c++: Completeness of typedef structs [PR 99294]

When we read in a class definition, we use fixup_type_variants to
propagate the now-completed fields of the class's TYPE to other
variants.  Unfortunately that doesn't propagate all of them, and in
this case we had a typedef to an (incomplete) instantiation.  That
typedef ended up with a VOIDmode, which blew up gimple expansion as
the type itself isn't VOID.  Without modules, that information is
propagated in finalize_type_size when laying out the class.  But that
doesn't happen with stream-in -- we already know the layout.  There is
already some overlap between the two functions, now there's a bit
more.  In fixup_type_variants, I pay attention to the TYPE_NAME to
decide whether to override a user's TYPE_ALIGN -- variants of the
main-variant typedef just copy the main-variant.  Other variants
recalculate.  Overaligning is still permitted.

I also added a TYPE_ALIGN_RAW accessor, and fixed a bug in the
alignment streaming I noticed.  I did not refactor TYPE_ALIGN beyond
using the new accessor.  (It could be written as ((1 << align_raw) >>
1), rather than use the conditional.)

	PR c++/99294
	gcc/
	* tree.h (TYPE_ALIGN_RAW): New accessor.
	(TYPE_ALIGN): Use it.
	gcc/cp/
	* class.c (fixup_type_variants): Propagate mode, precision,
	alignment & emptiness.
	* module.cc (trees_out::type_node): Use TYPE_ALIGN_RAW.
	(trees_in::tree_node): Rematerialize alignment here.
	gcc/testsuite/
	* g++.dg/modules/pr99294.h: New.
	* g++.dg/modules/pr99294_a.C: New.
	* g++.dg/modules/pr99294_b.C: New.

1 files changed, 28 insertions, 18 deletions

diff --git a/gcc/cp/class.c b/gcc/cp/class.c
index 40f5fef..ea007e8 100644
--- a/gcc/cp/class.c
+++ b/gcc/cp/class.c
@@ -2005,35 +2005,45 @@ determine_primary_bases (tree t)
 /* Update the variant types of T.  */
 
 void
-fixup_type_variants (tree t)
+fixup_type_variants (tree type)
 {
-  tree variants;
-
-  if (!t)
+  if (!type)
     return;
 
-  for (variants = TYPE_NEXT_VARIANT (t);
-       variants;
-       variants = TYPE_NEXT_VARIANT (variants))
+  for (tree variant = TYPE_NEXT_VARIANT (type);
+       variant;
+       variant = TYPE_NEXT_VARIANT (variant))
     {
       /* These fields are in the _TYPE part of the node, not in
 	 the TYPE_LANG_SPECIFIC component, so they are not shared.  */
-      TYPE_HAS_USER_CONSTRUCTOR (variants) = TYPE_HAS_USER_CONSTRUCTOR (t);
-      TYPE_NEEDS_CONSTRUCTING (variants) = TYPE_NEEDS_CONSTRUCTING (t);
-      TYPE_HAS_NONTRIVIAL_DESTRUCTOR (variants)
-	= TYPE_HAS_NONTRIVIAL_DESTRUCTOR (t);
+      TYPE_HAS_USER_CONSTRUCTOR (variant) = TYPE_HAS_USER_CONSTRUCTOR (type);
+      TYPE_NEEDS_CONSTRUCTING (variant) = TYPE_NEEDS_CONSTRUCTING (type);
+      TYPE_HAS_NONTRIVIAL_DESTRUCTOR (variant)
+	= TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type);
 
-      TYPE_POLYMORPHIC_P (variants) = TYPE_POLYMORPHIC_P (t);
-      CLASSTYPE_FINAL (variants) = CLASSTYPE_FINAL (t);
+      TYPE_POLYMORPHIC_P (variant) = TYPE_POLYMORPHIC_P (type);
+      CLASSTYPE_FINAL (variant) = CLASSTYPE_FINAL (type);
 
-      TYPE_BINFO (variants) = TYPE_BINFO (t);
+      TYPE_BINFO (variant) = TYPE_BINFO (type);
 
       /* Copy whatever these are holding today.  */
-      TYPE_VFIELD (variants) = TYPE_VFIELD (t);
-      TYPE_FIELDS (variants) = TYPE_FIELDS (t);
+      TYPE_VFIELD (variant) = TYPE_VFIELD (type);
+      TYPE_FIELDS (variant) = TYPE_FIELDS (type);
+
+      TYPE_SIZE (variant) = TYPE_SIZE (type);
+      TYPE_SIZE_UNIT (variant) = TYPE_SIZE_UNIT (type);
+
+      if (!TYPE_USER_ALIGN (variant)
+	  || TYPE_NAME (variant) == TYPE_NAME (type)
+	  || TYPE_ALIGN_RAW (variant) < TYPE_ALIGN_RAW (type))
+	{
+	  TYPE_ALIGN_RAW (variant) =  TYPE_ALIGN_RAW (type);
+	  TYPE_USER_ALIGN (variant) = TYPE_USER_ALIGN (type);
+	}
 
-      TYPE_SIZE (variants) = TYPE_SIZE (t);
-      TYPE_SIZE_UNIT (variants) = TYPE_SIZE_UNIT (t);
+      TYPE_PRECISION (variant) = TYPE_PRECISION (type);
+      TYPE_MODE_RAW (variant) = TYPE_MODE_RAW (type);
+      TYPE_EMPTY_P (variant) = TYPE_EMPTY_P (type);
     }
 }