lseek SEEK_SET fails on Windows

[Y-Less]

No idea why, but the function call returns 0 (which is correct), yet future writes continue from the old location not the new one. I had to change fseek to:

  return fseek((FILE *)params[1],params[2],whence);

And flength to:

  int fn=fileno((FILE*)params[1]);
  c=lseek(fn,0,SEEK_CUR); /* save the current position */
  l=lseek(fn,0,SEEK_END); /* return the file position at its end */
  fseek((FILE *)params[1],c,SEEK_SET);   /* restore the file pointer */

The latter uses a mix of lseek and fseek because all of one or the other failed in different ways.

[namazso]

Maybe this happens on a file bigger than 2 GB? windows has _lseeki64 for big files

[Y-Less]

The file I tested it with was 13 bytes:

bool:test_fseek()
{
	fremove("fseek.ini");
	new File:f = fopen("fseek.ini", io_write);
	if (!f)
	{
		print("FAIL: File didn't open\n");
		return false;
	}
	fwrite(f, "hello world");
	fseek(f, 0, seek_start);
	fwrite(f, "hi");
	if (flength(f) != 11)
	{
		print("FAIL: `flength` != 11\n");
		return false;
	}
	fwrite(f, "hello world");
	if (flength(f) != 13)
	{
		print("FAIL: `flength` != 13\n");
		return false;
	}
	fclose(f);
	return true;
}

[namazso]

Reading through POSIX and various documentations there doesn't seem to be any guarantee of relations between a fd and a FILE. Additionally, the C standard allows FILE to store position information. So I think the code is just simply wrong and built on top of incorrect assumptions.