PR tree-optimization/90879 - fold zero-equality of strcmp between a longer string and a smaller array

gcc/c-family/ChangeLog:

	PR tree-optimization/90879
	* c.opt (-Wstring-compare): New option.

gcc/testsuite/ChangeLog:

	PR tree-optimization/90879
	* gcc.dg/Wstring-compare-2.c: New test.
	* gcc.dg/Wstring-compare.c: New test.
	* gcc.dg/strcmpopt_3.c: Scan the optmized dump instead of strlen.
	* gcc.dg/strcmpopt_6.c: New test.
	* gcc.dg/strlenopt-65.c: Remove uinnecessary declarations, add
	test cases.
	* gcc.dg/strlenopt-66.c: Run it.
	* gcc.dg/strlenopt-68.c: New test.

gcc/ChangeLog:

	PR tree-optimization/90879
	* builtins.c (check_access): Avoid using maxbound when null.
	* calls.c (maybe_warn_nonstring_arg): Adjust to get_range_strlen change.
	* doc/invoke.texi (-Wstring-compare): Document new warning option.
	* gimple-fold.c (get_range_strlen_tree): Make setting maxbound
	conditional.
	(get_range_strlen): Overwrite initial maxbound when non-null.
	* gimple-ssa-sprintf.c (get_string_length): Adjust to get_range_strlen
	changes.
	* tree-ssa-strlen.c (maybe_diag_stxncpy_trunc): Same.
	(used_only_for_zero_equality): New function.
	(handle_builtin_memcmp): Call it.
	(determine_min_objsize): Return an integer instead of tree.
	(get_len_or_size, strxcmp_eqz_result): New functions.
	(maybe_warn_pointless_strcmp): New function.
	(handle_builtin_string_cmp): Call it.  Fold zero-equality of strcmp
	between a longer string and a smaller array.
	(get_range_strlen_dynamic): Overwrite initial maxbound when non-null.

From-SVN: r276773

1 files changed, 181 insertions, 0 deletions

diff --git a/gcc/testsuite/gcc.dg/Wstring-compare.c b/gcc/testsuite/gcc.dg/Wstring-compare.c
new file mode 100644
index 0000000..0ca492d
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/Wstring-compare.c
@@ -0,0 +1,181 @@
+/* PR tree-optimization/90879 - fold zero-equality of strcmp between
+   a longer string and a smaller array
+   { dg-do compile }
+   { dg-options "-O2 -Wall -Wextra -ftrack-macro-expansion=0" } */
+
+#include "strlenopt.h"
+
+#define T(a, b) sink (0 == strcmp (a, b), a, b)
+
+void sink (int, ...);
+
+struct S { char a4[4], c; };
+
+extern char a4[4];
+extern char a5[5];
+extern char b4[4];
+
+/* Verify that comparison of string literals with arrays with unknown
+   content but size that prevents them from comparing equal is diagnosed.  */
+
+void strcmp_array_lit (void)
+{
+  if (strcmp (a4, "1234"))  // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+                            // { dg-bogus "in this expreession" "unwanted note" { target *-*-* } .-1 }
+    sink (0, a4);
+
+  int cmp;
+  cmp = strcmp (a4, "1234");  // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+  if (cmp)                  // { dg-message "in this expression" }
+    sink (0, a4);
+
+  T (a4, "4321");           // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero " }
+  T (a4, "12345");          // { dg-warning "length 5 and an array of size 4 " }
+  T (a4, "123456");         // { dg-warning "length 6 and an array of size 4 " }
+  T ("1234", a4);           // { dg-warning "length 4 and an array of size 4 " }
+  T ("12345", a4);          // { dg-warning "length 5 and an array of size 4 " }
+  T ("123456", a4);         // { dg-warning "length 6 and an array of size 4 " }
+}
+
+
+void strcmp_array_pstr (void)
+{
+  const char *s4 = "1234";
+
+  {
+    if (strcmp (a4, s4))    // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+                            // { dg-bogus "in this expreession" "unwanted note" { target *-*-* } .-1 }
+      sink (1, a4);
+    else
+      sink (0, a4);
+  }
+
+  {
+    int c;
+    c = strcmp (a4, s4);    // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+    if (c)                  // { dg-message "in this expression" }
+      sink (1, a4);
+    else
+      sink (0, a4);
+  }
+
+  const char *t4 = "4321";
+  const char *s5 = "12345";
+  const char *s6 = "123456";
+
+  T (a4, t4);               // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero " }
+  T (a4, s5);               // { dg-warning "length 5 and an array of size 4 " }
+  T (a4, s6);               // { dg-warning "length 6 and an array of size 4 " }
+  T (s4, a4);               // { dg-warning "length 4 and an array of size 4 " }
+  T (s5, a4);               // { dg-warning "length 5 and an array of size 4 " }
+  T (s6, a4);               // { dg-warning "length 6 and an array of size 4 " }
+}
+
+
+void strcmp_array_cond_pstr (int i)
+{
+  const char *s4 = i ? "1234" : "4321";
+  T (a4, s4);               // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero " }
+  T (a5, s4);
+}
+
+void strcmp_array_copy (void)
+{
+  char s[8];
+
+  {
+    strcpy (s, "1234");
+    if (strcmp (a4, s))     // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+                            // { dg-bogus "in this expreession" "unwanted note" { target *-*-* } .-1 }
+      sink (1, a4);
+    else
+      sink (0, a4);
+  }
+
+  {
+    strcpy (s, "1234");
+
+    int c;
+    c = strcmp (a4, s);     // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero" }
+    if (c)                  // { dg-message "in this expression" }
+      sink (1, a4);
+    else
+      sink (0, a4);
+  }
+
+  strcpy (s, "4321");
+  T (a4, s);                // { dg-warning "'strcmp' of a string of length 4 and an array of size 4 evaluates to nonzero " }
+  strcpy (s, "12345");
+  T (a4, s);                // { dg-warning "length 5 and an array of size 4 " }
+  strcpy (s, "123456");
+  T (a4, s);                // { dg-warning "length 6 and an array of size 4 " }
+  strcpy (s, "4321");
+  T (s, a4);                // { dg-warning "length 4 and an array of size 4 " }
+  strcpy (s, "54321");
+  T (s, a4);                // { dg-warning "length 5 and an array of size 4 " }
+  strcpy (s, "654321");
+  T (s, a4);                // { dg-warning "length 6 and an array of size 4 " }
+}
+
+
+void strcmp_member_array_lit (const struct S *p)
+{
+  T (p->a4, "1234");        // { dg-warning "length 4 and an array of size 4 " }
+}
+
+
+#undef T
+#define T(a, b, n) sink (0 == strncmp (a, b, n), a, b)
+
+void strncmp_array_lit (void)
+{
+  if (strncmp (a4, "12345", 5))   // { dg-warning "'strncmp' of a string of length 5, an array of size 4 and bound of 5 evaluates to nonzero" }
+                                  // { dg-bogus "in this expreession" "unwanted note" { target *-*-* } .-1 }
+    sink (0, a4);
+
+  int cmp;
+  cmp = strncmp (a4, "54321", 5);   // { dg-warning "'strncmp' of a string of length 5, an array of size 4 and bound of 5 evaluates to nonzero" }
+  if (cmp)                          // { dg-message "in this expression" }
+    sink (0, a4);
+
+  // Verify no warning when the bound is the same as the array size.
+  T (a4, "4321", 4);
+  T (a4, "654321", 4);
+
+  T (a4, "12345", 5);       // { dg-warning "length 5, an array of size 4 and bound of 5 " }
+  T (a4, "123456", 6);      // { dg-warning "length 6, an array of size 4 and bound of 6" }
+
+  T ("1234", a4, 4);
+  T ("12345", a4, 4);
+
+  T ("12345", a4, 5);       // { dg-warning "length 5, an array of size 4 and bound of 5 " }
+  T ("123456", a4, 6);      // { dg-warning "length 6, an array of size 4 and bound of 6 " }
+}
+
+
+void strncmp_strarray_copy (void)
+{
+  {
+    char a[] = "1234";
+    char b[6];
+    strcpy (b, "12345");
+    if (strncmp (a, b, 5))  // { dg-warning "'strncmp' of strings of length 4 and 5 and bound of 5 evaluates to nonzero" }
+                            // { dg-bogus "in this expreession" "unwanted note" { target *-*-* } .-1 }
+      sink (0, a, b);
+  }
+
+  {
+    char a[] = "4321";
+    char b[6];
+    strcpy (b, "54321");
+    int cmp;
+    cmp = strncmp (a, b, 5);  // { dg-warning "'strncmp' of strings of length 4 and 5 and bound of 5 evaluates to nonzero" }
+    if (cmp)                  // { dg-message "in this expression" }
+      sink (0, a, b);
+  }
+
+  strcpy (a4, "abc");
+  T (a4, "54321", 5);       // { dg-warning "'strncmp' of strings of length 3 and 5 and bound of 5 evaluates to nonzero " }
+}
+
+