Fix compilation with GCC 4.8

Fix compilation with GCC 4.8

BUG=v8:2767, v8:2149
R=bmeurer@chromium.org

Committed: http://code.google.com/p/v8/source/detail?r=17641

[Jakob Kummerow, 2013-11-12 09:56:58]

PTAL.

The SEMI_STATIC_JOIN fix using __attribute__((unused)) is what boost does too.

I've tested this CL on Gentoo with GCC 4.8.1 and on Ubuntu Precise with GCC
4.6.3.

[Benedikt Meurer, 2013-11-12 10:20:15]

LGTM

[Benedikt Meurer, 2013-11-12 10:31:42]

Sorry, NOT LGTM.

https://codereview.chromium.org/69413002/diff/1/src/checks.h
File src/checks.h (right):

https://codereview.chromium.org/69413002/diff/1/src/checks.h#newcode272
src/checks.h:272: __attribute__((unused))  // Silence GCC-4.8's warnings.
This will fail on Visual Studio. Please add an appropriate define
V8_HAS_ATTRIBUTE_UNUSED to include/v8config.h (Clang requires an __has_attribute
test, whereas for GCC a version test is sufficient), and define a V8_UNUSED
macro based on that, similar to what we do with the other compiler specific
stuff.

[Jakob Kummerow, 2013-11-12 12:01:28]

Thanks, please take another look.

https://codereview.chromium.org/69413002/diff/1/src/checks.h
File src/checks.h (right):

https://codereview.chromium.org/69413002/diff/1/src/checks.h#newcode272
src/checks.h:272: __attribute__((unused))  // Silence GCC-4.8's warnings.
On 2013/11/12 10:31:42, Benedikt Meurer wrote:
> This will fail on Visual Studio. Please add an appropriate define
> V8_HAS_ATTRIBUTE_UNUSED to include/v8config.h (Clang requires an
__has_attribute
> test, whereas for GCC a version test is sufficient), and define a V8_UNUSED
> macro based on that, similar to what we do with the other compiler specific
> stuff.

Done.

[Benedikt Meurer, 2013-11-12 12:03:35]

On 2013/11/12 12:01:28, Jakob wrote:
> Thanks, please take another look.
> 
> https://codereview.chromium.org/69413002/diff/1/src/checks.h
> File src/checks.h (right):
> 
> https://codereview.chromium.org/69413002/diff/1/src/checks.h#newcode272
> src/checks.h:272: __attribute__((unused))  // Silence GCC-4.8's warnings.
> On 2013/11/12 10:31:42, Benedikt Meurer wrote:
> > This will fail on Visual Studio. Please add an appropriate define
> > V8_HAS_ATTRIBUTE_UNUSED to include/v8config.h (Clang requires an
> __has_attribute
> > test, whereas for GCC a version test is sufficient), and define a V8_UNUSED
> > macro based on that, similar to what we do with the other compiler specific
> > stuff.
> 
> Done.

LGTM

[Jakob Kummerow, 2013-11-12 12:09:45]

Committed patchset #2 manually as r17641 (presubmit successful).