code review 130720043: cmd/gc: disallow pointer constants

cmd/gc: disallow pointer constants

Fixes issue 7760.

[mdempsky, 2014-08-15 07:56:03]

Hello iant@golang.org (cc: golang-codereviews@googlegroups.com),

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

[iant, 2014-08-15 13:14:48]

unsafe.Pointer is not the only invalid constant type, so it seems odd to check
for it particularly.  I admit that I can't think of a way that any other type
could get in there, but I think it would be more robust to check that the type
conversion is to a type that could be a constant, rather than rule out a
specific case.

All constants must have integer, float, complex, bool, or string type.

[remyoudompheng, 2014-08-15 15:13:15]

On 2014/08/15 13:14:48, iant wrote:
> unsafe.Pointer is not the only invalid constant type, so it seems odd to check
> for it particularly.  I admit that I can't think of a way that any other type
> could get in there, but I think it would be more robust to check that the type
> conversion is to a type that could be a constant, rather than rule out a
> specific case.
> 
> All constants must have integer, float, complex, bool, or string type.

The other possible type is byteslice (conversion from string), where is it
handled ?

[mdempsky, 2014-08-15 16:10:49]

On 2014/08/15 13:14:48, iant wrote:
> unsafe.Pointer is not the only invalid constant type, so it seems odd to check
> for it particularly.  I admit that I can't think of a way that any other type
> could get in there, but I think it would be more robust to check that the type
> conversion is to a type that could be a constant, rather than rule out a
> specific case.

Good point, done.  PTAL

On 2014/08/15 15:13:15, remyoudompheng wrote:
> The other possible type is byteslice (conversion from string), where is it
> handled ?

Conversion from string to []byte is represented as an OSTRARRAYBYTE node and
rejected already, but I added in some extra test cases for this anyway since it
seems worth checking.

[iant, 2014-08-15 17:55:06]

LGTM

Thanks.

[iant, 2014-08-15 18:33:35]

*** Submitted as https://code.google.com/p/go/source/detail?r=4ea7fb0f5747 ***

cmd/gc: disallow pointer constants

Fixes issue 7760.

LGTM=iant
R=iant, remyoudompheng
CC=golang-codereviews
https://codereview.appspot.com/130720043

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