[llvm-dev] GCC prerequisites for building LLVM head?

Martin J. O'Riordan via llvm-dev llvm-dev at lists.llvm.org
Wed Jul 6 03:04:34 PDT 2016

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


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)

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.



-----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:

# 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 
> 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?


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