From 39737cdf002637c7a652e9c3e36f369cfce581e5 Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Tue, 12 Mar 2024 10:23:19 +0100 Subject: [PATCH] strlen: Fix another spot that can create invalid ranges [PR114293] This PR is similar to PR110603 fixed with r14-8487, except in a different spot. From the memset with -1 size of non-zero value we determine minimum of (size_t) -1 and the code uses PTRDIFF_MAX - 2 (not really sure I understand why it is - 2 and not - 1, e.g. heap allocated array with PTRDIFF_MAX char elements which contain '\0' in the last element should be fine, no? One can still represent arr[PTRDIFF_MAX] - arr[0] and arr[0] - arr[PTRDIFF_MAX] in ptrdiff_t and strlen (arr) == PTRDIFF_MAX - 1) as the maximum, so again invalid range. As in the other case, it is just UB that can lead to that, and we have choice to only keep the min and use +inf for max, or only keep max and use 0 for min, or not set the range at all, or use [min, min] or [max, max] etc. The following patch uses [min, +inf]. 2024-03-12 Jakub Jelinek PR tree-optimization/114293 * tree-ssa-strlen.cc (strlen_pass::handle_builtin_strlen): If max is smaller than min, set max to ~(size_t)0. * gcc.dg/pr114293.c: New test. --- gcc/testsuite/gcc.dg/pr114293.c | 10 ++++++++++ gcc/tree-ssa-strlen.cc | 2 ++ 2 files changed, 12 insertions(+) create mode 100644 gcc/testsuite/gcc.dg/pr114293.c diff --git a/gcc/testsuite/gcc.dg/pr114293.c b/gcc/testsuite/gcc.dg/pr114293.c new file mode 100644 index 000000000000..eb49ede0657d --- /dev/null +++ b/gcc/testsuite/gcc.dg/pr114293.c @@ -0,0 +1,10 @@ +/* PR tree-optimization/114293 */ +/* { dg-do compile } */ +/* { dg-options "-O2 -w" } */ + +int +foo (int x) +{ + __builtin_memset (&x, 5, -1); + return __builtin_strlen ((char *) &x); +} diff --git a/gcc/tree-ssa-strlen.cc b/gcc/tree-ssa-strlen.cc index 20540c529482..e09c9cc081f5 100644 --- a/gcc/tree-ssa-strlen.cc +++ b/gcc/tree-ssa-strlen.cc @@ -2341,6 +2341,8 @@ strlen_pass::handle_builtin_strlen () wide_int min = wi::to_wide (old); wide_int max = wi::to_wide (TYPE_MAX_VALUE (ptrdiff_type_node)) - 2; + if (wi::gtu_p (min, max)) + max = wi::to_wide (TYPE_MAX_VALUE (TREE_TYPE (lhs))); set_strlen_range (lhs, min, max); } else -- 2.43.5