code review 2102043: cgo: add typedef for uintptr in generated headers

cgo: add typedef for uintptr in generated headers

Fixes issue 1046.

[adg, 2010-09-07 12:09:44]

Hello r (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[adg, 2010-09-07 12:36:58]

This was intended for rsc, not r. Sorry.

[rsc1, 2010-09-07 13:24:50]

This is gcc.  You can use

typedef unsigned long uintptr;

Russ

[iant2, 2010-09-07 17:32:38]

Russ Cox <rsc@google.com> writes:

> This is gcc.  You can use
>
> typedef unsigned long uintptr;

Heck, since it's gcc, you can use

typedef __UINTPTR_TYPE__ uintptr;

I don't know if this matters here, but on Windows for 64-bit x86,
unsigned long is 32 bits, and uintptr is 64 bits for which you need
unsigned long long.

Ian

[adg, 2010-09-08 05:35:25]

x
On 8 September 2010 03:32, Ian Lance Taylor <iant@google.com> wrote:
> Russ Cox <rsc@google.com> writes:
>
>> This is gcc.  You can use
>>
>> typedef unsigned long uintptr;
>
> Heck, since it's gcc, you can use
>
> typedef __UINTPTR_TYPE__ uintptr;

Using this I get:

_cgo_export.h:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
‘__attribute__’ before ‘uintptr’

My /usr/include/stdint.h doesn't refer to UINTPTR_TYPE anywhere.

> I don't know if this matters here, but on Windows for 64-bit x86,
> unsigned long is 32 bits, and uintptr is 64 bits for which you need
> unsigned long long.

If cgo is to work under windows, then should the current version
remain? Otherwise if the above won't work I'll just do

  typedef unsigned long uintptr;

Andrew

[iant2, 2010-09-08 05:48:39]

Andrew Gerrand <adg@golang.org> writes:

> x
> On 8 September 2010 03:32, Ian Lance Taylor <iant@google.com> wrote:
>> Russ Cox <rsc@google.com> writes:
>>
>>> This is gcc.  You can use
>>>
>>> typedef unsigned long uintptr;
>>
>> Heck, since it's gcc, you can use
>>
>> typedef __UINTPTR_TYPE__ uintptr;
>
> Using this I get:
>
> _cgo_export.h:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
> ‘__attribute__’ before ‘uintptr’
>
> My /usr/include/stdint.h doesn't refer to UINTPTR_TYPE anywhere.

Ah, my apologies.  That only works with gcc 4.5 or later, so it's not
yet useful for cgo.


>> I don't know if this matters here, but on Windows for 64-bit x86,
>> unsigned long is 32 bits, and uintptr is 64 bits for which you need
>> unsigned long long.
>
> If cgo is to work under windows, then should the current version
> remain? Otherwise if the above won't work I'll just do
>
>   typedef unsigned long uintptr;

Another option would be __SIZE_TYPE__ which gcc has supported for quite
a while.  In general __SIZE_TYPE__ should give you the right size for a
pointer.

In practice "unsigned long" will be fine except on 64-bit Windows.

Ian

[adg, 2010-09-08 05:52:15]

Hello rsc, rsc1, iant2 (cc: golang-dev@googlegroups.com),

I'd like you to review this change.

[adg, 2010-09-08 05:53:28]

On 8 September 2010 15:48, Ian Lance Taylor <iant@google.com> wrote:
> Andrew Gerrand <adg@golang.org> writes:
>
>> x
>> On 8 September 2010 03:32, Ian Lance Taylor <iant@google.com> wrote:
>>> Russ Cox <rsc@google.com> writes:
>>>
>>>> This is gcc.  You can use
>>>>
>>>> typedef unsigned long uintptr;
>>>
>>> Heck, since it's gcc, you can use
>>>
>>> typedef __UINTPTR_TYPE__ uintptr;
>>
>> Using this I get:
>>
>> _cgo_export.h:9: error: expected ‘=’, ‘,’, ‘;’, ‘asm’ or
>> ‘__attribute__’ before ‘uintptr’
>>
>> My /usr/include/stdint.h doesn't refer to UINTPTR_TYPE anywhere.
>
> Ah, my apologies.  That only works with gcc 4.5 or later, so it's not
> yet useful for cgo.
>
>
>>> I don't know if this matters here, but on Windows for 64-bit x86,
>>> unsigned long is 32 bits, and uintptr is 64 bits for which you need
>>> unsigned long long.
>>
>> If cgo is to work under windows, then should the current version
>> remain? Otherwise if the above won't work I'll just do
>>
>>   typedef unsigned long uintptr;
>
> Another option would be __SIZE_TYPE__ which gcc has supported for quite
> a while.  In general __SIZE_TYPE__ should give you the right size for a
> pointer.

That works. I've used it instead.

> In practice "unsigned long" will be fine except on 64-bit Windows.

Let's see if __SIZE_TYPE__ works under MinGW I guess.

Andrew

[iant, 2010-09-08 13:59:41]

LGTM but see what Russ thinks.

[rsc1, 2010-09-08 14:08:21]

LGTM

[adg, 2010-09-08 23:24:56]

*** Submitted as http://code.google.com/p/go/source/detail?r=05617b5c4263 ***

cgo: add typedef for uintptr in generated headers

Fixes issue 1046.

R=rsc, iant
CC=golang-dev
http://codereview.appspot.com/2102043

Committer: Andrew Gerrand <adg@golang.org>