How to make Google Test detect the number of threads on Linux?

Question

When running the death tests written using Google Test framework the following warning is produced for each of the tests:

[WARNING] .../gtest-death-test.cc:789:: Death tests use fork(), which is unsafe
particularly in a threaded context. For this test, Google Test couldn't detect
the number of threads.

Is there a way to make Google Test detect the number of threads on Linux?

One would think that the clever people of google would know how to do that if it was easy? ;) — Mats Petersson, Dec 27 '12 at 23:35
@MatsPetersson: Well, sometimes there are too many easy things to do. — vitaut, Dec 28 '12 at 00:59

vitaut · Accepted Answer · 2015-11-14T02:28:23.940

11

I've looked at the source code and it turned out that detection of the number of threads is implemented only for MacOS X and QNX, but not on Linux or other platforms. So I implemented missing functionality myself by counting the number of entries in /proc/self/task. Since it might be useful for others I'm posting it here (I've also sent it to the Google Test group):

size_t GetThreadCount() {
  size_t thread_count = 0;
  if (DIR *dir = opendir("/proc/self/task")) {
    while (dirent *entry = readdir(dir)) {
      if (strcmp(entry->d_name, ".") != 0 && strcmp(entry->d_name, "..") != 0)
        ++thread_count;
    }
    closedir(dir);
  }
  return thread_count;
}

As of 25 August 2015, Google Test implements GetThreadCount on Linux:

size_t GetThreadCount() {
  const string filename =
      (Message() << "/proc/" << getpid() << "/stat").GetString();
  return ReadProcFileField<int>(filename, 19);
}

edited Nov 14 '15 at 02:28

answered Dec 28 '12 at 00:57

vitaut

49,672
25
199
336

Slight optimisation, since all the entries would be numbers, you could just do `if (entry->d_name[0] != '.') ... ` instead of your two calls to strcmp... I'm sure it doesn't matter really... – Mats Petersson Dec 28 '12 at 01:03
1

I do like your solution, by the way. – Mats Petersson Dec 28 '12 at 01:05
@MatsPetersson: Thanks. You are right about the performance, but it is only for death tests which are slowish anyway. – vitaut Dec 28 '12 at 01:09
1

Here's a link to the gtest issue and patch (tested on Ubuntu 14.04 with gcc 4.9): https://code.google.com/p/googletest/issues/detail?id=464&q=couldn%27t%20detect&colspec=ID%20Type%20Status%20Priority%20Stars%20Owner%20Summary – Kurt Aug 08 '14 at 16:15

score 6 · Answer 2 · edited Jan 14 '16 at 08:08

6

If you don't care much about the test execution time, a convenient alternative is to use:

::testing::FLAGS_gtest_death_test_style = "threadsafe";

More details here.

edited Jan 14 '16 at 08:08

psur

4,400
26
36

answered Mar 20 '14 at 23:36

Paul Baltescu

2,095
4
25
30

1

I do care about test execution time, but thanks for the answer. Didn't know about this option. – vitaut Feb 18 '15 at 14:02
It can be also passed as command line argument: `--gtest_death_test_style=threadsafe` – psur Jan 14 '16 at 08:06

How to make Google Test detect the number of threads on Linux?

2 Answers2