From 8b4e43e768f3f49513f6f32f20ecb6478c1ad840 Mon Sep 17 00:00:00 2001 From: Guido van Rossum Date: Mon, 10 Sep 2001 20:43:35 +0000 Subject: [PATCH] _portable_fseek(): Subtlety on Windows: if we change test_largefile.py to use a file > 4GB, it still fails. A debug session suggests this is because fseek(fp, 0, 2) refuses to seek to the end of the file when the file is > 4GB, because it uses the SetFilePointer() in 32-bit mode. But it only fails when we seek relative to the end of the file, because in the other seek modes only calls to fgetpos() and fsetpos() are made, which use Get/SetFilePointer() in 64-bit mode. Solution: #ifdef MS_WInDOWS, replace the call to fseek(fp, ...) with a call to _lseeki64(fileno(fp), ...). Make sure to call fflush(fp) first. (XXX Could also replace the entire branch with a call to _lseeki64(). Would that be more efficient? Certainly less generated code.) (XXX This needs more testing. I can't actually test that it works for files >4GB on my Win98 machine, because the filesystem here won't let me create files >=4GB at all. Tim should test this on his Win2K machine.) --- Objects/fileobject.c | 6 ++++++ 1 file changed, 6 insertions(+) diff --git a/Objects/fileobject.c b/Objects/fileobject.c index 5909e99f47f..c8e3ae4ad80 100644 --- a/Objects/fileobject.c +++ b/Objects/fileobject.c @@ -239,8 +239,14 @@ _portable_fseek(FILE *fp, Py_off_t offset, int whence) fpos_t pos; switch (whence) { case SEEK_END: +#ifdef MS_WINDOWS + fflush(fp); + if (_lseeki64(fileno(fp), 0, 2) == -1) + return -1; +#else if (fseek(fp, 0, SEEK_END) != 0) return -1; +#endif /* fall through */ case SEEK_CUR: if (fgetpos(fp, &pos) != 0)