Re: [Mingw-users] libc bug report

[Benjamin R. <Ben...@ep...>]

Hi Anders,


> Subject: Re: [Mingw-users] libc bug report

Just to clarify, Mingw uses the MS runtime library, not GNU libc.
OTOH small parts of it, like the macro/inline versions of
fputc()/fgetc(), is also defined in the headers.

Anders Lind=E9n <mi...@ca...> writes:
> void dotheoperation()
> {
>   FILE *file;
>   int byte;
>
>   if ((file=3Dfopen("file.dat","r+b"))=3D=3DNULL)
>     throw 0;
>
>   for (int i=3D0; i<8; i++)
>     fgetc(file);
>
>   fputc(0x20,file);  // where does this come in the result file??????

You are probably just missing a call to fflush() (or fseek() or
fsetpos()) between fgetc() and fputc() here.  Without that the results
of switching from reading to writing on the same file are undefined
per the C language definition.  See the definition of fopen("r+b") in
your favorite C reference.

>   fseek(file,-6,SEEK_CUR); // results in offset 3, which is correct
>
>   fputc(0x21,file);
>   fputc(0x22,file);
>   fclose(file);
> }


benny