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Converting a time string to std :: time_t using std :: get_time: incorrect result

I am trying to sort photos in chronological order. Therefore, I extract time as a string from EXIF ​​data, which I then convert to std::time_t. However, sometimes I get the wrong result. I reduced the problem to this minimal example. It has three time lines: one second:

#include <vector>
#include <string>
#include <iostream>
#include <ctime>
#include <iomanip>
#include <sstream>

int main()
{
  std::vector<std::string> vec;

  vec.push_back("2016:07:30 09:27:06");
  vec.push_back("2016:07:30 09:27:07");
  vec.push_back("2016:07:30 09:27:08");

  for ( auto & i : vec )
  {
    struct std::tm tm;
    std::istringstream iss;
    iss.str(i);
    iss >> std::get_time(&tm,"%Y:%m:%d %H:%M:%S");

    std::time_t time = mktime(&tm);

    std::cout << i << " time = " << time << std::endl;
  }
}

Compiled with clang++ -std=c++14 test.cpp.

Exit:

2016:07:30 09:27:06 time = 1469867226
2016:07:30 09:27:07 time = 1469863627
2016:07:30 09:27:08 time = 1469863628

What is clearly wrong, they should be 1separated from each other, which is true only for the last two?

Edit

Since an error appears in clang std::get_time(s std::put_time), here is my version information:

$ clang --version
Apple LLVM version 8.1.0 (clang-802.0.42)
Target: x86_64-apple-darwin16.7.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin
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2 answers

, . , clang. Bugzilla LLVM, . , .

, std::sscanf() std::tm. i. . std::get_time() std::sscanf() ideone. , .

%d:%d:%d %d:%d:%d . %4d:%2d:%2d %2d:%2d:%2d, , % d.

:

2016:07:30 09:27:06 | sscanf() time =        1469870826
2016:07:30 09:27:06 | std::get_time() time = 1469870826
2016:07:30 09:27:07 | sscanf() time =        1469870827
2016:07:30 09:27:07 | std::get_time() time = 1469870827
2016:07:30 09:27:08 | sscanf() time =        1469870828
2016:07:30 09:27:08 | std::get_time() time = 1469870828

:

#include <vector>
#include <string>
#include <iostream>
#include <ctime>
#include <iomanip>
#include <sstream>
#include <cstring>

int main()
{
   std::vector<std::string> vec;

   vec.push_back("2016:07:30 09:27:06");
   vec.push_back("2016:07:30 09:27:07");
   vec.push_back("2016:07:30 09:27:08");

   for (auto & i : vec)
   {
      struct std::tm tm;

      /* std::sscanf() method: */
      std::memset(&tm, 0, sizeof(tm));
      if (6 != std::sscanf(i.c_str(), "%d:%d:%d %d:%d:%d",
                           &tm.tm_year, &tm.tm_mon, &tm.tm_mday,
                           &tm.tm_hour, &tm.tm_min, &tm.tm_sec))
      {
         return -1;
      }

      /* correct the numbers according to:
       * see: http://en.cppreference.com/w/cpp/chrono/c/tm */
      --tm.tm_mon;
      tm.tm_year -= 1900;
      /* mktime determines if Daylight Saving Time was in effect
       * see: http://en.cppreference.com/w/cpp/chrono/c/mktime */
      tm.tm_isdst = -1;

      std::time_t time = std::mktime(&tm);

      std::cout << i << " | sscanf() time =        " << time << std::endl;

      /************************************************************/

      /* std::get_time() method: */
      std::istringstream iss;
      iss.str(i);
      iss >> std::get_time(&tm, "%Y:%m:%d %H:%M:%S");

      time = std::mktime(&tm);

      std::cout << i << " | std::get_time() time = " << time << std::endl;
   }
}

tm_mon, 0. tm_year - 1900 . . std::tm .

, tm_isdst -1, std::mktime() , .

std::time_t timestamp Linux std::string : %Y:%m:%d %H:%M:%S std::strftime() std:: localtime(). ideone.

:

time = 1469870826 | 2016:07:30 09:27:06

:

#include <vector>
#include <string>
#include <iostream>
#include <ctime>

int main()
{
   char buff[20];
   time_t timestamp = 1469870826;
   std::strftime(buff, sizeof(buff), "%Y:%m:%d %H:%M:%S", std::localtime(&timestamp));
   std::string timeStr(buff);

   std::cout << "time = " << timestamp << " | " << timeStr;
}
+2

, , . . - , . , , "". - include:

#include "date.h"
#include <vector>
#include <string>
#include <iostream>
#include <sstream>

int main()
{
  std::vector<std::string> vec;

  vec.push_back("2016:07:30 09:27:06");
  vec.push_back("2016:07:30 09:27:07");
  vec.push_back("2016:07:30 09:27:08");

  for ( auto & i : vec )
  {
    date::sys_seconds tm;
    std::istringstream iss{i};
    iss >> date::parse("%Y:%m:%d %H:%M:%S", tm);

    std::cout << i << " time = " << tm.time_since_epoch().count() << std::endl;
    std::cout << date::format("%Y:%m:%d %H:%M:%S\n", tm);
  }
}

:

2016:07:30 09:27:06 time = 1469870826
2016:07:30 09:27:06
2016:07:30 09:27:07 time = 1469870827
2016:07:30 09:27:07
2016:07:30 09:27:08 time = 1469870828
2016:07:30 09:27:08
+3

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