Subject: Re: New compile warnings...
halmurray at sonic.net
Wed Nov 17 07:14:12 UTC 2021
> It compiles fine, until I add this:
> export CFLAGS="-Wvla -fanalyzer"
Apologies for the noise and/or not paying attention sooner and thanks for
opening up this can of worms.
In case anybody else hasn't looked in the man page yet...
Warn if a variable-length array is used in the code. -Wno-vla
prevents the -Wpedantic warning of the variable-length array.
This option enables an static analysis of program flow which looks
for "interesting" interprocedural paths through the code, and
issues warnings for problems found on them.
I haven't seen any vla warnings yet. Have you?
The ones that I now understand are possible derefrencing NULLs. I find it a
bit hard to understand their big complicated error message, but it's easy to
figure things out now that I know what to look for.
I fixed 2 actual bugs - not checking malloc.
In 2 other cases, I added ugly hack code to keep the compiler happy.
You may get a few more if you run tests/option-tester.sh
Older/different compilers also make more warnings. This pair is fairly common
for my collection of toys:
../../ntpd/ntp_leapsec.c:962:5: warning: leak of FILE "farg" [CWE-775]
../../tests/unity/unity_memory.c:104:5: warning: leak of "guard" [CWE-401]
There are a couple of warnings from the parser area. I haven't investigated.
Is there a way to tell the compiler that X isn't NULL? Or similar for other
warnings from fanalyze?
Consider this example:
int mon_get_oldest_age(l_fp now)
mon_entry * oldest;
if (mon_data.mru_entries == 0)
oldest = TAIL_DLIST(mon_data.mon_mru_list, mru);
now -= oldest->last;
It's complaining because oldest might be NULL. TAIL_DLIST is part of a set of
macros for handling doubly linked lists. The mru_entries test checks for the
list being empty so if we get to using oldest, it won't be NULL.
I'd be happy to add a "comment" to tell the compiler not to complain.
In two cases, I added code to actually do a NULL check. On one hand, that
won't cost much. On the other hand, this one gets called for every packet and
I hate adding dumb code to the main path. It's also clutter. The comment is
bigger than the code.
These are my opinions. I hate spam.
More information about the devel