date_time: valgrind warnings via strings_from_facet.hpp

[Lars Immisch <lars.immisch@…>]

On Ubuntu, with GNU libc6 (2.7-10ubuntu7), and a program that uses boost::date_time::time_input_facet< boost::posix_time::ptime,char> valgrind generates a warning:

==11026== Conditional jump or move depends on uninitialised value(s)
==11026==    at 0x467C04B: __strftime_internal (strftime_l.c:574)
==11026==    by 0x467DD4F: strftime_l (strftime_l.c:490)
==11026==    by 0x456B420: std::__timepunct<char>::_M_put(char*, unsigned int, char const*, tm const*) const (in /usr/lib/libstdc++.so.6.0.13)
==11026==    by 0x452BB4C: std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::do_put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, tm const*, char, char) const (in /usr/lib/libstdc++.so.6.0.13)
==11026==    by 0x452B0CF: std::time_put<char, std::ostreambuf_iterator<char, std::char_traits<char> > >::put(std::ostreambuf_iterator<char, std::char_traits<char> >, std::ios_base&, char, tm const*, char const*, char const*) const (in /usr/lib/libstdc++.so.6.0.13)
==11026==    by 0x8430C83: std::vector<std::basic_string<char, std::char_traits<char>, std::allocator<char> >, std::allocator<std::basic_string<char, std::char_traits<char>, std::allocator<char> > > > boost::date_time::gather_month_strings<char>(std::locale const&, bool) (strings_from_facet.hpp:58)
==11026==    by 0x84310D9: boost::date_time::format_date_parser<boost::gregorian::date, char>::format_date_parser(std::string const&, std::locale const&) (format_date_parser.hpp:188)
==11026==    by 0x8431435: boost::date_time::date_input_facet<boost::gregorian::date, char, std::istreambuf_iterator<char, std::char_traits<char> > >::date_input_facet(std::string const&, unsigned int) (date_facet.hpp:462)
==11026==    by 0x84315E0: boost::date_time::time_input_facet<boost::posix_time::ptime, char, std::istreambuf_iterator<char, std::char_traits<char> > >::time_input_facet(std::string const&, unsigned int) (time_facet.hpp:696)

The actual problem is in GNU libc6, strftime_l.c:574, which computes a 12 hour clock in __strftime_internal regardless of the format string:

  if (hour12 > 12)
    hour12 -= 12;
  else
    if (hour12 == 0)
      hour12 = 12;

The attached patch works around the warning by using an initialised struct tm in two places:

tm tm_value = { 0, 0, 0, 0, 0, 0, 0, 0, 0 };

We'd very much appreciate if the attached patch was accepted, even if it is only cosmetic.

[Lars Immisch <lars.immisch@…>]

Patch for uninitialized struct tm in strings_from_facet.hpp

[Marshall Clow]

This patch has the same problem as was observed in #3477 - on some platforms, struct tm has different numbers of elements. Is

tm tm_value = {};

sufficient to fix this problem?

[Lars Immisch <lars.immisch@…>]

Yes, that fixes the problem.

(Thanks, clever! I didn't think of that)

[Marshall Clow]

(In [70780]) Applied modified patch - Refs #4798

[Marshall Clow]

(In [70983]) Merge date/time fixes to release. Fixes #4798