Move OS/compiler/feature detection to public v8config.h header.

Move OS/compiler/feature detection to public v8config.h header.

From now on the v8config.h header should be the one and
only file where we do (freaky) checks to detect OS, C++
compiler or certain compiler features. Since we need that
both internally and for the public API, the new v8config.h
is the proper place to add (everything is prefixed with V8_
so we are safe).

R=svenpanne@chromium.org

Committed: https://code.google.com/p/v8/source/detail?r=16281

[Benedikt Meurer, 2013-08-22 09:35:59]

As discussed offline, here's the v8config.h approach, which does not depend on
GYP. The V8_OS_ defines are compatible with what chromium does.

[Sven Panne, 2013-08-23 07:29:08]

lgtm

[Benedikt Meurer, 2013-08-23 07:32:38]

Committed patchset #3 manually as r16281.

[Nico, 2014-11-26 21:43:20]

thakis@chromium.org changed reviewers:
+ thakis@chromium.org

[Nico, 2014-11-26 21:43:20]

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h
File include/v8config.h (right):

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h#newcod...
include/v8config.h:118: #if defined(__clang__)
This doesn't look like a good approach to me. Clang tries to look like gcc, or
like cl.exe, depending on how it's invoked. All of other chrome's projects let
their COMPILER_GCC include clang in gcc mode, and their COMPILER_MSVC clang in
ms mode, and then use a dedicated #if __clang__ in the few places where this
doesn't work out. Was this approach considered?

The concrete reason why I'm looking at this: the V8_INT64_C macros are
incorrectly set when building with clang on Windows because clang isn't allowed
to go down the V8_CC_MSVC path in macros.h – and the non-msvc path then thinks
that "l" is the correct format string for pointers. But while "long" is 64bit in
64bit builds on posix, it isn't on Windows. I could fix that macro, but I think
a better fix would be to get rid of V8_CC_CLANG and let clang be included in the
gcc and msvc code paths. I'm happy to do this work if this sounds acceptable to
you.

[Benedikt Meurer, 2014-12-01 18:02:01]

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h
File include/v8config.h (right):

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h#newcod...
include/v8config.h:118: #if defined(__clang__)
So you're talking about either setting both V8_CC_CLANG and V8_CC_GNU or setting
both V8_CC_CLANG and V8_CC_MSVC? That'll require some careful changes to several
files.

[Nico, 2014-12-01 18:03:48]

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h
File include/v8config.h (right):

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h#newcod...
include/v8config.h:118: #if defined(__clang__)
On 2014/12/01 18:02:00, Benedikt Meurer wrote:
> So you're talking about either setting both V8_CC_CLANG and V8_CC_GNU or
setting
> both V8_CC_CLANG and V8_CC_MSVC?

Yes, I'd let clang set V8_CC_GNU or V8_CC_MSVC (depending on which mode it
emulates).

Maybe I'd even try to get rid of V8_CC_CLANG.

[Nico, 2014-12-01 20:10:08]

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h
File include/v8config.h (right):

https://codereview.chromium.org/23248006/diff/11001/include/v8config.h#newcod...
include/v8config.h:118: #if defined(__clang__)
On 2014/12/01 18:02:00, Benedikt Meurer wrote:
> So you're talking about either setting both V8_CC_CLANG and V8_CC_GNU or
setting
> both V8_CC_CLANG and V8_CC_MSVC? That'll require some careful changes to
several
> files.

It looks like it Just Works: https://codereview.chromium.org/757553004/

Maybe I didn't look for the right files? Were you thinking of anything in
particular?