"Dana How" <danahow@xxxxxxxxx> writes:
> Concerning SEEK_SET,
> you are correct: my unistd.h #define's SEEK_SET to 0.
My understanding of the history is back when there was seek()
but not lseek() nor SEEK_X macros, everybody passed bare
integers and it was quite well established that 0 meant what
SEEK_SET means now, so I would be quite surprised if there is
_any_ platform that defines SEEK_SET to anything but zero.
Having said that, I wonder if this kind of thing can be caught
with sparse. We should be able to express (or perhaps sparse
could have a built-in rule that says) something like "although
the standard says the third parameter to lseek() can be any
integer, you should not use anything but SEEK_X preprocessor
macros; also SEEK_X preprocessor macros, although they are
typically just "#define"s of small integer literals, can never
appear anywhere other than the third parameter as seek() and
lseek()". I realize that there needs some data-flow analysis to
allow a code like this, though:
int move_to(int fd, ofs_t offset, int relative)
{
int whence = SEEK_SET;
if (relative) {
whence = SEEK_CUR;
offset += relative;
}
return lseek(fd, offset, whence) != (off_t)-1;
}
> But if someone edits this, the arg order might remain.
Very true, and that is why I said I am going to take the patch.
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