Hi David, Sorry for the half-year delay! I have some update. :)
On Fri, Mar 24, 2023 at 10:53:22AM -0400, David Malcolm wrote:
> 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...]
>
I ran the tests, and get some unexpected failure. I used dg-warning,
but maybe I used it wrong? Here's the output:
```
output is:
/home/alx/src/gnu/gcc/wustr/gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c:5:14:
warning: initializer-string for array of 'char' is too long
[-Wunterminated-string-initi
alization]
FAIL: gcc.dg/Wunterminated-string-initialization.c (test for warnings, line 5)
```
And here's the test:
```
/* { dg-do compile } */
/* { dg-options "-Wunterminated-string-initialization" } */
char a1[] = "a";
char a2[1] = "a"; /* { dg-warning "unterminated char sequence" } */
char a3[2] = "a";
```
Why isn't it expecting the warning?
Thanks,
Alex
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