cmd/go: disable warnings from cmd/cc when building for SWIG

Fixes #9065.

LGTM=rsc
R=rsc, misch
CC=golang-codereviews
https://golang.org/cl/171270043

diff --git a/src/cmd/go/build.go b/src/cmd/go/build.go
index 79a27116a1751e20d5c6ce5156ea2cfbc30a7794..1dd4314da659aaacb9fec30f2b738fd7a7e2bdeb 100644 (file)
--- a/src/cmd/go/build.go
+++ b/src/cmd/go/build.go
@@ -1826,7 +1826,15 @@ func (gcToolchain) ld(b *builder, p *Package, out string, allactions []*action,
 func (gcToolchain) cc(b *builder, p *Package, objdir, ofile, cfile string) error {
        inc := filepath.Join(goroot, "pkg", fmt.Sprintf("%s_%s", goos, goarch))
        cfile = mkAbs(p.Dir, cfile)
-       args := stringList(tool(archChar+"c"), "-F", "-V", "-w", "-trimpath", b.work, "-I", objdir, "-I", inc, "-o", ofile, buildCcflags, "-D", "GOOS_"+goos, "-D", "GOARCH_"+goarch, cfile)
+       warn := []string{"-w"}
+       if p.usesSwig() {
+               // When using SWIG, this compiler is only used to
+               // compile the C files generated by SWIG.
+               // We don't want warnings.
+               // See issue 9065 for details.
+               warn = nil
+       }
+       args := stringList(tool(archChar+"c"), "-F", "-V", warn, "-trimpath", b.work, "-I", objdir, "-I", inc, "-o", ofile, buildCcflags, "-D", "GOOS_"+goos, "-D", "GOARCH_"+goarch, cfile)
        return b.run(p.Dir, p.ImportPath, nil, args)
 }