llvm dev - Jul 2016 - GCC prerequisites for building LLVM head?

Is there is minimum required version for GCC to build LLVM from the head
revision?

 

I have GCC v4.9.3, but 'Tools/sancov/sancov.cc' won't build because
'std::to_string' does not exist.  When running CMake it did not flag GCC
v4.9.3 as too old, and it is passing the '-std=gnu++11' option, but
apparently this version of GCC is not fully C++ 11 compliant, or at least
its C++ library isn't.

 

Everything else builds.

 

Thanks,

 

            MartinO

 

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On 6 July 2016 at 08:46, Martin J. O'Riordan via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> Is there is minimum required version for GCC to build LLVM from the head
> revision?
Last I checked it was 4.7. The CMake files also tell me that's correct:

modules/CheckCompilerVersion.cmake:
# Check if the host compiler is new enough. LLVM requires at least GCC 4.7,

> I have GCC v4.9.3, but ‘Tools/sancov/sancov.cc’ won’t build because
> ‘std::to_string’ does not exist.  When running CMake it did not flag GCC
> v4.9.3 as too old, and it is passing the ‘-std=gnu++11’ option, but
> apparently this version of GCC is not fully C++ 11 compliant, or at least
> its C++ library isn’t.
This sounds odd. I have buildbots with 4.8.2 and 4.9.2 working perfectly.

Could this be a problem in your setup?

cheers,
--renato

I just checked with '-E' and I am picking up '<string>'
from:

    /usr/lib/gcc/i686-pc/cygwin/4.9.3/include/c++/string

all other C++ headers are coming from the same place.  The
'std::to_string' functions are not present in '<string>',
but they are located in '<bits/basic_string.h>' - which is
included.  Perhaps it is a broken Cygwin v4.9.3 package, but this is odd since
the source should be identical for the Cygwin versus Linux distros?  I can't
try this on Linux until tomorrow as I am working from home and don't have a
Linux setup that uses v4.9.3.

The 'std::to_string' functions are provided in a block that is
conditionally included as follows (line #2847 in my copy):

    #if __cplusplus >= 201103L && defined(_GLIBCXX_USE_C99)

    #include <ext/string_conversions.h>

    namespace std _GLIBCXX_VISIBILITY(default)
    {
    _GLIBCXX_BEGIN_NAMESPACE_VERSION

The test '__cplusplus >= 201103L' evaluates true in all previous
cases, so it would appear that '_GLIBCXX_USE_C99' is not being defined -
I can add this explicitly when I am configuring LLVM with CMake, but it seems a
bit strange that I need to.

Thanks,

	MartinO

-----Original Message-----
From: Renato Golin [mailto:renato.golin at linaro.org] 
Sent: 06 July 2016 10:12
To: Martin.ORiordan at movidius.com
Cc: LLVM Developers <llvm-dev at lists.llvm.org>
Subject: Re: [llvm-dev] GCC prerequisites for building LLVM head?

On 6 July 2016 at 08:46, Martin J. O'Riordan via llvm-dev <llvm-dev at
lists.llvm.org> wrote:
> Is there is minimum required version for GCC to build LLVM from the 
> head revision?
Last I checked it was 4.7. The CMake files also tell me that's correct:

modules/CheckCompilerVersion.cmake:
# Check if the host compiler is new enough. LLVM requires at least GCC 4.7,

> I have GCC v4.9.3, but ‘Tools/sancov/sancov.cc’ won’t build because 
> ‘std::to_string’ does not exist.  When running CMake it did not flag 
> GCC
> v4.9.3 as too old, and it is passing the ‘-std=gnu++11’ option, but 
> apparently this version of GCC is not fully C++ 11 compliant, or at 
> least its C++ library isn’t.
This sounds odd. I have buildbots with 4.8.2 and 4.9.2 working perfectly.

Could this be a problem in your setup?

cheers,
--renato

> On Jul 6, 2016, at 12:46 AM, Martin J. O'Riordan via llvm-dev
<llvm-dev at lists.llvm.org> wrote:
> 
> Is there is minimum required version for GCC to build LLVM from the head
revision?
>  
> I have GCC v4.9.3, but ‘Tools/sancov/sancov.cc <http://sancov.cc/>’
won’t build because ‘std::to_string’ does not exist.
We usually avoid using std::to_string AFAIK because not supported on every
platform we support.
Twine or llvm::utostr are good replacements for that, see r267829 or r257857 for
instance.

— 
Mehdi


>   When running CMake it did not flag GCC v4.9.3 as too old, and it is
passing the ‘-std=gnu++11’ option, but apparently this version of GCC is not
fully C++ 11 compliant, or at least its C++ library isn’t.
>  
> Everything else builds.
>  
> Thanks,
>  
>             MartinO
>  
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