package) load(stk *importStack, bp *build.Package, err error) *Package
 		p.CgoFiles,
 		p.IgnoredGoFiles,
 		p.CFiles,
+		p.CXXFiles,
 		p.HFiles,
 		p.SFiles,
 		p.SysoFiles,
@@ -481,6 +488,11 @@ func (p *Package) usesSwig() bool {
 	return len(p.SwigFiles) > 0 || len(p.SwigCXXFiles) > 0
 }
 
+// usesCgo returns whether the package needs to run cgo
+func (p *Package) usesCgo() bool {
+	return len(p.CgoFiles) > 0
+}
+
 // swigSoname returns the name of the shared library we create for a
 // SWIG input file.
 func (p *Package) swigSoname(file string) string {
@@ -611,7 +623,7 @@ func isStale(p *Package, topRoot map[string]bool) bool {
 		return false
 	}
 
-	srcs := stringList(p.GoFiles, p.CFiles, p.HFiles, p.SFiles, p.CgoFiles, p.SysoFiles)
+	srcs := stringList(p.GoFiles, p.CFiles, p.CXXFiles, p.HFiles, p.SFiles, p.CgoFiles, p.SysoFiles)
 	for _, src := range srcs {
 		if olderThan(filepath.Join(p.Dir, src)) {
 			return true

src/cmd/godoc/index.go

@@ -657,10 +657,16 @@ func (x *Indexer) addFile(filename string, goFile bool) (file *token.File, ast *
 var whitelisted = map[string]bool{
 	".bash":        true,
 	".c":           true,
+	".cc":          true,
+	".cpp":         true,
+	".cxx":         true,
 	".css":         true,
 	".go":          true,
 	".goc":         true,
 	".h":           true,
+	".hh":          true,
+	".hpp":         true,
+	".hxx":         true,
 	".html":        true,
 	".js":          true,
 	".out":         true,

src/pkg/go/build/build.go

@@ -353,16 +353,19 @@ type Package struct {
 	CgoFiles       []string // .go source files that import "C"
 	IgnoredGoFiles []string // .go source files ignored for this build
 	CFiles         []string // .c source files
-	HFiles         []string // .h source files
+	CXXFiles       []string // .cc, .cpp and .cxx source files
+	HFiles         []string // .h, .hh, .hpp and .hxx source files
 	SFiles         []string // .s source files
 	SysoFiles      []string // .syso system object files to add to archive
 	SwigFiles      []string // .swig files
 	SwigCXXFiles   []string // .swigcxx files
 
 	// Cgo directives
-	CgoPkgConfig []string // Cgo pkg-config directives
+	CgoCPPFLAGS  []string // Cgo CPPFLAGS directives
 	CgoCFLAGS    []string // Cgo CFLAGS directives
+	CgoCXXFLAGS  []string // Cgo CXXFLAGS directives
 	CgoLDFLAGS   []string // Cgo LDFLAGS directives
+	CgoPkgConfig []string // Cgo pkg-config directives
 
 	// Dependency information
 	Imports   []string                    // imports from GoFiles, CgoFiles
@@ -600,7 +603,7 @@ Found:
 		}
 
 		switch ext {
-		case ".go", ".c", ".s", ".h", ".S", ".swig", ".swigcxx":
+		case ".go", ".c", ".cc", ".cxx", ".cpp", ".s", ".h", ".hh", ".hpp", ".hxx", ".S", ".swig", ".swigcxx":
 			// tentatively okay - read to make sure
 		case ".syso":
 			// binary objects to add to package archive
@@ -643,7 +646,10 @@ Found:
 		case ".c":
 			p.CFiles = append(p.CFiles, name)
 			continue
-		case ".h":
+		case ".cc", ".cpp", ".cxx":
+			p.CXXFiles = append(p.CXXFiles, name)
+			continue
+		case ".h", ".hh", ".hpp", ".hxx":
 			p.HFiles = append(p.HFiles, name)
 			continue
 		case ".s":
@@ -851,8 +857,8 @@ func (ctxt *Context) shouldBuild(content []byte) bool {
 }
 
 // saveCgo saves the information from the #cgo lines in the import "C" comment.
-// These lines set CFLAGS and LDFLAGS and pkg-config directives that affect
-// the way cgo's C code is built.
+// These lines set CPPCFLAGS, CFLAGS, CXXFLAGS and LDFLAGS and pkg-config directives
+// that affect the way cgo's C code is built.
 //
 // TODO(rsc): This duplicates code in cgo.
 // Once the dust settles, remove this code from cgo.
@@ -910,6 +916,10 @@ func (ctxt *Context) saveCgo(filename string, di *Package, cg *ast.CommentGroup)
 		switch verb {
 		case "CFLAGS":
 			di.CgoCFLAGS = append(di.CgoCFLAGS, args...)
+		case "CPPFLAGS":
+			di.CgoCPPFLAGS = append(di.CgoCPPFLAGS, args...)
+		case "CXXFLAGS":
+			di.CgoCXXFLAGS = append(di.CgoCXXFLAGS, args...)
 		case "LDFLAGS":
 			di.CgoLDFLAGS = append(di.CgoLDFLAGS, args...)
 		case "pkg-config":