Hi!
The following patch fixes ICU miscompilation, where an initial part of a
buffer is initializer from non-zero terminated string literal (in ICU
actually from an array of non-zero chars that the FE newly turns into
non-zero terminated string literal), but the code recently added to
tree-ssa-strlen.c doesn't consider the possibility of string literals that
aren't zero terminated.
STRING_CSTs actually are always zero terminated, but if TREE_STRING_LENGTH
doesn't include the terminating character, it is just bytes.
Fixed thusly, bootstrapped/regtested on x86_64-linux and i686-linux, ok for
trunk?
I was considering using strnlen, but if all STRING_CSTs are actually zero
terminated, it will mean it reads are most one further byte and on many
targets strlen is more optimized than strnlen.
2019-01-04 Jakub Jelinek <ja...@redhat.com>
PR tree-optimization/88693
* tree-ssa-strlen.c (get_min_string_length): Don't set *full_string_p
for STRING_CSTs that don't contain any NUL characters in the first
TREE_STRING_LENGTH bytes.
* gcc.c-torture/execute/pr88693.c: New test.
--- gcc/tree-ssa-strlen.c.jj 2019-01-03 09:47:28.018069413 +0100
+++ gcc/tree-ssa-strlen.c 2019-01-04 16:28:47.549196405 +0100
@@ -3232,8 +3232,9 @@ get_min_string_length (tree rhs, bool *f
if (rhs && TREE_CODE (rhs) == STRING_CST)
{
- *full_string_p = true;
- return strlen (TREE_STRING_POINTER (rhs));
+ HOST_WIDE_INT len = strlen (TREE_STRING_POINTER (rhs));
+ *full_string_p = len < TREE_STRING_LENGTH (rhs);
+ return len;
}
return -1;
--- gcc/testsuite/gcc.c-torture/execute/pr88693.c.jj 2019-01-04
16:31:50.892218304 +0100
+++ gcc/testsuite/gcc.c-torture/execute/pr88693.c 2019-01-04
16:31:09.808885630 +0100
@@ -0,0 +1,54 @@
+/* PR tree-optimization/88693 */
+
+__attribute__((noipa)) void
+foo (char *p)
+{
+ if (__builtin_strlen (p) != 9)
+ __builtin_abort ();
+}
+
+__attribute__((noipa)) void
+quux (char *p)
+{
+ int i;
+ for (i = 0; i < 100; i++)
+ if (p[i] != 'x')
+ __builtin_abort ();
+}
+
+__attribute__((noipa)) void
+qux (void)
+{
+ char b[100];
+ __builtin_memset (b, 'x', sizeof (b));
+ quux (b);
+}
+
+__attribute__((noipa)) void
+bar (void)
+{
+ static unsigned char u[9] = "abcdefghi";
+ char b[100];
+ __builtin_memcpy (b, u, sizeof (u));
+ b[sizeof (u)] = 0;
+ foo (b);
+}
+
+__attribute__((noipa)) void
+baz (void)
+{
+ static unsigned char u[] = { 'j', 'k', 'l', 'm', 'n', 'o', 'p', 'q', 'r' };
+ char b[100];
+ __builtin_memcpy (b, u, sizeof (u));
+ b[sizeof (u)] = 0;
+ foo (b);
+}
+
+int
+main ()
+{
+ qux ();
+ bar ();
+ baz ();
+ return 0;
+}
Jakub
