On Sun, Nov 13, 2022 at 1:57 PM Alejandro Colomar via Gcc
<gcc@gcc.gnu.org> wrote:
>
> Hi!
>
> I'd like to get warnings if I write the following code:
>
> char foo[3] = "foo";
This should be easy to add as it is already part of the -Wc++-compat
option as for C++ it is invalid code.
<source>:2:19: warning: initializer-string for array of 'char' is too long
2 | char two[2] = "foo"; // 'f' 'o'
| ^~~~~
<source>:3:19: warning: initializer-string for array of 'char' is too
long for C++ [-Wc++-compat]
3 | char three[3] = "foo"; // 'f' 'o' 'o'
| ^~~~~
... (for your more complex case [though I needed to modify one of the
strings to exactly 8]
<source>:5:7: warning: initializer-string for array of 'char' is too
long for C++ [-Wc++-compat]
5 | "01234567",
| ^~~~~~~~~~
else if (warn_cxx_compat
&& compare_tree_int (TYPE_SIZE_UNIT (type), len) < 0)
warning_at (init_loc, OPT_Wc___compat,
("initializer-string for array of %qT "
"is too long for C++"), typ1);
That is the current code which does this warning even so it is just a
matter of adding an option to c-family/c.opt and then having
c++-compat enable it and using that new option here.
Thanks,
Andrew Pinski
>
> It's hard to keep track of sizes to make sure that the string literals always
> initialize to terminated strings. It seems something that should be easy to
> implement in the compiler.
>
> A morecomplex case where it's harder to keep track of sizes is:
>
> static const char log_levels[][8] = {
> "alert",
> "error",
> "warn",
> "notice",
> "info",
> "debug",
> };
>
> Here, 8 works now (and 7 too, but for aligmnent reasons I chose 8). If
> tomorrow
> we add or change an entry, It'll be hard to keep it safe. Such a warning
> would
> help a lot.
>
>
> An example program is:
>
> $ cat str.c
> char two[2] = "foo"; // 'f' 'o'
> char three[3] = "foo"; // 'f' 'o' 'o'
> char four[4] = "foo"; // 'f' 'o' 'o' '\0'
> char five[5] = "foo"; // 'f' 'o' 'o' '\0' '\0'
> char implicit[] = "foo"; // 'f' 'o' 'o' '\0'
>
> $ cc -Wall -Wextra str.c
> str.c:1:19: warning: initializer-string for array of ‘char’ is too long
> 1 | char two[2] = "foo"; // 'f' 'o'
> | ^~~~~
> /usr/bin/ld:
> /usr/lib/gcc/x86_64-linux-gnu/12/../../../x86_64-linux-gnu/Scrt1.o:
> in function `_start':
> (.text+0x17): undefined reference to `main'
> collect2: error: ld returned 1 exit status
>
>
> Here, I'd like that with the new warning, 'three' would also get warned.
>
> Cheers,
>
> Alex
> --
> <http://www.alejandro-colomar.es/>
