[Bug c/115185] Missing "too long" warning when string-array size doesn't include NULL byte

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=115185

--- Comment #12 from GCC Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Martin Uecker <uecker@gcc.gnu.org>:

https://gcc.gnu.org/g:44c9403ed1833ae71a59e84f9e37af3182be0df5

commit r15-2026-g44c9403ed1833ae71a59e84f9e37af3182be0df5
Author: Alejandro Colomar <alx@kernel.org>
Date:   Sat Jun 29 15:10:43 2024 +0200

    c, objc: Add -Wunterminated-string-initialization

    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.

    Since Wc++-compat now includes this warning, the test has to be modified
    to expect the text of the new warning too, in <gcc.dg/Wcxx-compat-14.c>.

    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-ec66160cf413@gmail.com/T/

            PR c/115185

    gcc/c-family/ChangeLog:

            * c.opt: Add -Wunterminated-string-initialization.

    gcc/c/ChangeLog:

            * c-typeck.cc (digest_init): Separate warnings about character
            arrays being initialized as unterminated character sequences
            with string literals, from -Wc++-compat, into a new warning,
            -Wunterminated-string-initialization.

    gcc/ChangeLog:

            * doc/invoke.texi: Document the new
            -Wunterminated-string-initialization.

    gcc/testsuite/ChangeLog:

            * gcc.dg/Wcxx-compat-14.c: Adapt the test to match the new text
            of the warning, which doesn't say anything about C++ anymore.
            * gcc.dg/Wunterminated-string-initialization.c: New test.

    Acked-by: Doug McIlroy <douglas.mcilroy@dartmouth.edu>
    Acked-by: Mike Stump <mikestump@comcast.net>
    Reviewed-by: Sandra Loosemore <sloosemore@baylibre.com>
    Reviewed-by: Martin Uecker <uecker@tugraz.at>
    Signed-off-by: Alejandro Colomar <alx@kernel.org>
    Reviewed-by: Marek Polacek <polacek@redhat.com>