Dear all, I have a program which reads concurrently multiple files using the C I/O library. I have encountered a problem, _ftelli64 randomly reports an incorrect position, with a mismatch of a few bytes. The bug disappears if any of these changes is done:
- ftell is used instead of _ftelli64 (but no more large file support) - std::ifstream is used instead of C functions (but I need _wfopen for unicode file names) - files are not read concurrently (reading threads set to 1) I have reproduced this in the attached MCVE. It does create 8 files approximately 3MB large, and reads them concurrently in 8 threads by 65544 byte blocks. It compares the value returned by fread() and the difference between _ftelli64 calls before and after fread(). It prints the mismatches. Typical output is : Error 2.dat / ftell before 3080570 / fread returned 65544 / ftell after 3146112 / mismatch -2 Error 6.dat / ftell before 3080569 / fread returned 65544 / ftell after 3146112 / mismatch -1 Error 4.dat / ftell before 65544 / fread returned 65544 / ftell after 131089 / mismatch 1 Error 5.dat / ftell before 0 / fread returned 65544 / ftell after 65543 / mismatch -1 Error 5.dat / ftell before 65543 / fread returned 65544 / ftell after 131088 / mismatch 1 Error 4.dat / ftell before 2162953 / fread returned 65544 / ftell after 2228498 / mismatch 1 Error 5.dat / ftell before 2162952 / fread returned 65544 / ftell after 2228497 / mismatch 1 Error 4.dat / ftell before 3080570 / fread returned 65544 / ftell after 3146112 / mismatch -2 Error 5.dat / ftell before 3080569 / fread returned 65544 / ftell after 3146112 / mismatch -1 Is this a bug from windows or from MinGW C library? Thanks! ------------------------------------------------------------------------------ Check out the vibrant tech community on one of the world's most engaging tech sites, Slashdot.org! http://sdm.link/slashdot _______________________________________________ Mingw-w64-public mailing list Mingw-w64-public@lists.sourceforge.net https://lists.sourceforge.net/lists/listinfo/mingw-w64-public
