Create a "no compile" drivers script in python to unittest compile time asserts.

tools/nocompile_driver.py

Index: tools/nocompile_driver.py
diff --git a/tools/nocompile_driver.py b/tools/nocompile_driver.py
new file mode 100755
index 0000000000000000000000000000000000000000..6b545ac0574d008e94fbc626c1837a672c41a340
--- /dev/null
+++ b/tools/nocompile_driver.py
@@ -0,0 +1,458 @@
+#!/usr/bin/python
+# Copyright (c) 2011 The Chromium Authors. All rights reserved.
+# Use of this source code is governed by a BSD-style license that can be
+# found in the LICENSE file.
+
+"""Implements a simple "negative compile" test for C++ on linux.
+
+Sometimes a C++ API needs to ensure that various usages cannot compile. To
+enable unittesting of these assertions, we use this python script to
+invoke gcc on a source file and assert that compilation fails.
+
+For more info, see:
+https://sites.google.com/a/chromium.org/dev/developers/testing/no-compile-tests

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

Not found for me; also would be nice to use the dev.chromium.org hostname.

[awong, 2011/09/09 01:01:43]

Strange...I'm able to see it.  I've updated with the dev.chromium.org version. 
Try it again?

[Ami GONE FROM CHROMIUM, 2011/09/09 17:17:12]

WFM now.

+"""
+
+import ast
+import locale
+import os
+import re
+import select
+import shlex
+import subprocess
+import sys
+import time
+
+
+class ConfigurationSyntaxError(Exception):
+  """Raised if the test configuration or specification cannot be parsed."""
+  pass
+
+
+# Matches lines that start with #if and have the substring TEST in the
+# conditional. Also extracts the comment.  This allows us to search for
+# lines like the following:
+#
+#   #ifdef NCTEST_NAME_OF_TEST  // [r'expected output']
+#   #if defined(NCTEST_NAME_OF_TEST)  // [r'expected output']
+#   #if NCTEST_NAME_OF_TEST  // [r'expected output']
+#   #elif NCTEST_NAME_OF_TEST  // [r'expected output']
+#   #elif DISABLED_NCTEST_NAME_OF_TEST  // [r'expected output']
+#
+# inside the unittest file.
+NCTEST_CONFIG_RE = re.compile(r'^#(?:el)?if.*\s+(\S*NCTEST\S*)\s*(//.*)?')
+
+
+# Matches and removes the defined() preprocesor predicate. This is useful
+# for test cases that use the preprocessor if-statement form:
+#
+#   #if defined(NCTEST_NAME_OF_TEST)
+#
+# Should be used to post-process the results found by NCTEST_CONFIG_RE.
+STRIP_DEFINED_RE = re.compile(r'defined\((.*)\)')
+
+
+# Used to grab the expectation from comment at the end of an #ifdef.  See
+# NCTEST_CONFIG_RE's comment for examples of what the format should look like.
+#
+# The extracted substring should be a python array of regular expressions.
+EXTRACT_EXPECTATION_RE = re.compile(r'//\s*(\[.*\])')
+
+
+# The header for the result file so that it can be compiled.
+RESULT_FILE_HEADER = """
+// This file is generated by the no compile test from:
+//   %s
+
+#include "base/logging.h"
+#include "testing/gtest/include/gtest/gtest.h"
+
+"""
+
+
+# The GUnit test function to output on a successful test completion.
+SUCCESS_GUNIT_TEMPLATE = """
+TEST(%s, %s) {
+  LOG(INFO) << "Took %f secs. Started at %f, ended at %f";
+}
+"""
+
+# The GUnit test function to output for a disabled test.
+DISABLED_GUNIT_TEMPLATE = """
+TEST(%s, %s) { }
+"""
+
+
+# Timeout constants.
+NCTEST_TERMINATE_TIMEOUT_SEC = 60

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

Channeling phajdan.jr, is there a standard timeout that'd be appropriate to
import into this module and use?  I don't know...

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

IWBN for that 60 to be significantly lower.  I see you have a side-thread going
about that.

[awong, 2011/09/09 01:01:43]

I have no clue what timeout would make sense.

[awong, 2011/09/09 01:01:43]

Yes...on my z600, it's pretty reliably < 2 seconds..

Originally this was 5, which I think is reasonable.  However, the try bots made
this go all crazy. Still trying to debug.

+NCTEST_KILL_TIMEOUT_SEC = NCTEST_TERMINATE_TIMEOUT_SEC + 2
+BUSY_LOOP_MAX_TIME_SEC = NCTEST_KILL_TIMEOUT_SEC * 2
+
+
+def ValidateInput(parallelism, sourcefile_path, cflags, resultfile_path):
+  """Make sure the arguments being passed in are sane."""
+  assert parallelism >= 1
+  assert type(sourcefile_path) is str
+  assert type(cflags) is str
+  assert type(resultfile_path) is str
+
+
+def ParseExpectation(expectation_string):
+  """Extracts expectation definition from the trailing comment on the ifdef.
+
+  See the comment on NCTEST_CONFIG_RE for examples of the format we are parsing.
+
+  Args:
+    expectation_string: A string like '// [r'some_regex']
+
+  Returns:
+    A list of compiled regular expressions indicating all possible valid
+    compiler outputs.  If the list is empty, all outputs are considered valid.
+  """
+  if expectation_string is None:
+    raise ConfigurationSyntaxError('Test must specify expected output.')

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

I'm a bit surprised you still have ConfigurationSyntaxError anywhere (as opposed
to simply asserting).

[awong, 2011/09/09 01:01:43]

All gone.

+
+  match = EXTRACT_EXPECTATION_RE.match(expectation_string)
+  assert match
+
+  raw_expectation = ast.literal_eval(match.group(1))
+  if type(raw_expectation) is not list:
+    raise ConfigurationSyntaxError(
+        'Expectations must be a list of regexps. Instead, got %s' %
+        repr(raw_expectation))
+
+  expectation = []
+  for regex_str in raw_expectation:
+    if type(regex_str) is not str:
+      raise ConfigurationSyntaxError(
+          '"%s" is not a regexp in %s' % (regex_str, expectation_string))
+    expectation.append(re.compile(regex_str))
+  return expectation
+
+
+def ExtractTestConfigs(sourcefile_path):
+  """Parses the soruce file for test configurations.
+
+  Each no-compile test in the file is separated by an ifdef macro.  We scan
+  the source file with the NCTEST_CONFIG_RE to find all ifdefs that look like
+  they demark one no-compile test and try to extract the test configuration
+  from that.
+
+  Args:
+    sourcefile_path: A string containing the path to the source file.
+
+  Returns:
+    A list of test configurations. Each test configuration is a dictionary of
+    the form:
+
+      { name: 'NCTEST_NAME'
+        suite_name: 'SOURCE_FILE_NAME'
+        expectations: [re.Pattern, re.Pattern] }
+
+    The |suite_name| is used to generate a pretty gtest output on successful
+    completion of the no compile test.
+
+    The compiled regexps in |expectations| define the valid outputs of the
+    compiler.  If any one of the listed patterns matches either the stderr or
+    stdout from the compilation, and the compilation failed, then the test is
+    considered to have succeeded.  If the list is empty, than we ignore the
+    compiler output and just check for failed compilation. If |expectations|
+    is actually None, then this specifies a compiler sanity check test, which
+    should expect a SUCCESSFUL compilation.
+  """
+  sourcefile = open(sourcefile_path, 'r')
+
+  # Convert filename from underscores to CamelCase.
+  words = os.path.splitext(os.path.basename(sourcefile_path))[0].split('_')
+  words = [w.capitalize() for w in words]
+  suite_name = 'NoCompile' + ''.join(words)
+
+  # Start with at least the compiler sanity test.  You need to always have one
+  # sanity test to show that compiler flags and configuration are not just
+  # wrong.  Otherwise, having a misconfigured compiler, or an error in the
+  # shared portions of the .nc file would cause all tests to erroneously pass.
+  test_configs = [{'name': 'NCTEST_SANITY',
+                   'suite_name': suite_name,
+                   'expectations': None}]
+
+  for line in sourcefile:
+    match_result = NCTEST_CONFIG_RE.match(line)
+    if not match_result:
+      continue
+
+    groups = match_result.groups()
+
+    # Grab the name and remove the defined() predicate if there is one.
+    name = groups[0]
+    strip_result = STRIP_DEFINED_RE.match(name)
+    if strip_result:
+      name = strip_result.group(1)
+
+    # Read expectations if there are any.
+    test_configs.append({'name': name,
+                         'suite_name': suite_name,
+                         'expectations': ParseExpectation(groups[1])})
+  sourcefile.close()
+  return test_configs
+
+
+def StartTest(sourcefile_path, cflags, config):
+  """Start one negative compile test.
+
+  Args:
+    sourcefile_path: A string with path to the source file.
+    cflags: A string with all the CFLAGS to give to gcc. This string will be
+            split by shelex so becareful with escaping.

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

s/becareful/be careful/

[awong, 2011/09/09 01:01:43]

Done.

+    config: A dictionary describing the test.  See ExtractTestConfigs
+      for a description of the config format.
+
+  Returns:
+    A dictionary containing all the information about the started test. The
+    fields in the dictionary are as follows:
+      { 'proc': A subprocess object representing the compiler run.
+        'cmdline': A string containing the exectued command line.
+        'name': A string containing the name of the test.
+        'suite_name': A string containing the suite name to use when generating
+                      the gunit test result.
+        'terminate_timeout': The timestamp in seconds since the epoch after
+                             which the test should be terminated.
+        'kill_timeout': The timestamp in seconds since the epoch after which
+                        the test should be given a hard kill signal.
+        'started_at': A timestamp in seconds since the epoch for when this test
+                      was started.
+        'aborted_at': A timestamp in seconds since the epoch for when this test
+                      was aborted.  If the test completed successfully,
+                      this value is 0.
+        'finished_at': A timestamp in seconds since the epoch for when this
+                       test was successfully complete.  If the test is aborted,
+                       or running, this value is 0.
+        'expectations': A dictionary with the test expectations. See
+                        ParseExpectation() for the structure.
+        }
+  """
+  # TODO(ajwong): Get the compiler from gyp.
+  cmdline = ['g++']
+  cmdline.extend(shlex.split(cflags))
+  name = config['name']
+  expectations = config['expectations']
+  if expectations is not None:
+    cmdline.append('-D%s' % name)
+  cmdline.extend(['-o', '/dev/null', '-c', '-x', 'c++', sourcefile_path])
+
+  process = subprocess.Popen(cmdline, stdout=subprocess.PIPE,
+                             stderr=subprocess.PIPE)
+  now = time.time()
+  return {'proc': process,
+          'cmdline': ' '.join(cmdline),
+          'name': name,
+          'suite_name': config['suite_name'],
+          'terminate_timeout': now + NCTEST_TERMINATE_TIMEOUT_SEC,
+          'kill_timeout': now + NCTEST_KILL_TIMEOUT_SEC,
+          'started_at': now,
+          'aborted_at': 0,
+          'finished_at': 0,
+          'expectations': expectations}
+
+
+def PassTest(resultfile, test):
+  """Logs the result of a test started by StartTest(), or a disabled test
+  configuration.
+
+  Args:
+    resultfile: File object for .cc file that results are written to.
+    test: An instance of the dictionary returned by StartTest(), a
+          configuration from ExtractTestConfigs().
+  """
+  # The 'started_at' key is only added if a test has been started.
+  if 'started_at' in test:
+    resultfile.write(SUCCESS_GUNIT_TEMPLATE % (
+        test['suite_name'], test['name'],
+        test['finished_at'] - test['started_at'],
+        test['started_at'], test['finished_at']))
+  else:
+    resultfile.write(DISABLED_GUNIT_TEMPLATE % (
+        test['suite_name'], test['name']))
+
+
+def FailTest(resultfile, test, error, stdout=None, stderr=None):
+  """Logs the result of a test started by StartTest()
+
+  Args:
+    resultfile: File object for .cc file that results are written to.
+    test: An instance of the dictionary returned by StartTest()
+    error: A string containing the reason for the failure.
+    stdout: A string containing the test's output to stdout.
+    stderr: A string containing the test's output to stderr.
+  """
+  resultfile.write('#error %s Failed: %s\n' % (test['name'], error))
+  resultfile.write('#error compile line: %s\n' % test['cmdline'])
+  if stdout and len(stdout) != 0:
+    resultfile.write('#error %s stdout:\n' % test['name'])
+    for line in stdout.split('\n'):
+      resultfile.write('#error   %s\n' % line)
+
+  if stderr and len(stderr) != 0:
+    resultfile.write('#error %s stderr:\n' % test['name'])
+    for line in stderr.split('\n'):
+      resultfile.write('#error   %s\n' % line)
+  resultfile.write('\n')
+
+
+def ProcessTestResult(resultfile, test):
+  """Interprets and logs the result of a test started by StartTest()
+
+  Args:
+    resultfile: File object for .cc file that results are written to.
+    test: The dictionary from StartTest() to process.
+  """
+  # Snap a copy of stdout and stderr into the test dictionary immediately
+  # cause we can only call this once on the Popen object, and lots of stuff
+  # below will want access to it.
+  proc = test['proc']
+  (stdout, stderr) = proc.communicate()
+
+  if test['aborted_at'] != 0:
+    FailTest(resultfile, test, "Compile timed out. Started %f ended %f." %
+             (test['started_at'], test['aborted_at']))
+    return
+
+  if test['expectations'] is None:
+    # This signals a compiler sanity check test. Fail iff compilation failed.
+    if proc.poll() == 0:
+      PassTest(resultfile, test)
+      return
+    else:
+      FailTest(resultfile, test, 'Sanity compile failed. Is compiler borked?',
+               stdout, stderr)
+      return
+  elif proc.poll() == 0:
+    # Handle failure due to successful compile.
+    FailTest(resultfile, test,
+             'Unexpected successful compilation.',
+             stdout, stderr)
+    return
+  else:
+    # Check the output has the right expectations.  If there are no
+    # expectations, then we just consider the output "matched" by default.
+    if len(test['expectations']) == 0:
+      PassTest(resultfile, test)
+      return
+
+    # Otherwise test against all expectations.
+    for regexp in test['expectations']:
+      if (regexp.search(stdout) is not None or
+          regexp.search(stderr) is not None):
+        PassTest(resultfile, test)
+        return
+    expectation_str = ', '.join(
+        ["r'%s'" % regexp.pattern for regexp in test['expectations']])
+    FailTest(resultfile, test,
+             'Expectations [%s] did not match output.' % expectation_str,
+             stdout, stderr)
+    return
+
+
+def CompleteAtLeastOneTest(resultfile, executing_tests):
+  """Blocks until at least one task is removed from executing_tests.
+
+  This function removes completed tests from executing_tests, logging failures
+  and output.  If no tests can be removed, it will enter a poll-loop until one
+  test finishes or times out.  On a timeout, this function is responsible for
+  terminating the process in the appropriate fashion.
+
+  Args:
+    executing_tests: A dict mapping a string containing the test name to the
+                     test dict return from StartTest().
+
+  Returns:
+    A tuple with a set of tests that have finished.

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

"tuple with a set" sounds like a set is involved, but none is.
(general comment: you use a comment style emphasizing the type of the variable
over its contents; it's almost like you expect the reader to be a C compiler ;))

[awong, 2011/09/09 01:01:43]

Yeah yeah...dynamic languages make me uncomfortable. :(

Fixed the comment.

+  """
+  finished_tests = []
+  while len(finished_tests) == 0:
+    # Select on the output pipes.
+    read_set = []
+    for test in executing_tests.values():
+      read_set.extend([test['proc'].stderr, test['proc'].stdout])
+    result = select.select(read_set, [], read_set, BUSY_LOOP_MAX_TIME_SEC)
+
+   # We timed out on all running tests. Assume this whole thing is hung.

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

indent

[awong, 2011/09/09 01:01:43]

deleted.

+    if result == ([],[],[]):
+      raise WatchdogException('Busy looping for too long. Aborting no compile '

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

s/no compile/no-compile/
(b/c otherwise the "no" binds to "Aborting" for me)

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

Where does WatchdogException come from?

[awong, 2011/09/09 01:01:43]

deleted.

[awong, 2011/09/09 01:01:43]

deleted

+                              'test.')
+
+    # Now attempt to process results.
+    now = time.time()
+    for test in executing_tests.values():
+      proc = test['proc']
+      if proc.poll() is not None:
+        test['finished_at'] = now
+        finished_tests.append(test)
+      elif test['terminate_timeout'] < now:
+        proc.terminate()
+        test['aborted_at'] = now
+      elif test['kill_timeout'] < now:
+        proc.kill()
+        test['aborted_at'] = now
+
+  return finished_tests
+
+
+def main():
+  if len(sys.argv) != 5:
+    print ('Usage: %s <parallelism> <sourcefile> <cflags> <resultfile>' %
+           sys.argv[0])
+    sys.exit(1)
+
+  # Force us into the "C" locale so the compiler doesn't localize its output.
+  # In particular, this stops gcc from using smart quotes when in english UTF-8
+  # locales.  This makes the expectation writing much easier.
+  os.environ['LC_ALL'] = 'C'
+
+  parallelism = int(sys.argv[1])
+  sourcefile_path = sys.argv[2]
+  cflags = sys.argv[3]
+  resultfile_path = sys.argv[4]
+
+  ValidateInput(parallelism, sourcefile_path, cflags, resultfile_path)
+
+  test_configs = ExtractTestConfigs(sourcefile_path)
+
+  resultfile = open(resultfile_path, 'w')
+  resultfile.write(RESULT_FILE_HEADER % sourcefile_path)
+
+  # Run the no-compile tests, but ensure we do not run more than |parallelism|
+  # tests at once.
+  executing_tests = {}
+  finished_tests = []
+  for config in test_configs:
+    # CompleteAtLeastOneTest blocks until at least one test finishes. Thus, this
+    # acts as a semaphore.  We cannot use threads + a real semaphore because
+    # subprocess forks, which can cause all sorts of hilarity with threads.
+    if len(executing_tests) >= parallelism:
+      just_finished = CompleteAtLeastOneTest(resultfile, executing_tests)
+      finished_tests.extend(just_finished)
+      for test in just_finished:
+        del executing_tests[test['name']]
+
+    if config['name'].startswith('DISABLED_'):
+      PassTest(resultfile, config)
+    else:
+      test = StartTest(sourcefile_path, cflags, config)
+      executing_tests[test['name']] = test

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

Any point in making assertions about uniqueness of test names?

[awong, 2011/09/09 01:01:43]

Done.

+
+  # If there are no more test to start, we still need to drain the running
+  # ones.
+  while len(executing_tests) > 0:
+    just_finished = CompleteAtLeastOneTest(resultfile, executing_tests)

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

Possible to avoid the duplication between l.446-449 and l.431-435?

[awong, 2011/09/09 01:01:43]

Not that I can think of.  But I took your other suggestion and reduced it down
to 1 line.

+    finished_tests.extend(just_finished)
+    for test in just_finished:
+      del executing_tests[test['name']]

[Ami GONE FROM CHROMIUM, 2011/09/08 18:30:20]

If this was in CompleteAtLeastOneTest it'd be only half the duplication to worry
about here...

[awong, 2011/09/09 01:01:43]

Done.

+
+  for test in finished_tests:
+    ProcessTestResult(resultfile, test)
+
+  resultfile.close()
+
+
+if __name__ == '__main__':
+  main()