From 09c6d13ac248eefd1d47e20457125ab5ac8b3246 Mon Sep 17 00:00:00 2001 From: Ian Lance Taylor Date: Sat, 26 Sep 2015 18:37:06 -0700 Subject: [PATCH] cmd/cgo: only declare real function in gccgo exported header file When exporting a function using gccgo, we generate two functions: a Go function with a leading Cgoexp_ prefix, and a C function that calls the Go function. The Go function has a name that can not be represented in C, so the C code needs a declaration with an __asm__ qualifier giving the name of the Go function. Before this CL we put that declaration in the exported header file. Because code would sometimes #include "_cgo_export.h", we added a macro definition for the C function giving it the name of the declaration. We then added a macro undefine in the actual C code, so that we could declare the C function we wanted. This rounadabout process worked OK until we started exporting the header file for use with -buildmode=c-archive and c-shared. Doing that caused the code to see the define and thus call the Go function rather than the C function. That often works fine, but the C function calls _cgo_wait_runtime_init_done before calling the Go function, and that sometimes matters. This didn't show up in tests because we don't test using gccgo. That is something we should fix, but not now. Fix that by simplifying the code to declare the C function in the header file as one would expect, and move the __asm__ declaration to the C code. Change-Id: I33547e028152ff98e332630994b4f33285feec32 Reviewed-on: https://go-review.googlesource.com/15043 Reviewed-by: Minux Ma --- src/cmd/cgo/out.go | 16 ++++------------ 1 file changed, 4 insertions(+), 12 deletions(-) diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go index aaa105d6fd..b69f410d15 100644 --- a/src/cmd/cgo/out.go +++ b/src/cmd/cgo/out.go @@ -933,23 +933,15 @@ func (p *Package) writeGccgoExports(fgo2, fm, fgcc, fgcch io.Writer) { fmt.Fprintf(fgcch, "\n%s", exp.Doc) } + fmt.Fprintf(fgcch, "extern %s %s %s;\n", cRet, exp.ExpName, cParams) + // We need to use a name that will be exported by the // Go code; otherwise gccgo will make it static and we // will not be able to link against it from the C // code. goName := "Cgoexp_" + exp.ExpName - fmt.Fprintf(fgcch, `extern %s %s %s __asm__("%s.%s");`, cRet, goName, cParams, gccgoSymbolPrefix, goName) - fmt.Fprint(fgcch, "\n") - - // Use a #define so that the C code that includes - // cgo_export.h will be able to refer to the Go - // function using the expected name. - fmt.Fprintf(fgcch, "#define %s %s\n", exp.ExpName, goName) - - // Use a #undef in _cgo_export.c so that we ignore the - // #define from cgo_export.h, since here we are - // defining the real function. - fmt.Fprintf(fgcc, "#undef %s\n", exp.ExpName) + fmt.Fprintf(fgcc, `extern %s %s %s __asm__("%s.%s");`, cRet, goName, cParams, gccgoSymbolPrefix, goName) + fmt.Fprint(fgcc, "\n") fmt.Fprint(fgcc, "\n") fmt.Fprintf(fgcc, "%s %s %s {\n", cRet, exp.ExpName, cParams) -- 2.48.1