[petsc-dev] defaulting gnu compilers on Apple

[Barry Smith]

On Oct 31, 2013, at 1:03 PM, Satish Balay <balay at mcs.anl.gov> wrote:

> On Thu, 31 Oct 2013, Satish Balay wrote:
> 
>> On Thu, 31 Oct 2013, Barry Smith wrote:
>> 
>>>> As of now - the differences this wrapper might provide is not obvious to us.
>>>> 
>>>> So for practical purposes '/usr/bin/gcc' is same as 'clang’.
>>> 
>>>   How can you say that. We simply do not know.
>> 
>> 1. /usr/bin/gcc says its clang [in verbose mode] 
>> 
>> Executing: /opt/HPC/mpich-3.0.4-gcc4.2/bin/mpicc --version
>> stdout:
>> Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn)
>> Target: x86_64-apple-darwin13.0.0
>> 
>> 2. /usr/bin/gcc says its clang in error messages:
> 
> 
> 4. Missed mentioning: '/usr/bin/gcc' does not accept GNU-gcc options.

   So does configure at least answer no when you do compiles.isGNU?

   Barry

> [as indicated below]
> 
> Satish
> 
>> 
>>> ~/s/s/w/tmp ❯❯❯ gcc -fsel-sched-pipelining file.c
>>> 
>>> clang: warning: argument unused during compilation: '-fsel-sched-pipelining'
>> 
>> 3. And it accepts clang arguments that gcc does not.
>> 
>>> ~/s/s/w/tmp ❯❯❯ gcc --analyze file.c
>>> ~/s/s/w/tmp ❯❯❯ clang --analyze file.c
>> 
>> So - I conclude '/usr/bin/gcc' is clang - perhaps with a light-weight
>> wrapper [because the binaries don't match.] until someone can show
>> there is a difference in behavior in terms of 'works with clang - but
>> not with /usr/bin/gcc'
>> 
>> Satish