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Shrink the tz_offset size to 41. (#1110) 

When building with gcc TSan on, and in Debug mode, we see a warning
like:

benchmark/src/timers.cc: In function ‘std::string benchmark::LocalDateTimeString()’:
src/timers.cc:241:15: warning: ‘char* strncat(char*, const char*, size_t)’ output may be truncated copying 108 bytes from a string of length 127 [-Wstringop-truncation]
  241 |   std::strncat(storage, tz_offset, sizeof(storage) - timestamp_len - 1);
      |   ~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

While this is essentially a false positive (we never expect
the number of bytes in tz_offset to be too large), the compiler can't
actually tell that.  Shrink the size of tz_offset to a smaller, but still safe
size to eliminate this warning.

Signed-off-by: Chris Lalancette <clalancette@openrobotics.org>
This commit is contained in:
Chris Lalancette 2021-04-09 12:32:00 -04:00 committed by GitHub
parent f1deaf16b8
commit 07578d82e0
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1 changed files with 10 additions and 2 deletions
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src/timers.cc
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@ -190,8 +190,16 @@ std::string LocalDateTimeString() {
std::size_t timestamp_len;
long int offset_minutes;
char tz_offset_sign = '+';
// Long enough buffers to avoid format-overflow warnings
char tz_offset[128];
// tz_offset is set in one of three ways:
// * strftime with %z - This either returns empty or the ISO 8601 time. The maximum length an
// ISO 8601 string can be is 7 (e.g. -03:30, plus trailing zero).
// * snprintf with %c%02li:%02li - The maximum length is 41 (one for %c, up to 19 for %02li,
// one for :, up to 19 %02li, plus trailing zero).
// * A fixed string of "-00:00". The maximum length is 7 (-00:00, plus trailing zero).
//
// Thus, the maximum size this needs to be is 41.
char tz_offset[41];
// Long enough buffer to avoid format-overflow warnings
char storage[128];
#if defined(BENCHMARK_OS_WINDOWS)