[PATCH 1/2] c-family: -Waddress-of-packed-member and casts

[Jason Merrill <jason@redhat.com>]

Tested x86_64-pc-linux-gnu, OK for trunk?

-- 8< --

-Waddress-of-packed-member, in addition to the documented warning about
taking the address of a packed member, also warns about casting from
a pointer to a TYPE_PACKED type to a pointer to a type with greater
alignment.

This wrongly warns if the source is a pointer to enum when -fshort-enums
is on, since that is also represented by TYPE_PACKED.

And there's already -Wcast-align to catch casting from pointer to less
aligned type (packed or otherwise) to pointer to more aligned type; even
apart from the enum problem, this seems like a somewhat arbitrary subset of
that warning.  Though that isn't currently on by default.

So, this patch removes the undocumented type-based warning from
-Waddress-of-packed-member.  Some of the tests where the warning is
desirable I changed to use -Wcast-align=strict instead.  The ones that
require -Wno-incompatible-pointer-types, I just removed.

gcc/c-family/ChangeLog:

	* c-warn.cc (check_address_or_pointer_of_packed_member):
	Remove warning based on TYPE_PACKED.

gcc/testsuite/ChangeLog:

	* c-c++-common/Waddress-of-packed-member-1.c: Don't expect
	a warning on the cast cases.
	* c-c++-common/pr51628-35.c: Use -Wcast-align=strict.
	* g++.dg/warn/Waddress-of-packed-member3.C: Likewise.
	* gcc.dg/pr88928.c: Likewise.
	* gcc.dg/pr51628-20.c: Removed.
	* gcc.dg/pr51628-21.c: Removed.
	* gcc.dg/pr51628-25.c: Removed.
---
 gcc/c-family/c-warn.cc                        | 58 +------------------
 .../Waddress-of-packed-member-1.c             | 12 ++--
 gcc/testsuite/c-c++-common/pr51628-35.c       |  6 +-
 .../g++.dg/warn/Waddress-of-packed-member3.C  |  8 +--
 gcc/testsuite/gcc.dg/pr51628-20.c             | 11 ----
 gcc/testsuite/gcc.dg/pr51628-21.c             | 11 ----
 gcc/testsuite/gcc.dg/pr51628-25.c             |  9 ---
 gcc/testsuite/gcc.dg/pr88928.c                |  6 +-
 8 files changed, 19 insertions(+), 102 deletions(-)
 delete mode 100644 gcc/testsuite/gcc.dg/pr51628-20.c
 delete mode 100644 gcc/testsuite/gcc.dg/pr51628-21.c
 delete mode 100644 gcc/testsuite/gcc.dg/pr51628-25.c

diff --git a/gcc/c-family/c-warn.cc b/gcc/c-family/c-warn.cc
index d2938b91043..2a399ba6d14 100644
--- a/gcc/c-family/c-warn.cc
+++ b/gcc/c-family/c-warn.cc
@@ -2991,10 +2991,9 @@ check_alignment_of_packed_member (tree type, tree field, bool rvalue)
   return NULL_TREE;
 }
 
-/* Return struct or union type if the right hand value, RHS:
-   1. Is a pointer value which isn't aligned to a pointer type TYPE.
-   2. Is an address which takes the unaligned address of packed member
-      of struct or union when assigning to TYPE.
+/* Return struct or union type if the right hand value, RHS
+   is an address which takes the unaligned address of packed member
+   of struct or union when assigning to TYPE.
    Otherwise, return NULL_TREE.  */
 
 static tree
@@ -3021,57 +3020,6 @@ check_address_or_pointer_of_packed_member (tree type, tree rhs)
 
   type = TREE_TYPE (type);
 
-  if (TREE_CODE (rhs) == PARM_DECL
-      || VAR_P (rhs)
-      || TREE_CODE (rhs) == CALL_EXPR)
-    {
-      tree rhstype = TREE_TYPE (rhs);
-      if (TREE_CODE (rhs) == CALL_EXPR)
-	{
-	  rhs = CALL_EXPR_FN (rhs);	/* Pointer expression.  */
-	  if (rhs == NULL_TREE)
-	    return NULL_TREE;
-	  rhs = TREE_TYPE (rhs);	/* Pointer type.  */
-	  /* We could be called while processing a template and RHS could be
-	     a functor.  In that case it's a class, not a pointer.  */
-	  if (!rhs || !POINTER_TYPE_P (rhs))
-	    return NULL_TREE;
-	  rhs = TREE_TYPE (rhs);	/* Function type.  */
-	  rhstype = TREE_TYPE (rhs);
-	  if (!rhstype || !POINTER_TYPE_P (rhstype))
-	    return NULL_TREE;
-	  rvalue = true;
-	}
-      if (rvalue && POINTER_TYPE_P (rhstype))
-	rhstype = TREE_TYPE (rhstype);
-      while (TREE_CODE (rhstype) == ARRAY_TYPE)
-	rhstype = TREE_TYPE (rhstype);
-      if (TYPE_PACKED (rhstype))
-	{
-	  unsigned int type_align = min_align_of_type (type);
-	  unsigned int rhs_align = min_align_of_type (rhstype);
-	  if (rhs_align < type_align)
-	    {
-	      auto_diagnostic_group d;
-	      location_t location = EXPR_LOC_OR_LOC (rhs, input_location);
-	      if (warning_at (location, OPT_Waddress_of_packed_member,
-			      "converting a packed %qT pointer (alignment %d) "
-			      "to a %qT pointer (alignment %d) may result in "
-			      "an unaligned pointer value",
-			      rhstype, rhs_align, type, type_align))
-		{
-		  tree decl = TYPE_STUB_DECL (rhstype);
-		  if (decl)
-		    inform (DECL_SOURCE_LOCATION (decl), "defined here");
-		  decl = TYPE_STUB_DECL (type);
-		  if (decl)
-		    inform (DECL_SOURCE_LOCATION (decl), "defined here");
-		}
-	    }
-	}
-      return NULL_TREE;
-    }
-
   tree context = NULL_TREE;
 
   /* Check alignment of the object.  */
diff --git a/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c b/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
index 95a376664da..0f5188df70a 100644
--- a/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
+++ b/gcc/testsuite/c-c++-common/Waddress-of-packed-member-1.c
@@ -52,12 +52,12 @@ void foo (void)
   f0 = *&__real__ t0.f;        /* { dg-bogus "may result in an unaligned pointer value" } */
   f0 = *&__imag__ t0.f;        /* { dg-bogus "may result in an unaligned pointer value" } */
   i1 = (&t0.c, (int*) 0);      /* { dg-bogus "may result in an unaligned pointer value" } */
-  t2 = (struct t**) t10;     /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
-  t2 = (struct t**) t100;    /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
-  t2 = (struct t**) t1;      /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
-  t2 = (struct t**) bar();   /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
-  t2 = (struct t**) baz();   /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
-  t2 = (struct t**) bazz();  /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
+  t2 = (struct t**) t10;       /* { dg-bogus "may result in an unaligned pointer value" } */
+  t2 = (struct t**) t100;      /* { dg-bogus "may result in an unaligned pointer value" } */
+  t2 = (struct t**) t1;        /* { dg-bogus "may result in an unaligned pointer value" } */
+  t2 = (struct t**) bar();     /* { dg-bogus "may result in an unaligned pointer value" } */
+  t2 = (struct t**) baz();     /* { dg-bogus "may result in an unaligned pointer value" } */
+  t2 = (struct t**) bazz();    /* { dg-bogus "may result in an unaligned pointer value" } */
   i1 = &t0.b;                /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
   i1 = &t1->b;               /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
   i1 = &t10[0].b;            /* { dg-warning "may result in an unaligned pointer value" ""  { target { ! default_packed } } } */
diff --git a/gcc/testsuite/c-c++-common/pr51628-35.c b/gcc/testsuite/c-c++-common/pr51628-35.c
index fa37d99beb7..a88c19ea0df 100644
--- a/gcc/testsuite/c-c++-common/pr51628-35.c
+++ b/gcc/testsuite/c-c++-common/pr51628-35.c
@@ -1,6 +1,6 @@
 /* PR c/51628.  */
 /* { dg-do compile } */
-/* { dg-options "-O" } */
+/* { dg-options "-O -Wcast-align=strict" } */
 
 struct B { int i; };
 struct C { struct B b; } __attribute__ ((packed));
@@ -12,12 +12,12 @@ long *
 foo1 (void)
 {
   return (long *) p;
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
+/* { dg-warning "increases required alignment" "" { target { ! default_packed } } .-1 } */
 }
 
 long *
 foo2 (void)
 {
   return (long *) bar ();
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
+/* { dg-warning "increases required alignment" "" { target { ! default_packed } } .-1 } */
 }
diff --git a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
index aeffb969c01..28dd05d366c 100644
--- a/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
+++ b/gcc/testsuite/g++.dg/warn/Waddress-of-packed-member3.C
@@ -1,5 +1,5 @@
 // { dg-do compile { target { ! default_packed } } }
-// Test that -Waddress-of-packed-member works with member functions.
+// { dg-additional-options -Wcast-align=strict }
 
 struct S {
   char c;
@@ -16,8 +16,8 @@ S**
 f ()
 {
   S **s;
-  s = reinterpret_cast<S**>(foo ()); // { dg-warning "converting a packed" }
-  s = reinterpret_cast<S**>(x.memfn ()); // { dg-warning "converting a packed" }
-  s = reinterpret_cast<S**>(X::smemfn ()); // { dg-warning "converting a packed" }
+  s = reinterpret_cast<S**>(foo ()); // { dg-warning "increases required alignment" }
+  s = reinterpret_cast<S**>(x.memfn ()); // { dg-warning "increases required alignment" }
+  s = reinterpret_cast<S**>(X::smemfn ()); // { dg-warning "increases required alignment" }
   return s;
 }
diff --git a/gcc/testsuite/gcc.dg/pr51628-20.c b/gcc/testsuite/gcc.dg/pr51628-20.c
deleted file mode 100644
index 2249d85098b..00000000000
--- a/gcc/testsuite/gcc.dg/pr51628-20.c
+++ /dev/null
@@ -1,11 +0,0 @@
-/* PR c/51628.  */
-/* { dg-do compile } */
-/* { dg-options "-O -Wno-incompatible-pointer-types" } */
-
-struct B { int i; };
-struct C { struct B b; } __attribute__ ((packed));
-
-extern struct C *p;
-
-long* g8 (void) { return p; }
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
diff --git a/gcc/testsuite/gcc.dg/pr51628-21.c b/gcc/testsuite/gcc.dg/pr51628-21.c
deleted file mode 100644
index f1adbe64002..00000000000
--- a/gcc/testsuite/gcc.dg/pr51628-21.c
+++ /dev/null
@@ -1,11 +0,0 @@
-/* PR c/51628.  */
-/* { dg-do compile } */
-/* { dg-options "-O -Wno-incompatible-pointer-types" } */
-
-struct B { int i; };
-struct C { struct B b; } __attribute__ ((packed));
-
-extern struct C p[];
-
-long* g8 (void) { return p; }
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
diff --git a/gcc/testsuite/gcc.dg/pr51628-25.c b/gcc/testsuite/gcc.dg/pr51628-25.c
deleted file mode 100644
index f00d9b1bcac..00000000000
--- a/gcc/testsuite/gcc.dg/pr51628-25.c
+++ /dev/null
@@ -1,9 +0,0 @@
-/* PR c/51628.  */
-/* { dg-do compile } */
-/* { dg-options "-O -Wno-incompatible-pointer-types" } */
-
-struct B { int i; };
-struct C { struct B b; } __attribute__ ((packed));
-
-long* g8 (struct C *p) { return p; }
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
diff --git a/gcc/testsuite/gcc.dg/pr88928.c b/gcc/testsuite/gcc.dg/pr88928.c
index 0b6c1d70f05..1d176d6d51d 100644
--- a/gcc/testsuite/gcc.dg/pr88928.c
+++ b/gcc/testsuite/gcc.dg/pr88928.c
@@ -1,6 +1,6 @@
-/* { dg-do compile } */
-/* { dg-options "-Wno-pedantic -Waddress-of-packed-member" } */
+/* { dg-do compile { target { ! default_packed } } } */
+/* { dg-options "-Wno-pedantic -Waddress-of-packed-member -Wcast-align=strict" } */
 struct a { } __attribute__((__packed__));
 void c (struct a **);
 void d (const struct a *b) { c ((struct a **) b); }
-/* { dg-warning "may result in an unaligned pointer value" "" { target { ! default_packed } } .-1 } */
+/* { dg-warning "increases required alignment" "" { target *-*-* } .-1 } */

base-commit: 65bd6de0de57abc86931a5e0b9a8d453ad530004
-- 
2.39.3