Hi Erik, On Apr 11, 2013, at 7:43 PM, Erik Bray wrote:

One possible solution, albeit more complex code-wise than compiling that single file as a static lib, would be to subclass the compiler class you want to use and override its _compile() method, which is the one responsible for compiling a single file. You can then override the arguments in there. Look, for example, at distutils.unixcompiler.UnixCCompiler._compile.

I shudder every time I think about subclassing one of the compiler classes. I've done it before, based on suggestions from this list, but I had no sense of how it actually worked. Instead, I wrote a wrapper script, at the end of this email, which can be used like this: env CC=$PWD/filter_gcc python setup.py build It sniffs the command-line and keeps "-mssse3" for the right file, otherwise it removes that option. It then calls gcc with the tweaked arguments. Unlike subclassing, I understand how this one works. :) Cheers, Andrew dalke@dalkescientific.com #!/usr/bin/env python # chemfp by default assumes the --with-ssse3 flag, which enables # compiler-specific option to enable the SSSE3 intrinsics. # # You can disable this using --without-ssse3. # # The code which requires the SSSE3 specific intrinsics will only be # run when chemfp, at run-time, determines that the CPU supports the # SSSE3 instruction set. This is as it should be. Unfortunately, the # -mssse3 compiler flag also tells gcc that it's okay to use # SSSE3-specific instructions in the rest of the code. This causes a # bus error if chemfp is then used on a CPU which doesn't support the # correct instruction set. Unfortunately, I don't have the ability to # use a non-ssse3 code path for this case. # # This is only a problem if: # - you use the same binary on multiple platforms, where # - some machines do not have the SSSE3 instruction set AND # - some machines have the SSSE3 instruction set AND # - the machines with the SSSE3 instruction set do not support POPCNT. # # (If all of your SSSE3 machines also support POPCNT then it's okay to # use --without-ssse3, because the POPCNT instruction is always faster # than the SSSE3-based popcount implementation.) # # This script, filter_gcc, is a workaround for the problem. Only one # file needs the -mssse3 option. The best solution is to tell Python's # setup.py to compile src/popcount_SSSE3.c with -mssse3 enabled and to # leave out that flag for the other files. Unfortunately, setup.py # doesn't make that easy. # # filter_gcc acts as a filter layer between setup.py and gcc. It's # used like this: # # env CC=$PWD/filter_gcc python setup.py build # # This tells setup.py to use $PWD/filter_gcc (ie, this script) as an # alternate C compiler. This script run and checks if setup.py is # attempting to compile popcount_SSSE3.c. If so, it leaves the -mssse3 # flag in place (if it exists). Otherwise, it removes the flag (if it # exists). import sys import subprocess CC = "gcc" # The real C compiler args = sys.argv[1:] #print "Called with", args # Check to see if I should remove the "-mssse3" flag from the args. remove_mssse3 = True for arg in args: if "popcount_SSSE3.c" in arg: remove_mssse3 = False break if remove_mssse3: # Go ahead and remove the "-mssse3" try: args.remove("-mssse3") except ValueError: # This can happen if someone does: # env CC=$PWD/filter_gcc python setup.py build --without-ssse3 pass assert args, "Missing exec args" # Use the correct C compiler args = [CC] + args #print " -->", " ".join(args) # Run the new command, and report any errors. try: retcode = subprocess.call(args) except OSError, err: cmd = " ".join(args) raise SystemExit("Failed to execute %r: %s" % (cmd, err)) if retcode: raise SystemExit(retched)