On Fri, 2023-03-24 at 14:39 +0100, Alejandro Colomar via Gcc-patches
wrote:
> Warn about the following:
>
> char s[3] = "foo";
>
> Initializing a char array with a string literal of the same length as
> the size of the array is usually a mistake. Rarely is the case where
> one wants to create a non-terminated character sequence from a string
> literal.
>
> In some cases, for writing faster code, one may want to use arrays
> instead of pointers, since that removes the need for storing an array
> of
> pointers apart from the strings themselves.
>
> char *log_levels[] = { "info", "warning", "err" };
> vs.
> char log_levels[][7] = { "info", "warning", "err" };
>
> This forces the programmer to specify a size, which might change if a
> new entry is later added. Having no way to enforce null termination
> is
> very dangerous, however, so it is useful to have a warning for this,
> so
> that the compiler can make sure that the programmer didn't make any
> mistakes. This warning catches the bug above, so that the programmer
> will be able to fix it and write:
>
> char log_levels[][8] = { "info", "warning", "err" };
>
> This warning already existed as part of -Wc++-compat, but this patch
> allows enabling it separately. It is also included in -Wextra, since
> it may not always be desired (when unterminated character sequences
> are
> wanted), but it's likely to be desired in most cases.
>
> Link:
> <https://lists.gnu.org/archive/html/groff/2022-11/msg00059.html>
> Link:
> <https://lists.gnu.org/archive/html/groff/2022-11/msg00063.html>
> Link:
> <https://inbox.sourceware.org/gcc/36da94eb-1cac-5ae8-7fea-ec66160cf41
> 3...@gmail.com/T/>
> Acked-by: Doug McIlroy <douglas.mcil...@dartmouth.edu>
> Cc: "G. Branden Robinson" <g.branden.robin...@gmail.com>
> Cc: Ralph Corderoy <ra...@inputplus.co.uk>
> Cc: Dave Kemper <saint.s...@gmail.com>
> Cc: Larry McVoy <l...@mcvoy.com>
> Cc: Andrew Pinski <pins...@gmail.com>
> Cc: Jonathan Wakely <jwakely....@gmail.com>
> Cc: Andrew Clayton <and...@digital-domain.net>
> Cc: Martin Uecker <muec...@gwdg.de>
> Signed-off-by: Alejandro Colomar <a...@kernel.org>
> ---
>
> Hi,
Hi Alex, thanks for the patch.
>
> I sent v1 to the wrong list. This time I've made sure to write to
> gcc-patches@.
Note that right now we're deep in bug-fixing/stabilization for GCC 13
(and trunk is still tracking that effort), so your patch might be more
suitable for GCC 14.
>
> v2 adds some draft of a test, as suggested by Martin. However, I
> don't
> know yet how to write those, so the test is just a draft. But I did
> test the feature, by compiling GCC and compiling some small program
> with
> it.
Unfortunately the answer to the question "how do I run just one
testcase in GCC's testsuite" is rather non-trivial; FWIW I've written
up some notes on working with the GCC testsuite here:
https://gcc-newbies-guide.readthedocs.io/en/latest/working-with-the-testsuite.html
Hope this is helpful
Dave
[...snip...]
