cmd/cgo: fix C.CString for strings containing null term...

cmd/cgo: fix C.CString for strings containing null terminators under gccgo

Previously we used strndup(3) to implement C.CString for gccgo. This
is wrong because strndup assumes the string to be null terminated,
and stops at the first null terminator. Instead, use malloc
and memmove to create a copy of the string, as we do in the
gc implementation.

[iant, 2014-04-27 05:16:21]

LGTM

[iant, 2014-04-27 05:16:41]

*** Submitted as https://code.google.com/p/go/source/detail?r=6cf757123ad4 ***

cmd/cgo: fix C.CString for strings containing null terminators under gccgo

Previously we used strndup(3) to implement C.CString for gccgo. This
is wrong because strndup assumes the string to be null terminated,
and stops at the first null terminator. Instead, use malloc
and memmove to create a copy of the string, as we do in the
gc implementation.

LGTM=iant
R=iant
CC=golang-codereviews
https://codereview.appspot.com/96790047

Committer: Ian Lance Taylor <iant@golang.org>

[ioe, 2014-04-27 15:17:07]

I agree that this is a nice security stop gap, but 
wouldn't a behavior similar to syscall.BytePtrFromString() be more useful here?

That way the caller has a chance to find the now existing issue (zero in middle
of a zero terminated string) via testing.

On Sunday, April 27, 2014 7:16:41 AM UTC+2, Ian Lance Taylor wrote:
> *** Submitted as
> 
> https://code.google.com/p/go/source/detail?r=6cf757123ad4 ***
> 
> 
> 
> cmd/cgo: fix C.CString for strings containing null terminators under
> 
> gccgo

[iant, 2014-04-27 16:23:54]

On Apr 27, 2014 9:17 AM, <nightlyone@googlemail.com> wrote:
>
> I agree that this is a nice security stop gap, but
> wouldn't a behavior similar to syscall.BytePtrFromString() be more useful
here?
>
> That way the caller has a chance to find the now existing issue (zero in
middle of a zero terminated string) via testing.

Unlike the syscall package, we don't know the API here.  The length may be
passed separately.  In any case, this CL just makes gccgo act like gc.

Ian

> On Sunday, April 27, 2014 7:16:41 AM UTC+2, Ian Lance Taylor wrote:
> > *** Submitted as
> >
> > https://code.google.com/p/go/source/detail?r=6cf757123ad4 ***
> >
> >
> >
> > cmd/cgo: fix C.CString for strings containing null terminators under
> >
> > gccgo