--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/Wstring-compare-2.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,127 @@
+/* PR tree-optimization/90879 - fold zero-equality of strcmp between
+   a longer string and a smaller array
+   Test for a warning for strcmp of a longer string against smaller
+   array.
+   { dg-do compile }
+   { dg-options "-O2 -Wall -Wstring-compare -Wno-stringop-truncation -ftrack-macro-expansion=0" } */
+
+typedef __SIZE_TYPE__ size_t;
+
+extern void* memcpy (void*, const void*, size_t);
+
+extern int strcmp (const char*, const char*);
+extern size_t strlen (const char*);
+extern char* strcpy (char*, const char*);
+extern char* strncpy (char*, const char*, size_t);
+extern int strncmp (const char*, const char*, size_t);
+
+void sink (int, ...);
+#define sink(...) sink (__LINE__, __VA_ARGS__)
+
+
+extern char a1[1], a2[2], a3[3], a4[4], a5[5], a6[6], a7[7], a8[8], a9[9];
+
+#define T(a, b) sink (0 == strcmp (a, b))
+
+
+void test_string_cst (void)
+{
+  const char *s1 = "1", *s2 = "12";
+
+  T (s1, a1);                 // { dg-warning ".strcmp. of a string of length 1 and an array of size 1 evaluates to nonzero" }
+  T (s1, a2);
+  T (s1, a3);
+
+  T (a1, s1);                 // { dg-warning ".strcmp. of a string of length 1 and an array of size 1 evaluates to nonzero" }
+  T (a2, s1);
+  T (a3, s1);
+
+  T (s2, a1);                 // { dg-warning ".strcmp. of a string of length 2 and an array of size 1 evaluates to nonzero" }
+  T (s2, a2);                 // { dg-warning ".strcmp. of a string of length 2 and an array of size 2 evaluates to nonzero" }
+  T (s2, a3);
+
+  T (a1, s2);                 // { dg-warning ".strcmp. of a string of length 2 and an array of size 1 evaluates to nonzero" }
+  T (a2, s2);                 // { dg-warning ".strcmp. of a string of length 2 and an array of size 2 evaluates to nonzero" }
+  T (a3, s2);
+}
+
+
+void test_string_cst_off_cst (void)
+{
+  const char *s1 = "1", *s2 = "12", *s3 = "123", *s4 = "1234";
+
+  T (s1, a2 + 1);              // { dg-warning ".strcmp. of a string of length 1 and an array of size 1 evaluates to nonzero" }
+  T (a2 + 1, s1);              // { dg-warning ".strcmp. of a string of length 1 and an array of size 1 evaluates to nonzero" }
+
+
+  T (s3 + 1, a2);             // { dg-warning ".strcmp. of a string of length 2 and an array of size 2 evaluates to nonzero" }
+  T (s3 + 1, a3);
+
+  T (s2, a4 + 1);
+  T (s2, a4 + 2);             // { dg-warning ".strcmp. of a string of length 2 and an array of size 2 evaluates to nonzero" }
+
+  T (s4, a4 + 1);             // { dg-warning ".strcmp. of a string of length 4 and an array of size 3 evaluates to nonzero" }
+  T (s3, a5 + 1);
+}
+
+
+/* Use strncpy below rather than memcpy until PR 91183 is resolved.  */
+
+#undef T
+#define T(s, n, a)					\
+  do {							\
+    char arr[32];					\
+    sink (arr);						\
+    strncpy (arr, s, n < 0 ? strlen (s) + 1: n);	\
+    sink (0 == strcmp (arr, a));			\
+  } while (0)
+
+void test_string_exact_length (void)
+{
+  const char *s1 = "1", *s2 = "12";
+
+  T (s1, -1, a1);             // { dg-warning ".strcmp. of a string of length 1 and an array of size 1 evaluates to nonzero" }
+  T (s1, -1, a2);
+  T (s1, -1, a3);
+
+  T (s2, -1, a1);             // { dg-warning ".strcmp. of a string of length 2 and an array of size 1 evaluates to nonzero" }
+  T (s2, -1, a2);             // { dg-warning ".strcmp. of a string of length 2 and an array of size 2 evaluates to nonzero" }
+  T (s2, -1, a3);
+}
+
+
+void test_string_min_length (void)
+{
+  const char *s1 = "1", *s2 = "12";
+
+  T (s1,  1, a1);             // { dg-warning ".strcmp. of a string of length 1 or more and an array of size 1 evaluates to nonzero" }
+  T (s1,  1, a2);
+  T (s1,  1, a3);
+
+  T (s2,  2, a1);             // { dg-warning ".strcmp. of a string of length 2 or more and an array of size 1 evaluates to nonzero" }
+  T (s2,  2, a2);             // { dg-warning ".strcmp. of a string of length 2 or more and an array of size 2 evaluates to nonzero" }
+  T (s2,  2, a3);
+}
+
+
+int test_strncmp_str_lit_var (const char *s, long n)
+{
+  if (strncmp (s, "123456", n) == 0)    // { dg-bogus "\\\[-Wstring-compare" }
+    return 1;
+
+  return 0;
+}
+
+int test_strlen_strncmp_str_lit_var (const char *s, long n)
+{
+  if (__builtin_strlen (s) < n)
+    return -1;
+
+  if (n == 6)
+    if (strncmp (s, "123456", n) == 0)  // { dg-bogus "\\\[-Wstring-compare" }
+      return 1;
+
+  return 0;
+}
+
+