[utils] Improvements to check_cfc.py to work better with build systems

[russell.gallop]

Summary

This revision has a couple of small changes to make check_cfc.py made so it works better with build systems.

gcc/clang options which output dependency files instead of object files (e.g. -M, -MM) are identified and checks are not performed in these cases.

When reporting a check failure, the input file name is reported which can help to identify where the problem was in large build logs, particularly with parallel builds.

Please let me know if okay to commit?

[• rafael]

LGTM

utils/check_cfc/check_cfc.py

if infile:
         args[infile_idx] = input_file
         return args
     else:
         # Could not find input file
         assert False
 
 def is_normal_compile(args):
     """Check if this is a normal compile which will output an object file rather
-    than a preprocess or link."""
+    than a preprocess or link. args is a list of command line arguments."""
     compile_step = '-c' in args
     # Bitcode cannot be disassembled in the same way
     bitcode = '-flto' in args or '-emit-llvm' in args
     # Version and help are queries of the compiler and override -c if specified
     query = '--version' in args or '--help' in args
+    # Options to output dependency files for make
+    dependency = '-M' in args or '-MM' in args
     # Check if the input is recognised as a source file (this may be too
     # strong a restriction)
     input_is_valid = bool(get_input_file(args))
-    return compile_step and not bitcode and not query and input_is_valid
+    return compile_step and not bitcode and not query and not dependency and input_is_valid
 
 def run_step(command, my_env, error_on_failure):
     """Runs a step of the compilation. Reports failure as exception."""
     # Need to use shell=True on Windows as Popen won't use PATH otherwise.
     p = subprocess.Popen(command, stdout=subprocess.PIPE,
                          stderr=subprocess.PIPE, env=my_env, shell=is_windows())
     (stdout, stderr) = p.communicate()
     if p.returncode != 0:
"""
     for check_name in checks:
         if config.getboolean('Checks', check_name):
             class_ = getattr(current_module, check_name)
             checker = class_(temp_output_file_orig)
             try:
                 checker.perform_check(arguments_a, my_env)
             except WrapperCheckException as e:
                 # Check failure
-                print(e.msg, file=sys.stderr)
+                print("{} {}".format(get_input_file(arguments_a), e.msg), file=sys.stderr)
 
                 # Remove file to comply with build system expectations (no
                 # output file if failed)
                 os.remove(output_file_orig)
                 sys.exit(1)
 
             except WrapperStepException as e:
                 # Compile step failure

utils/check_cfc/test_check_cfc.py

def test_is_normal_compile(self):
             check_cfc.is_normal_compile(['clang', '-c', 'test.s', '-o', 'test.o']))
         self.assertFalse(
             check_cfc.is_normal_compile(['clang', '-c', 'test.ii', '-o', 'test.o']))
         # Specifying --version and -c is not a normal compile
         self.assertFalse(
             check_cfc.is_normal_compile(['clang', '-c', 'test.cpp', '--version']))
         self.assertFalse(
             check_cfc.is_normal_compile(['clang', '-c', 'test.cpp', '--help']))
+        # Outputting dependency files is not a normal compile
+        self.assertFalse(
+            check_cfc.is_normal_compile(['clang', '-c', '-M', 'test.cpp']))
+        self.assertFalse(
+            check_cfc.is_normal_compile(['clang', '-c', '-MM', 'test.cpp']))
+        # Creating a dependency file as a side effect still outputs an object file
+        self.assertTrue(
+            check_cfc.is_normal_compile(['clang', '-c', '-MD', 'test.cpp']))
+        self.assertTrue(
+            check_cfc.is_normal_compile(['clang', '-c', '-MMD', 'test.cpp']))
 
     def test_replace_output_file(self):
         self.assertEqual(check_cfc.replace_output_file(
             ['clang', '-o', 'test.o'], 'testg.o'), ['clang', '-o', 'testg.o'])
         self.assertEqual(check_cfc.replace_output_file(
             ['clang', '-otest.o'], 'testg.o'), ['clang', '-otestg.o'])
         with self.assertRaises(Exception):
             check_cfc.replace_output_file(['clang'], 'testg.o')