Re: fseek and ftell with large files on Windows

[Bruno Haible]

Markus Mützel wrote:
> If the unit test passes with it, it might be passing erroneously.

No: Before making the fixes and adding the unit test, I verified that without
the fixes, the unit test failed. In other words, the unit test is able
to detect the bugs we are interested in.

> >   - Apparently the mingw fseeko already supports the 64-bit argument 
> fine.
> 
> 
> "fseeko" has the following prototype in mingw-w64:
> https://sourceforge.net/p/mingw-w64/code/HEAD/tree/trunk/mingw-w64-crt/stdio/fseeko32.c
> int fseeko(FILE* stream, _off_t offset, int whence)
> 
> The offset is of type "_off_t". That type is defined like this in mingw-w64:
> https://sourceforge.net/p/mingw-w64/code/HEAD/tree/trunk/mingw-w64-headers/crt/_mingw_off_t.h
>   typedef long _off_t;
> 
> "long" is a 32-bit integer on Windows. So, the "fseeko" function from 
> mingw-w64 shouldn't work for large files.
> 
> Does that make sense?

No. You missed the facts that
  - the Gnulib 'largefile' module defines _FILE_OFFSET_BITS to 64 on mingw,
  - mingw-w64-headers/crt/stdio.h thus does a
    #define fseeko fseeko64
  - fseeko64 is defined in mingw-w64-crt/stdio/fseeko64.c and takes a 64-bit
    argument.

Bruno