From 37b64a3547b91677189c6cbf4c08d7c80770a93a Mon Sep 17 00:00:00 2001 From: Jakub Jelinek Date: Tue, 23 Feb 2021 09:49:48 +0100 Subject: fold-const: Fix ICE in fold_read_from_constant_string on invalid code [PR99204] fold_read_from_constant_string and expand_expr_real_1 have code to optimize constant reads from string (tree vs. rtl). If the STRING_CST array type has zero low bound, index is fold converted to sizetype and so the compare_tree_int works fine, but if it has some other low bound, it calls size_diffop_loc and that function from 2 sizetype operands creates a ssizetype difference. expand_expr_real_1 then uses tree_fits_uhwi_p + compare_tree_int and so works fine, but fold-const.c only checked if index is INTEGER_CST and calls compare_tree_int, which means for negative index it will succeed and result in UB in the compiler. 2021-02-23 Jakub Jelinek PR tree-optimization/99204 * fold-const.c (fold_read_from_constant_string): Check that tree_fits_uhwi_p (index) rather than just that index is INTEGER_CST. * gfortran.dg/pr99204.f90: New test. --- gcc/fold-const.c | 2 +- gcc/testsuite/gfortran.dg/pr99204.f90 | 10 ++++++++++ 2 files changed, 11 insertions(+), 1 deletion(-) create mode 100644 gcc/testsuite/gfortran.dg/pr99204.f90 diff --git a/gcc/fold-const.c b/gcc/fold-const.c index c35f987ab89..afc3b7f8772 100644 --- a/gcc/fold-const.c +++ b/gcc/fold-const.c @@ -15433,7 +15433,7 @@ fold_read_from_constant_string (tree exp) if (string && TYPE_MODE (TREE_TYPE (exp)) == TYPE_MODE (TREE_TYPE (TREE_TYPE (string))) && TREE_CODE (string) == STRING_CST - && TREE_CODE (index) == INTEGER_CST + && tree_fits_uhwi_p (index) && compare_tree_int (index, TREE_STRING_LENGTH (string)) < 0 && is_int_mode (TYPE_MODE (TREE_TYPE (TREE_TYPE (string))), &char_mode) diff --git a/gcc/testsuite/gfortran.dg/pr99204.f90 b/gcc/testsuite/gfortran.dg/pr99204.f90 new file mode 100644 index 00000000000..9b6f27fa3d2 --- /dev/null +++ b/gcc/testsuite/gfortran.dg/pr99204.f90 @@ -0,0 +1,10 @@ +! PR tree-optimization/99204 +! { dg-do compile } +! { dg-options "-O2 -w" } + +program pr99204 + character :: c + integer :: i = -12345678 + c = 'abc'(i:i) + print *, c +end -- cgit v1.2.1