code review 13413047: cmd/cgo: replace C.malloc with our own wrapper

cmd/cgo: replace C.malloc with our own wrapper

This allows us to make two changes:

1. Force the argument type to be size_t, even on broken
   systems that declare malloc to take a ulong.

2. Call runtime.throw if malloc fails.
   (That is, the program crashes; it does not panic.)

Fixes issue 3403.
Fixes issue 5926.

[rsc, 2013-09-11 13:13:07]

Hello golang-dev@googlegroups.com,

I'd like you to review this change to
https://code.google.com/p/go/

[iant, 2013-09-11 14:07:37]

I don't see any test of this--nothing in misc/cgo/test seems to call malloc
directly.

https://codereview.appspot.com/13413047/diff/5001/src/cmd/cgo/out.go
File src/cmd/cgo/out.go (right):

https://codereview.appspot.com/13413047/diff/5001/src/cmd/cgo/out.go#newcode1179
src/cmd/cgo/out.go:1179: ·_Cfunc__CMalloc(uintptr n, int8 *p)
You need to add this to cPrologGccgo as well.

extern void runtime_throw(const char *):
void *Cmalloc(size_t n) {
        void *p = malloc(n);
        if(p == NULL)
                runtime_throw("runtime: C malloc failed");
        return p;
}

[rsc, 2013-09-11 14:48:01]

On Wed, Sep 11, 2013 at 10:07 AM, <iant@golang.org> wrote:

> I don't see any test of this--nothing in misc/cgo/test seems to call
> malloc directly.
>

I tested it by hand. We're not set up for cgo tests that crash the program.


https://codereview.appspot.**com/13413047/diff/5001/src/**
>
cmd/cgo/out.go#newcode1179<https://codereview.appspot.com/13413047/diff/5001/src/cmd/cgo/out.go#newcode1179>
> src/cmd/cgo/out.go:1179: ·_Cfunc__CMalloc(uintptr n, int8 *p)
> You need to add this to cPrologGccgo as well.
>

Done.

[rsc, 2013-09-11 14:48:28]

Oh, and for what it's worth there are calls to C.malloc in os/user.

Russ

[iant, 2013-09-11 15:29:02]

LGTM

I didn't expect a crash test, just something that called malloc to make sure it
did something reasonable.  I forgot about os/user.

[rsc, 2013-09-11 15:30:12]

*** Submitted as https://code.google.com/p/go/source/detail?r=46fd4ef6c0de ***

cmd/cgo: replace C.malloc with our own wrapper

This allows us to make two changes:

1. Force the argument type to be size_t, even on broken
   systems that declare malloc to take a ulong.

2. Call runtime.throw if malloc fails.
   (That is, the program crashes; it does not panic.)

Fixes issue 3403.
Fixes issue 5926.

R=golang-dev, iant
CC=golang-dev
https://codereview.appspot.com/13413047