[petsc-dev] defaulting gnu compilers on Apple

[Satish Balay]

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:

> ~/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