>From what I remember - I think Jed mentioned - clang supports most of the usual gcc options. Perhaps you can try the following to see if they are identical.
<<< clang option that gcc does not support >>>> balay@mockingbird /home/balay/junk $ gcc --analyze sizeof.c gcc: error: unrecognized command line option ‘--analyze’ balay@mockingbird /home/balay/junk $ clang --analyze sizeof.c balay@mockingbird /home/balay/junk <<<< gcc option that clang does not support >>>> balay@mockingbird /home/balay/junk $ clang -fsel-sched-pipelining sizeof.c clang: warning: argument unused during compilation: '-fsel-sched-pipelining' balay@mockingbird /home/balay/junk Satish On Thu, 31 Oct 2013, Barry Smith wrote: > > They are not aliases but I cannot determine if there is a difference in > functionality > > ~/Src/petsc next $ gcc --version > Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr > --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1 > Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) > Target: x86_64-apple-darwin13.0.0 > Thread model: posix > ~/Src/petsc next $ clang --version > Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) > Target: x86_64-apple-darwin13.0.0 > Thread model: posix > ~/Src/petsc next $ ls -l /usr/bin/gcc > -rwxr-xr-x 1 root wheel 14224 Oct 22 20:01 /usr/bin/gcc > ~/Src/petsc next $ ls -l /usr/bin/clang > -rwxr-xr-x 1 root wheel 14224 Oct 22 20:01 /usr/bin/clang > ~/Src/petsc next $ diff /usr/bin/clang /usr/bin/gcc > Binary files /usr/bin/clang and /usr/bin/gcc differ > ~/Src/petsc next $ g++ --version > Configured with: --prefix=/Applications/Xcode.app/Contents/Developer/usr > --with-gxx-include-dir=/Applications/Xcode.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/c++/4.2.1 > Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) > Target: x86_64-apple-darwin13.0.0 > Thread model: posix > ~/Src/petsc next $ clang++ --version > Apple LLVM version 5.0 (clang-500.2.79) (based on LLVM 3.3svn) > Target: x86_64-apple-darwin13.0.0 > Thread model: posix > ~/Src/petsc next $ diff /usr/bin/clang++ /usr/bin/g++ > Binary files /usr/bin/clang++ and /usr/bin/g++ differ > > man gcc returns the manual page for gcc (with its huge number of crazy gnu > specific stuff) while man clang gives back a smaller clang/llvm manual page. > > I guess someone needs to bite the bullet and test the gcc options that are > not clang options and see if they work with /usr/bin/gcc > > If Xcode’s gcc does not support gcc options then we should not default to > using it since that is way confusing! > > Barry > > > > On Oct 31, 2013, at 12:12 AM, Sean Farley <[email protected]> > wrote: > > > > > [email protected] writes: > > > >> On Thu, 31 Oct 2013, Sean Farley wrote: > >> > >>> > >>> [email protected] writes: > >>> > >>>> unless everyone is using xcode5 - I think gcc/g++ is a safer default. > >>> > >>> Apple stopped shipping gcc with Xcode 4.2 [1]. Since that version, > >>> everyone has been using the llvm backend. > >> > >> The isse is clang frontend with xcode4 is buggy [breaks with petsc build] > >> > >> http://lists.mcs.anl.gov/pipermail/petsc-dev/2013-October/thread.html > > > > It would appear so. > > > >>> Only in version >= 5.0 has > >>> llvm-gcc been dropped. And in Mavericks only libc++ (and not libstdc++) > >>> is shipped. > >>> > >>> [1] http://en.wikipedia.org/wiki/Xcode#Toolchain_Versions > >> > >> Since /usr/bin/gcc is an alias to clang in Xcode5 - there is no need > >> to change defaults on OSX as Barry is suggesting? > > > > Probably, but I haven't tested. > >
