From: Alfie Richards <alfie.richards@arm.com>
Date: Mon, 28 Jul 2025 13:32:45 +0000 (+0000)
Subject: Fix UB in string_slice::operator== (PR 121261)
X-Git-Url: http://git.ipfire.org/?a=commitdiff_plain;h=c1102be3b25bde9989561b2610f8ee721a33a8e7;p=thirdparty%2Fgcc.git

Fix UB in string_slice::operator== (PR 121261)

This adds a nullptr check to fix a regression where it is possible to call
`memcmp (NULL, NULL, 0)` which is UB prior to C26.

This fixes the bootstrap-ubsan build.

gcc/ChangeLog:
	PR middle-end/121261
	* vec.h: Add null ptr check.
---

diff --git a/gcc/vec.h b/gcc/vec.h
index 9604edb1c3c..0ea7a495734 100644
--- a/gcc/vec.h
+++ b/gcc/vec.h
@@ -2514,6 +2514,10 @@ public:
       return false;
     if (lhs.size () != rhs.size ())
       return false;
+    /* Case where either is a NULL pointer and therefore, as both are valid,
+       both are empty slices with length 0.  */
+    if (lhs.size () == 0)
+      return true;
     return memcmp (lhs.begin (), rhs.begin (), lhs.size ()) == 0;
   }