Bug 83999 – Make NullPtr.h compile with clang -std=c++11 and libstdc++4.2

• Component: New Bugs
• Status: RESOLVED FIXED

[Nico Weber]

Make NullPtr.h compile with clang -std=c++11 and libstdc++4.2

[Nico Weber]

Created attachment 137244 [details]
Patch

[Nico Weber]

Created attachment 137245 [details]
Patch

[Nico Weber]

Comment on attachment 137244 [details]
Patch

cpp file too

[Nico Weber]

Created attachment 137246 [details]
Patch

[WebKit Review Bot]

Attachment 137246 [details] did not pass style-queue:

Failed to run "['Tools/Scripts/check-webkit-style', '--diff-files', u'Source/WTF/ChangeLog', u'Source/WTF/wtf/Nu..." exit_code: 1
Source/WTF/wtf/NullPtr.h:50:  Code inside a namespace should not be indented.  [whitespace/indent] [4]
Total errors found: 1 in 2 files


If any of these errors are false positives, please file a bug against check-webkit-style.

[Nico Weber]

Created attachment 137247 [details]
Patch

[Nico Weber]

Created attachment 137248 [details]
Patch

[Nico Weber]

(The __GLIBCXX__ version that belongs to gcc4.6 is from http://gcc.gnu.org/onlinedocs/libstdc++/manual/abi.html )

[Sam Weinig]

Comment on attachment 137248 [details]
Patch

View in context: https://bugs.webkit.org/attachment.cgi?id=137248&action=review

> Source/WTF/wtf/NullPtr.h:48
> +// libstdc++ supports nullptr_t starting with gcc 4.6.
> +#if defined(__GLIBCXX__) && __GLIBCXX__ < 20110325
> +#define HAS_NULLPTR_T 0
>  #else
> +#define HAS_NULLPTR_T 1
> +#endif
>  
> +#if !HAS_NULLPTR_T
> +// Compiler supports nullptr, but standard library doesn't have nullptr_t.

I don't think this extra HAS_NULLPTR_T macro is helpful.  I think the typedef can just go in the correct macro branch.  Also, is there a case where this might be hit, but the compiler doesn't support decltype?

[Nico Weber]

(In reply to comment #9)
> (From update of attachment 137248 [details])
> View in context: https://bugs.webkit.org/attachment.cgi?id=137248&action=review
> 
> > Source/WTF/wtf/NullPtr.h:48
> > +// libstdc++ supports nullptr_t starting with gcc 4.6.
> > +#if defined(__GLIBCXX__) && __GLIBCXX__ < 20110325
> > +#define HAS_NULLPTR_T 0
> >  #else
> > +#define HAS_NULLPTR_T 1
> > +#endif
> >  
> > +#if !HAS_NULLPTR_T
> > +// Compiler supports nullptr, but standard library doesn't have nullptr_t.
> 
> I don't think this extra HAS_NULLPTR_T macro is helpful.  I think the typedef can just go in the correct macro branch.

Done, thanks.

>  Also, is there a case where this might be hit, but the compiler doesn't support decltype?

It's possible :-) gcc added decltype in 4.3 and nullptr in 4.6 (http://en.wikipedia.org/wiki/Decltype , http://gcc.gnu.org/projects/cxx0x.html). MSVC added decltype in 2010, which is what Compiler.h checks for to set WTF_COMPILER_SUPPORTS_CXX_NULLPTR too. (_MSC_VER 1600 is 2010 according to http://msdn.microsoft.com/en-us/library/b0084kay.aspx ). I tested that this works with clang.

So it should be fine at least with gcc, msvc, and clang.

[Nico Weber]

Created attachment 137251 [details]
Patch

[Nico Weber]

> >  Also, is there a case where this might be hit, but the compiler doesn't support decltype?
> 
> It's possible :-) gcc added decltype in 4.3 and nullptr in 4.6 (http://en.wikipedia.org/wiki/Decltype , http://gcc.gnu.org/projects/cxx0x.html). MSVC added decltype in 2010, which is what Compiler.h checks for to set WTF_COMPILER_SUPPORTS_CXX_NULLPTR too. (_MSC_VER 1600 is 2010 according to http://msdn.microsoft.com/en-us/library/b0084kay.aspx ). I tested that this works with clang.
> 
> So it should be fine at least with gcc, msvc, and clang.

…also, that code is only compiled when libstdc++ from a gcc earlier than gcc4.6 is used. If gcc is used, this means its version is < 4.6 too, so it doesn't support nullptr and won't hit this block. So this can only happen with clang and libstdc++ (and other compilers that use libstdc++ that I don't know about).

[WebKit Review Bot]

Comment on attachment 137251 [details]
Patch

Attachment 137251 [details] did not pass chromium-ews (chromium-xvfb):
Output: http://queues.webkit.org/results/12412076

New failing tests:
fast/repaint/fixed-table-overflow-zindex.html
fast/repaint/scroll-fixed-reflected-layer.html
fast/repaint/fixed-scale.html
fast/repaint/fixed-tranformed.html

[WebKit Review Bot]

Created attachment 137254 [details]
Archive of layout-test-results from ec2-cr-linux-03

The attached test failures were seen while running run-webkit-tests on the chromium-ews.
Bot: ec2-cr-linux-03  Port: <class 'webkitpy.common.config.ports.ChromiumXVFBPort'>  Platform: Linux-2.6.35-28-virtual-x86_64-with-Ubuntu-10.10-maverick

[WebKit Review Bot]

Comment on attachment 137251 [details]
Patch

Clearing flags on attachment: 137251

Committed r114227: <http://trac.webkit.org/changeset/114227>

[WebKit Review Bot]

All reviewed patches have been landed.  Closing bug.