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cmd/go: if there are C++ sources, use g++ as default external linker

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This will bring in the C++ standard library without requiring
any special #cgo LDFLAGS options.

When using gccgo, just add -lstdc++ to link line; this should
do no harm if it is not needed.

No tests, since we don't want to assume a C++ compiler.

Update #5629

R=golang-dev, minux.ma, rsc
CC=golang-dev
https://golang.org/cl/13394045
This commit is contained in:
Ian Lance Taylor 2013-09-09 12:50:49 -07:00
parent 7d734d9252
commit f0ff63ea64
1 changed files with 51 additions and 1 deletions
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52
src/cmd/go/build.go
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@ -1553,6 +1553,7 @@ func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action,
importArgs := b.includeArgs("-L", allactions)
swigDirs := make(map[string]bool)
swigArg := []string{}
cxx := false
for _, a := range allactions {
if a.p != nil && a.p.usesSwig() {
sd := a.p.swigDir(&buildContext)
@ -1564,8 +1565,50 @@ func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action,
}
swigDirs[sd] = true
}
if a.p != nil && len(a.p.CXXFiles) > 0 {
cxx = true
}
}
return b.run(".", p.ImportPath, nil, tool(archChar+"l"), "-o", out, importArgs, swigArg, buildLdflags, mainpkg)
ldflags := buildLdflags
if cxx {
// The program includes C++ code. If the user has not
// specified the -extld option, then default to
// linking with the compiler named by the CXX
// environment variable, or g++ if CXX is not set.
extld := false
for _, f := range ldflags {
if f == "-extld" || strings.HasPrefix(f, "-extld=") {
extld = true
break
}
}
if !extld {
compiler := strings.Fields(os.Getenv("CXX"))
if len(compiler) == 0 {
compiler = []string{"g++"}
}
ldflags = append(ldflags, "-extld="+compiler[0])
if len(compiler) > 1 {
extldflags := false
add := strings.Join(compiler[1:], " ")
for i, f := range ldflags {
if f == "-extldflags" && i+1 < len(ldflags) {
ldflags[i+1] = add + " " + ldflags[i+1]
extldflags = true
break
} else if strings.HasPrefix(f, "-extldflags=") {
ldflags[i] = "-extldflags=" + add + " " + ldflags[i][len("-extldflags="):]
extldflags = true
break
}
}
if !extldflags {
ldflags = append(ldflags, "-extldflags="+add)
}
}
}
}
return b.run(".", p.ImportPath, nil, tool(archChar+"l"), "-o", out, importArgs, swigArg, ldflags, mainpkg)
}
func (gcToolchain) cc(b *builder, p *Package, objdir, ofile, cfile string) error {
@ -1641,6 +1684,7 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
ldflags := b.gccArchArgs()
cgoldflags := []string{}
usesCgo := false
cxx := false
for _, a := range allactions {
if a.p != nil {
if !a.p.Standard {
@ -1660,6 +1704,9 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
}
usesCgo = true
}
if len(a.p.CXXFiles) > 0 {
cxx = true
}
}
}
for _, afile := range afiles {
@ -1672,6 +1719,9 @@ func (tools gccgoToolchain) ld(b *builder, p *Package, out string, allactions []
if usesCgo && goos == "linux" {
ldflags = append(ldflags, "-Wl,-E")
}
if cxx {
ldflags = append(ldflags, "-lstdc++")
}
return b.run(".", p.ImportPath, nil, "gccgo", "-o", out, ofiles, "-Wl,-(", ldflags, "-Wl,-)", buildGccgoflags)
}