On Feb 6, 2024, at 2:45 AM, Alejandro Colomar <a...@kernel.org> wrote:
>
> Warn about the following:
>
> char s[3] = "foo";
No ObjC specific impact here, so no need for ObjC review.
As a member of the peanut gallery, I like the patch.
Joseph, this is been submitted 5 times over the past year. Any thoughts?
> 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-ec66160cf...@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>
> Cc: David Malcolm <dmalc...@redhat.com>
> Signed-off-by: Alejandro Colomar <a...@kernel.org>
> ---
>
> v5:
>
> - Fix existing C++-compat tests. [reported by <ci_not...@linaro.org>]
>
>
> gcc/c-family/c.opt | 4 ++++
> gcc/c/c-typeck.cc | 6 +++---
> gcc/testsuite/gcc.dg/Wcxx-compat-14.c | 2 +-
> gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c | 6 ++++++
> 4 files changed, 14 insertions(+), 4 deletions(-)
> create mode 100644 gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c
>
> diff --git a/gcc/c-family/c.opt b/gcc/c-family/c.opt
> index 44b9c862c14..e8f6b836836 100644
> --- a/gcc/c-family/c.opt
> +++ b/gcc/c-family/c.opt
> @@ -1407,6 +1407,10 @@ Wunsuffixed-float-constants
> C ObjC Var(warn_unsuffixed_float_constants) Warning
> Warn about unsuffixed float constants.
>
> +Wunterminated-string-initialization
> +C ObjC Var(warn_unterminated_string_initialization) Warning LangEnabledBy(C
> ObjC,Wextra || Wc++-compat)
> +Warn about character arrays initialized as unterminated character sequences
> by a string literal.
> +
> Wunused
> C ObjC C++ ObjC++ LangEnabledBy(C ObjC C++ ObjC++,Wall)
> ; documented in common.opt
> diff --git a/gcc/c/c-typeck.cc b/gcc/c/c-typeck.cc
> index e55e887da14..7df9de819ed 100644
> --- a/gcc/c/c-typeck.cc
> +++ b/gcc/c/c-typeck.cc
> @@ -8399,11 +8399,11 @@ digest_init (location_t init_loc, tree type, tree
> init, tree origtype,
> pedwarn_init (init_loc, 0,
> ("initializer-string for array of %qT "
> "is too long"), typ1);
> - else if (warn_cxx_compat
> + else if (warn_unterminated_string_initialization
> && compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
> - warning_at (init_loc, OPT_Wc___compat,
> + warning_at (init_loc, OPT_Wunterminated_string_initialization,
> ("initializer-string for array of %qT "
> - "is too long for C++"), typ1);
> + "is too long"), typ1);
> if (compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
> {
> unsigned HOST_WIDE_INT size
> diff --git a/gcc/testsuite/gcc.dg/Wcxx-compat-14.c
> b/gcc/testsuite/gcc.dg/Wcxx-compat-14.c
> index 23783711be6..6df0ee197cc 100644
> --- a/gcc/testsuite/gcc.dg/Wcxx-compat-14.c
> +++ b/gcc/testsuite/gcc.dg/Wcxx-compat-14.c
> @@ -2,5 +2,5 @@
> /* { dg-options "-Wc++-compat" } */
>
> char a1[] = "a";
> -char a2[1] = "a"; /* { dg-warning "C\[+\]\[+\]" } */
> +char a2[1] = "a"; /* { dg-warning "initializer-string for array of 'char'
> is too long" } */
> char a3[2] = "a";
> diff --git a/gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c
> b/gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c
> new file mode 100644
> index 00000000000..13d5dbc6640
> --- /dev/null
> +++ b/gcc/testsuite/gcc.dg/Wunterminated-string-initialization.c
> @@ -0,0 +1,6 @@
> +/* { dg-do compile } */
> +/* { dg-options "-Wunterminated-string-initialization" } */
> +
> +char a1[] = "a";
> +char a2[1] = "a"; /* { dg-warning "initializer-string for array of 'char'
> is too long" } */
> +char a3[2] = "a";
