Subzero: Print defaults as appropriate in python script help text.

pydir/crosstest.py

 #!/usr/bin/env python2
 
 import argparse
 import os
 import re
 import subprocess
 import sys
 import tempfile
 
 from utils import shellcmd
@@ skipping 19 matching lines @@
     argparser = argparse.ArgumentParser(description=desc)
     argparser.add_argument('--test', required=True, action='append',
                            metavar='TESTFILE_LIST',
                            help='List of C/C++/.ll files with test functions')
     argparser.add_argument('--driver', required=True,
                            metavar='DRIVER',
                            help='Driver program')
     argparser.add_argument('--target', required=False, default='x8632',
                            choices=arch_map.keys(),
                            metavar='TARGET',
-                           help='Translation target architecture')
+                           help='Translation target architecture.' +
+                                ' Default %(default)s.')
     argparser.add_argument('-O', required=False, default='2', dest='optlevel',
                            choices=['m1', '-1', '0', '1', '2'],
                            metavar='OPTLEVEL',
                            help='Optimization level ' +
-                                '(m1 and -1 are equivalent)')
+                                '(m1 and -1 are equivalent).' +
+                                ' Default %(default)s.')
     argparser.add_argument('--mattr',  required=False, default='sse2',
                            dest='attr', choices=['sse2', 'sse4.1'],
-                           metavar='ATTRIBUTE', help='Target attribute')
+                           metavar='ATTRIBUTE',
+                           help='Target attribute. Default %(default)s.')
     argparser.add_argument('--prefix', required=True,
                            metavar='SZ_PREFIX',
                            help='String prepended to Subzero symbol names')
     argparser.add_argument('--output', '-o', required=True,
                            metavar='EXECUTABLE',
                            help='Executable to produce')
     argparser.add_argument('--dir', required=False, default='.',
                            metavar='OUTPUT_DIR',
-                           help='Output directory for all files')
+                           help='Output directory for all files.' +
+                                ' Default "%(default)s".')
     argparser.add_argument('--crosstest-bitcode', required=False,
                            default=1, type=int,
                            help='Compile non-subzero crosstest object file ' +
                            'from the same bitcode as the subzero object. ' +
-                           'If 0, then compile it straight from source.')
+                           'If 0, then compile it straight from source.' +
+                           ' Default %(default)d.')
     args = argparser.parse_args()
 
     nacl_root = FindBaseNaCl()
     # Prepend host_x86_32/bin to $PATH.
     os.environ['PATH'] = nacl_root + \
         '/toolchain/linux_x86/pnacl_newlib/host_x86_32/bin' + \
         os.pathsep + os.environ['PATH']
 
     objs = []
     remove_internal = re.compile('^define internal ')
@@ skipping 62 matching lines @@
             objs.append(bitcode)
 
     # Use 'clang szrt.c'  -or-  'clang++ szrt.cpp'
     objs.append((
             '{root}/toolchain_build/src/subzero/runtime/szrt.{ext}'
             ).format(root=nacl_root, ext='c' if pure_c else 'cpp'))
     linker = 'clang' if pure_c else 'clang++'
     shellcmd([linker, '-g', '-m32', args.driver] +
              objs +
              ['-lm', '-lpthread', '-o', os.path.join(args.dir, args.output)])