From 975ba88e0e6c0de73d9c80de67013256be75b49e Mon Sep 17 00:00:00 2001 From: Russ Cox Date: Wed, 18 May 2011 14:08:12 -0400 Subject: [PATCH] cgo: use packed struct to fix Windows behavior R=golang-dev, mattn.jp, jcowgar, iant CC=golang-dev https://golang.org/cl/4535080 --- src/cmd/cgo/out.go | 12 +++++++++--- 1 file changed, 9 insertions(+), 3 deletions(-) diff --git a/src/cmd/cgo/out.go b/src/cmd/cgo/out.go index bc031cc58c..2ce4e97528 100644 --- a/src/cmd/cgo/out.go +++ b/src/cmd/cgo/out.go @@ -331,7 +331,11 @@ func (p *Package) writeOutputFunc(fgcc *os.File, n *Name) { fmt.Fprintf(fgcc, "\tint e;\n") // assuming 32 bit (see comment above structType) fmt.Fprintf(fgcc, "\terrno = 0;\n") } - fmt.Fprintf(fgcc, "\t%s *a = v;\n", ctype) + // We're trying to write a gcc struct that matches 6c/8c/5c's layout. + // Use packed attribute to force no padding in this struct in case + // gcc has different packing requirements. For example, + // on 386 Windows, gcc wants to 8-align int64s, but 8c does not. + fmt.Fprintf(fgcc, "\t%s __attribute__((__packed__)) *a = v;\n", ctype) fmt.Fprintf(fgcc, "\t") if t := n.FuncType.Result; t != nil { fmt.Fprintf(fgcc, "a->r = ") @@ -370,7 +374,9 @@ func (p *Package) writeExports(fgo2, fc, fm *os.File) { fn := exp.Func // Construct a gcc struct matching the 6c argument and - // result frame. + // result frame. The gcc struct will be compiled with + // __attribute__((packed)) so all padding must be accounted + // for explicitly. ctype := "struct {\n" off := int64(0) npad := 0 @@ -458,7 +464,7 @@ func (p *Package) writeExports(fgo2, fc, fm *os.File) { fmt.Fprintf(fgcc, "extern _cgoexp%s_%s(void *, int);\n", cPrefix, exp.ExpName) fmt.Fprintf(fgcc, "\n%s\n", s) fmt.Fprintf(fgcc, "{\n") - fmt.Fprintf(fgcc, "\t%s a;\n", ctype) + fmt.Fprintf(fgcc, "\t%s __attribute__((packed)) a;\n", ctype) if gccResult != "void" && (len(fntype.Results.List) > 1 || len(fntype.Results.List[0].Names) > 1) { fmt.Fprintf(fgcc, "\t%s r;\n", gccResult) }