On 4/15/2013 02:50, Hin-Tak Leung wrote:
--- On Sun, 14/4/13, Vincent Povirk madewokherd@gmail.com wrote:
Well, here's a simple thing you can check: Does your zlib dll link to _lseek or _lseeki64? The first one uses a 32-bit offset. Wine's implementation (http://source.winehq.org/source/dlls/msvcrt/file.c#L1090) expands that to 64-bit and later truncates the file offset to 32-bit. For a file larger than 2 GB, that could account for the large negative value you're seeing.
And since this would only matter in cases where zlib uses lseek (the first time through I guess it wouldn't, as it has to read the whole everything up to the offset you give at least once) and is at least 2 GB into the file, that might also explain why it doesn't fail initially.
But without really digging into the zlib code, all I can do it speculate.
I should probably also check coapp's build of zlib sometime.
It is not a dll - as you suggested and I already wrote, due to past experience of other's packaging of slightly outdated, it is being built against a private *source* copy of the latest zlib.
Also the bogus offset is not large negative but large (larger than 2^32) positive.
Here is an example of the debug output under wine:
set_filepos failed at 34307 returning 134127533721091 Re-opening to re-try Retry successful set_filepos failed at 96919 returning 146686018157207 Re-opening to re-try Retry successful set_filepos failed at 128254 returning 12103217968382 Re-opening to re-try Retry successful ...
This is generated by this code snipplet which is called inside a loop, all wrapped in the c++ class:
off_t offset = gzseek(gzvcf_in, filepos, SEEK_SET); if (offset != filepos) { //implicitly converted to off_t by template streamoff() LOG.printLOG("set_filepos failed at " + LOG.streampos2str(filepos) + " returning " + LOG.off_t2str(offset) + "\n"); LOG.printLOG("Re-opening to re-try\n"); close(); open(); off_t offset1 = gzseek(gzvcf_in, filepos, SEEK_SET); if (offset1 == filepos) LOG.printLOG("Retry successful\n"); else LOG.error("Retry failed\n"); // this also aborts }
This code runs silently on linux i.e. the "if (offset != filepos)" condition is not triggered.
For windows build you'll need to define _WIN32, so _lseeki64 is used by zlib. After this done you could play with native msvcrt to see if it helps, and after that +relay will tell you everything.