Re: nstrftime.c fails to build due to memset overflow

[Paul Eggert]

On 5/18/23 14:50, Bruno Haible wrote:
> But when "gcc -Wall" reports 10 warnings to me, and I don't notice
> that one of them is an actual bug because I mentally discard all of
> them

If you're using -O0, then in my experience it's a mistake to also use 
--enable-gcc-warnings, as the combination generates too many false 
positives. We shouldn't waste time worrying about them, any more than we 
waste time worrying about the false positives generated by 'clang -O2' 
and --enable-gcc-warnings.

Especially we should avoid pacifing GCC by adding things like 'IF_LINT 
(= 0)', without a really good reason (such as a compiler bug report that 
we've filed). The IF_LINT can cause 'gcc -O2' (the typical case) to 
generate false negatives, and also it can cause GCC to generate 
different code for non-debug builds. Both of these are problematic, and 
we should not add 'IF_LINT (= 0)' merely to pacify 'gcc -O0'.

While I'm on the topic, we should also not worry about other 
lower-priority platforms, such as 'gcc -m32' on x86-64. Each such 
invocation can generate a boatload of false positives, and in my 
experience fixing them is more trouble than it's worth. Of course if you 
try it on a new platform and find real bugs, that's another thing - but 
my experience with running 'gcc -m32' (after a clean 'gcc -m64' build) 
is pretty negative.


PS. As it happens, I gave a lecture today on static checking of 
low-level code, with one topic being GCC's warning diagnostics and their 
limitations, so this stuff is fairly fresh in my mind.