Fix use of COMPLETE_TYPE_P for -Wstrict-aliasing=1

The handling of -Wstrict-aliasing=1 applied COMPLETE_TYPE_P to the
pointer type rather than the pointer target, so missed the warnings
for "struct incomplete" in the testcase.

I couldn't find any existing C tests for -Wstrict-aliasing=1,
so I added a few extra tests besides the ones fixed by the patch.
I'm sure there's lots more we could test -- this is just supposed
to be better than the status quo (i.e. nothing).

2019-04-26  Richard Sandiford  <richard.sandiford@arm.com>

gcc/c-family/
	* c-warn.c (strict_aliasing_warning): Apply COMPLETE_TYPE_P to
	the pointer target rather than the pointer itself.

gcc/testsuite/
	* gcc.dg/alias-16.c: New test.

From-SVN: r270594

4 files changed, 56 insertions, 1 deletions

diff --git a/gcc/c-family/ChangeLog b/gcc/c-family/ChangeLog
index 12d4587..9a662f0 100644
--- a/gcc/c-family/ChangeLog
+++ b/gcc/c-family/ChangeLog
@@ -1,3 +1,8 @@
+2019-04-26  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* c-warn.c (strict_aliasing_warning): Apply COMPLETE_TYPE_P to
+	the pointer target rather than the pointer itself.
+
 2019-04-19  Jakub Jelinek  <jakub@redhat.com>
 
 	PR c/89888
diff --git a/gcc/c-family/c-warn.c b/gcc/c-family/c-warn.c
index 322cf98..f95eba9 100644
--- a/gcc/c-family/c-warn.c
+++ b/gcc/c-family/c-warn.c
@@ -746,7 +746,7 @@ strict_aliasing_warning (location_t loc, tree type, tree expr)
 	 are not revealed at higher levels.  */
       alias_set_type set1 = get_alias_set (TREE_TYPE (otype));
       alias_set_type set2 = get_alias_set (TREE_TYPE (type));
-      if (!COMPLETE_TYPE_P (type)
+      if (!COMPLETE_TYPE_P (TREE_TYPE (type))
 	  || !alias_sets_must_conflict_p (set1, set2))
 	{
 	  warning_at (loc, OPT_Wstrict_aliasing,
diff --git a/gcc/testsuite/ChangeLog b/gcc/testsuite/ChangeLog
index 5ea04dc..90e8d8b 100644
--- a/gcc/testsuite/ChangeLog
+++ b/gcc/testsuite/ChangeLog
@@ -1,3 +1,7 @@
+2019-04-26  Richard Sandiford  <richard.sandiford@arm.com>
+
+	* gcc.dg/alias-16.c: New test.
+
 2019-04-25  Martin Liska  <mliska@suse.cz>
 	    H.J. Lu  <hongjiu.lu@intel.com>
 
diff --git a/gcc/testsuite/gcc.dg/alias-16.c b/gcc/testsuite/gcc.dg/alias-16.c
new file mode 100644
index 0000000..8f5aa35
--- /dev/null
+++ b/gcc/testsuite/gcc.dg/alias-16.c
@@ -0,0 +1,46 @@
+/* { dg-do compile } */
+/* { dg-options "-Wstrict-aliasing=1 -fstrict-aliasing" } */
+
+struct incomplete;
+struct s1 { int i; };
+struct s2 { double d; };
+
+void
+f (int *i, double *d, struct s1 *s1, struct s2 *s2, char *c)
+{
+  (char *) i;
+  (char *) d;
+  (char *) s1;
+  (char *) s2;
+  (char *) c;
+
+  (int *) i;
+  (int *) d; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (int *) s1; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (int *) s2; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (int *) c;
+
+  (double *) i; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (double *) d;
+  (double *) s1; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (double *) s2; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (double *) c;
+
+  (struct incomplete *) i; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct incomplete *) d; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct incomplete *) s1; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct incomplete *) s2; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct incomplete *) c; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+
+  (struct s1 *) i; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s1 *) d; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s1 *) s1;
+  (struct s1 *) s2; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s1 *) c;
+
+  (struct s2 *) i; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s2 *) d; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s2 *) s1; /* { dg-warning "dereferencing type-punned pointer might break strict-aliasing rules" } */
+  (struct s2 *) s2;
+  (struct s2 *) c;
+}