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cmd/cgo: fix Xcode 5 incompatibility for #defined expressions

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Ensure that clang always exits with a non-zero status by
giving it something that it always warns about (the statement "1;").

Fixes #6128.

R=golang-dev, iant, minux.ma
CC=golang-dev
https://golang.org/cl/14702043
This commit is contained in:
Russ Cox 2013-10-15 14:34:46 -04:00
parent 74f639176d
commit 043ace1213
2 changed files with 33 additions and 0 deletions
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13
src/cmd/cgo/gcc.go
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@ -304,6 +304,19 @@ func (p *Package) guessKinds(f *File) []*Name {
b.WriteString(builtinProlog)
b.WriteString(f.Preamble)
b.WriteString("void __cgo__f__(void) {\n")
// For a #defined expression, clang silences the warning about "unused expression".
// http://llvm.org/viewvc/llvm-project?view=revision&revision=172696
// Silencing the warning is not a big deal, because our default assumption is that
// (in the absence of other evidence) names are expressions.
// However, if all the C names we are investigating are #defined expressions,
// clang will print no warnings at all and then exit successfully.
// We want clang to print warnings, so seed the code with a function
// that is guaranteed to provoke a warning (that we will ignore).
// This way, if clang becomes even more broken, we'll find out.
// See golang.org/issue/6128.
fmt.Fprintf(&b, "1;\n")
b.WriteString("#line 1 \"cgo-test\"\n")
for i, n := range toSniff {
fmt.Fprintf(&b, "%s; /* #%d */\nenum { _cgo_enum_%d = %s }; /* #%d */\n", n.C, i, i, n.C, i)