[PATCH 01/11] Array: avoided void pointer arithmetic in nxt_array_copy().
alx.manpages at gmail.com
Thu Jun 16 15:41:02 UTC 2022
On 6/16/22 03:00, Andrew Clayton wrote:
> As was pointed out by the cppcheck static code analysis utility we
> were doing void pointer arithmetic on src->elts which is technically
> undefined behaviour.
> While GCC allows this by treating the size of void as 1. Same with
> Clang. Other compilers I'm not sure about, so lets just be safe and cast
> src->nelts to (char *) where sizeof(char) is guaranteed to be 1.
> : https://cppcheck.sourceforge.io/
> : https://gcc.gnu.org/onlinedocs/gcc/Pointer-Arith.html
That is one of the GNU extensions I wish was in the standard, at least
I hate casts for the danger they pose by shutting (almost) all warnings
off, and I think that danger is more real than the possible dangers
caused by pointer arithmetics on `void *`.
In fact, the worst thing that could happen would be that the compiler
refuses to compile, but if it compiles, it's almost forced to use `char
*` rules, due to:
6.2.5-27: A pointer to void shall have the same representation and
alignment requirements as a pointer to a character type.
Since we seem to have support from all compilers we care (otherwise one
would have already complained), I prefer not fixing this.
So, wontfix? :)
BTW, if you would like to CC me in patches to the mailing list, it would
help me notice them.
> src/nxt_array.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
> diff --git a/src/nxt_array.c b/src/nxt_array.c
> index 1e13c22..0a7945e 100644
> --- a/src/nxt_array.c
> +++ b/src/nxt_array.c
> @@ -140,7 +140,7 @@ nxt_array_copy(nxt_mp_t *mp, nxt_array_t *dst, nxt_array_t *src)
> return NULL;
> - nxt_memcpy(data, src->elts + (i * size), size);
> + nxt_memcpy(data, (char *) src->elts + (i * size), size);
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