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