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From: "jason at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
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Subject: [Bug middle-end/103483] context-sensitive ranges change triggers
 stringop-overread
Date: Sat, 11 Dec 2021 22:43:52 +0000
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https://gcc.gnu.org/bugzilla/show_bug.cgi?id=3D103483

--- Comment #14 from Jason Merrill <jason at gcc dot gnu.org> ---
(In reply to Martin Sebor from comment #13)
> static inline void copy (const char *p)
> {
>   int N =3D null_safe_strlen (p);
>   if (N) /* disabling this branch prevents the warning */
>     __builtin_memcpy (sink, p, N);
>   else
>     *sink =3D 0;
> }

This testcase is importantly different from mine; in mine the branch itself=
 is
what introduces the range information that causes the warning, we only deci=
de
that the statement is invalid because of the if.  In your testcase, if you =
made
the memcpy unconditional we would still warn; in mine we only warn *because*
it's conditional.=