--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/gcc/testsuite/gcc.dg/Wbuiltin-declaration-mismatch-4.c	Thu Feb 13 11:34:05 2020 +0900
@@ -0,0 +1,153 @@
+/* PR c/83656 - missing -Wbuiltin-declaration-mismatch on declaration
+   without prototype
+   { dg-do compile }
+   { dg-options "-Wbuiltin-declaration-mismatch" } */
+
+typedef __PTRDIFF_TYPE__ ptrdiff_t;
+typedef __SIZE_TYPE__    size_t;
+
+char c;
+signed char sc;
+unsigned char uc;
+short si;
+unsigned short usi;
+int i;
+unsigned ui;
+long li;
+unsigned long uli;
+
+size_t szi;
+typedef size_t SizeType;
+SizeType szti;
+
+ptrdiff_t diffi;
+
+enum E { e0 } e;
+
+float f;
+double d;
+long double ld;
+
+
+/* Verify warnings for undefined calls to built-ins expecting integer
+   arguments.  */
+
+int abs ();         /* { dg-message "built-in .abs. declared here" } */
+
+void test_integer_conversion_abs (void)
+{
+  i = abs (c);
+  i = abs (sc);
+  i = abs (uc);
+
+  i = abs (si);
+  i = abs (usi);
+
+  i = abs (i);
+  i = abs (ui);     /* { dg-warning ".abs. argument 1 type is .unsigned int. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  i = __builtin_abs (ui);
+
+  i = abs (li);     /* { dg-warning ".abs. argument 1 type is .long int. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (uli);    /* { dg-warning ".abs. argument 1 type is .long unsigned int. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  i = abs (e0);
+  i = abs (e);
+
+  i = abs (-1.0);   /* { dg-warning ".abs. argument 1 type is .double. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (f);      /* { dg-warning ".abs. argument 1 promotes to .double. where .int. is expected in a call to built-in function declared without prototype" } */
+  i = abs (ld);     /* { dg-warning ".abs. argument 1 type is .long double. where .int. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  i = __builtin_abs (ld);
+}
+
+
+extern void* memset ();
+
+void test_integer_conversion_memset (void *d)
+{
+  memset (d, 0, sizeof (int));
+  memset (d, '\0', szi);
+  memset (d, i, szti);
+
+  /* Passing a ptrdiff_t where size_t is expected may not be unsafe
+     but because GCC may emits suboptimal code for such calls warning
+     for them helps improve efficiency.  */
+  memset (d, 0, diffi);       /* { dg-warning ".memset. argument 3 promotes to .ptrdiff_t. {aka .\(long \)?int.} where .\(long \)?unsigned int. is expected" } */
+
+  memset (d, 0, 2.0);         /* { dg-warning ".memset. argument 3 type is .double. where '\(long \)?unsigned int' is expected" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  __builtin_memset (d, 0.0, 4.0);
+}
+
+
+/* Verify warnings for undefined calls to built-ins expecting floating
+   arguments.  */
+
+double fabs ();           /* { dg-message "built-in .fabs. declared here" } */
+
+/* Expect a warning for fabsf below because even a float argument promotes
+   to double.  Unfortunately, invalid calls to fabsf() are not diagnosed.  */
+float fabsf ();           /* { dg-warning "conflicting types for built-in function .fabsf.; expected .float\\\(float\\\)." } */
+long double fabsl ();     /* { dg-message "built-in .fabsl. declared here" } */
+
+void test_real_conversion_fabs (void)
+{
+  d = fabs (c);     /* { dg-warning ".fabs. argument 1 promotes to .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (i);     /* { dg-warning ".fabs. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (li);    /* { dg-warning ".fabs. argument 1 type is .long int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  /* In C, the type of an enumeration constant is int.  */
+  d = fabs (e0);    /* { dg-warning ".fabs. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabs (e);     /* { dg-warning ".fabs. argument 1 type is .enum E. where .double. is expected in a call to built-in function declared without prototype" "ordinary enum" { target { ! short_enums } } } */
+  /* { dg-warning ".fabs. argument 1 promotes to .int. where .double. is expected in a call to built-in function declared without prototype" "size 1 enum" { target short_enums } .-1 } */
+
+  /* No warning here since float is promoted to double.  */
+  d = fabs (f);
+
+  d = fabs (ld);    /* { dg-warning ".fabs. argument 1 type is .long double. where .double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabsf (c);    /* { dg-warning ".fabsf. argument 1 promotes to .int. where .float. is expected in a call to built-in function declared without prototype" "pr87890" { xfail *-*-* } } */
+
+  d = fabsl (c);    /* { dg-warning ".fabsl. argument 1 promotes to .int. where .long double. is expected in a call to built-in function declared without prototype" } */
+
+  d = fabsl (f);    /* { dg-warning ".fabsl. argument 1 promotes to .double. where .long double. is expected in a call to built-in function declared without prototype" } */
+
+  /* Verify that the same call as above but to the built-in doesn't
+     trigger a warning.  */
+  d = __builtin_fabsl (f);
+}
+
+/* Verify warnings for calls to a two-argument real function.  */
+
+double pow ();      /* { dg-message "built-in .pow. declared here" } */
+
+void test_real_conversion_pow (void)
+{
+  d = pow (2.0, 2.0);
+  d = pow (d, 3.0);
+  d = pow (d, d);
+
+  d = pow (2, 3.0); /* { dg-warning ".pow. argument 1 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+  d = pow (3.0, 2); /* { dg-warning ".pow. argument 2 type is .int. where .double. is expected in a call to built-in function declared without prototype" } */
+}
+
+
+/* Verify warnings for calls that discard qualifiers.  */
+
+extern void* memcpy ();
+
+void test_qual_conversion_memcpy (void *d, const void *s)
+{
+  memcpy (d, s, sizeof (int));
+  memcpy (s, d, sizeof (int));    /* { dg-warning "passing argument 1 of .memcpy. discards 'const' qualifier from pointer target type" } */
+}