[LLVMdev] 3.4 branch gcc 4.9 build error

[Alp Toker]

On 15/05/2014 22:12, Tom Stellard wrote:
> On Thu, May 15, 2014 at 01:38:32PM +0200, Tuncer Ayaz wrote:
>> On Thu, 15 May 2014 02:25:30 +0200, Tom Stellard wrote:
>>
>>> On Sat, May 10, 2014 at 11:48:23PM +0200, Tuncer Ayaz wrote:
>>>> Tom,
>>>>
>>>> now that 3.4.1 is out, any chance of a 3.4.2 with just the three
>>>> fixes or at least merging them to the 3.4 branch?
>>> I've pushed the two approved patches to the 3.4 branch, can you
>>> verify that they work with gcc 4.9.
>> Thanks, Tom.
>>
>> Fresh (svn rev 208853) checkout of llvm, clang, etc:
>>
>> llvm[1]: Compiling APFloat.cpp for Release build
>> In file included from APFloat.cpp:15:
>> In file included from /tmp/llvm/include/llvm/ADT/APFloat.h:20:
>> In file included from /tmp/llvm/include/llvm/ADT/APInt.h:19:
>> In file included from /tmp/llvm/include/llvm/ADT/ArrayRef.h:14:
>> In file included from /tmp/llvm/include/llvm/ADT/SmallVector.h:17:
>> In file included from /tmp/llvm/include/llvm/Support/AlignOf.h:19:
>> /usr/lib64/[...]/c++/4.9.0/cstddef:51:11: error:
>>        no member named 'max_align_t' in the global namespace
>>    using ::max_align_t;
>>          ~~^
>> 1 error generated.
>>
> Is this trunk or the 3.4 branch?
>
>> As the fixes got merged to the release_34 branch, I went to check the
>> local configure options and noticed I was passing --enable-cxx11. If I
>> omit that, there's no max_align_t error. I don't remember when I added
>> that, but it used to build prior to gcc 4.9. Just so I understand, is
>> that flag meant to be enabled (and known to work) when llvm is built
>> by clang, or is that also in need of fixing for gcc 4.9?
> So clang/llvm will only fail to build with gcc 4.9 if the --enable-cxx11 flag is used?

The underlying problem was that, without the fix, clang's C++11 mode 
didn't work *at all* with system headers shipped by GCC 4.9.

So the failure to self-host with --enable-cxx11 mentioned by Tuncer is 
really only a secondary symptom of the wider problem reported by 
distributions.

Alp.


>
> -Tom
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