On Tue, Jul 13, 2021 at 5:15 AM Alexandre Oliva <ol...@adacore.com> wrote:
>
>
> Odd-numbered indices describing argument access sizes in the fnspec
> string can only hold 't' or a digit, as tested in the beginning of the
> case. When checking that the size-supplying argument does not have
> additional information associated with it, the test that excludes the
> 't' possibility looks for it at the even position in the fnspec
> string. Oops.
>
> This might yield false positives and negatives if a function has a
> fnspec in which an argument uses a 't' access-size, and ('t' - '1')
> happens to be the index of an argument described in an fnspec string.
> Assuming ASCII encoding, it would take a function with at least 68
> arguments described in fnspec. Still, probably worth fixing.
>
> Regstrapped on x86_64-linux-gnu. I'm checking this in as obvious unless
> there are objections within some 48 hours.
oops - also worth backporting to affected branches.
Richard.
>
> for gcc/ChangeLog
>
> * tree-ssa-alias.c (attr_fnspec::verify): Fix index in
> non-'t'-sized arg check.
> ---
> gcc/tree-ssa-alias.c | 2 +-
> 1 file changed, 1 insertion(+), 1 deletion(-)
>
> diff --git a/gcc/tree-ssa-alias.c b/gcc/tree-ssa-alias.c
> index 0421bfac99869..742a95a549e20 100644
> --- a/gcc/tree-ssa-alias.c
> +++ b/gcc/tree-ssa-alias.c
> @@ -3895,7 +3895,7 @@ attr_fnspec::verify ()
> && str[idx] != 'w' && str[idx] != 'W'
> && str[idx] != 'o' && str[idx] != 'O')
> err = true;
> - if (str[idx] != 't'
> + if (str[idx + 1] != 't'
> /* Size specified is scalar, so it should be described
> by ". " if specified at all. */
> && (arg_specified_p (str[idx + 1] - '1')
>
>
> --
> Alexandre Oliva, happy hacker https://FSFLA.org/blogs/lxo/
> Free Software Activist GNU Toolchain Engineer
> Disinformation flourishes because many people care deeply about injustice
> but very few check the facts. Ask me about <https://stallmansupport.org>
