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cgo: use packed struct to fix Windows behavior

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R=golang-dev, mattn.jp, jcowgar, iant
CC=golang-dev
https://golang.org/cl/4535080
This commit is contained in:
Russ Cox 2011-05-18 14:08:12 -04:00
parent 82ddf97094
commit 975ba88e0e
1 changed files with 9 additions and 3 deletions
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12
src/cmd/cgo/out.go
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@ -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)
}