Commit Graph

11 Commits

Author SHA1 Message Date
FRIGN 11e2d472bf Add *fshut() functions to properly flush file streams
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.
2015-04-05 09:13:56 +01:00
FRIGN 9144d51594 Check getline()-return-values properly
It's not useful when 0 is returned anyway, so be sure that we have a
string with length > 0, this also solves some indexing-gotchas like
"len - 1" and so on.
Also, add checked getline()'s whenever it has been forgotten and
clean up the error-messages.
2015-03-27 14:49:48 +01:00
FRIGN 93fd817536 Add estrlcat() and estrlcpy()
It has become a common idiom in sbase to check strlcat() and strlcpy()
using

if (strl{cat, cpy}(dst, src, siz) >= siz)
        eprintf("path too long\n");

However, this was not carried out consistently and to this very day,
some tools employed unchecked calls to these functions, effectively
allowing silent truncations to happen, which in turn may lead to
security issues.
To finally put an end to this, the e*-functions detect truncation
automatically and the caller can lean back and enjoy coding without
trouble. :)
2015-03-17 11:24:49 +01:00
FRIGN 0c2f19c210 Audit logger(1)
1) Update manpage to current style
2) Line spacing
3) Local variable grouping
4) check for getline >= 0 instead of != -1
5) error message cleanup
2015-03-07 00:10:22 +01:00
sin 71de7813c0 Include strings.h for strcasecmp()
Fixes another build error on NetBSD.
2015-02-20 16:00:58 +00:00
Hiltjo Posthuma 31f0624f3d code-style: minor cleanup and nitpicking 2015-02-20 13:29:38 +01:00
FRIGN 31572c8b0e Clean up #includes 2015-02-14 21:12:23 +01:00
sin 7e8fcc1f03 logger: Don't bother freeing buf
There are many more instances of this pattern.
2014-12-16 20:14:40 +00:00
sin 296af80dba Factor out table walk into a separate function 2014-12-09 15:51:21 +00:00
sin 95c9b4b255 Staticise functions in logger(1) 2014-12-04 11:46:11 +00:00
sin 5d1e46fefa Implement POSIX 2008 compliant logger(1) 2014-12-04 11:36:40 +00:00