Get rid of the !!()-constructs and use ret where available (or introduce it).
In some cases, there would be an "abort" on the first fshut-error, but we want
to close all files and report all warnings and then quit, not just the warning
for the first file.
This has been a known issue for a long time. Example:
printf "word" > /dev/full
wouldn't report there's not enough space on the device.
This is due to the fact that every libc has internal buffers
for stdout which store fragments of written data until they reach
a certain size or on some callback to flush them all at once to the
kernel.
You can force the libc to flush them with fflush(). In case flushing
fails, you can check the return value of fflush() and report an error.
However, previously, sbase didn't have such checks and without fflush(),
the libc silently flushes the buffers on exit without checking the errors.
No offense, but there's no way for the libc to report errors in the exit-
condition.
GNU coreutils solve this by having onexit-callbacks to handle the flushing
and report issues, but they have obvious deficiencies.
After long discussions on IRC, we came to the conclusion that checking the
return value of every io-function would be a bit too much, and having a
general-purpose fclose-wrapper would be the best way to go.
It turned out that fclose() alone is not enough to detect errors. The right
way to do it is to fflush() + check ferror on the fp and then to a fclose().
This is what fshut does and that's how it's done before each return.
The return value is obviously affected, reporting an error in case a flush
or close failed, but also when reading failed for some reason, the error-
state is caught.
the !!( ... + ...) construction is used to call all functions inside the
brackets and not "terminating" on the first.
We want errors to be reported, but there's no reason to stop flushing buffers
when one other file buffer has issues.
Obviously, functionales come before the flush and ret-logic comes after to
prevent early exits as well without reporting warnings if there are any.
One more advantage of fshut() is that it is even able to report errors
on obscure NFS-setups which the other coreutils are unable to detect,
because they only check the return-value of fflush() and fclose(),
not ferror() as well.
1) Remove the return-value-enum, which is not necessary for a simple
program like this.
2) Don't disallow both l and s to be specified. This is undefined
behaviour defined by POSIX, so we don't start demanding things
from the user.
3) Replace exit() with return (we are in main).
4) Refactor main loop to never return in the loop, but actually
set the same-value and break, which increases readability.
5) Remove the final fclose()'s. The OS will take care of them, no
need to become cleansy here.
6) Use idiomatic return-value using same. This concludes the
increase of readability in the main-loop.
The algorithm had some areas which had potential for improvement.
This should make cmp(1) faster.
There have been changes to behaviour as well:
1) If argv[0] and argv[1] are the same, cmp(1) returns Same.
2) POSIX specifies the format of the difference-message to be:
"%s %s differ: char %d, line %d\n", file1, file2,
<byte number>, <line number>
However, as cmp(1) operates on bytes, not characters, I changed
it to
"%s %s differ: byte %d, line %d\n", file1, file2,
<byte number>, <line number>
This is one example where the standard just keeps the old format
for backwards-compatibility. As this is harmful, this change
makes sense in the sense of consistentcy (and because we take
the difference of char and byte very seriously in sbase, as
opposed to GNU coreutils).
The manpage has been annotated, reflecting the second change, and
sections shortened where possible.
Thus I marked cmp(1) as finished in README.
It actually makes the binaries smaller, the code easier to read
(gems like "val == true", "val == false" are gone) and actually
predictable in the sense of that we actually know what we're
working with (one bitwise operator was quite adventurous and
should now be fixed).
This is also more consistent with the other suckless projects
around which don't use boolean types.
