diff mbox series

c++: alias template template_info setting

Message ID 0bf8ca9b-70d8-202b-e672-1e275d73aaab@acm.org
State New
Headers show
Series c++: alias template template_info setting | expand

Commit Message

Nathan Sidwell Aug. 18, 2020, 9:52 p.m. UTC 
During the construction of alias templates we can alter its
template_info.  This is really weird, because that's morally immutable
data.  In this case it's ok, but let's not create a duplicate
template_info, and add asserts to make sure it is changing in exactly
the way we expect.

Needless to say modules fell over the duplicated template_info and got 
very confused.

         gcc/cp/
         * cp-tree.h (SET_TYPE_TEMPLTE_INFO): Do not deal with ALIAS 
templates.
         * pt.c (lookup_template_class_1): Special-case alias template
         template_info setting.
diff mbox series

Patch

diff --git i/gcc/cp/cp-tree.h w/gcc/cp/cp-tree.h
index 04758574019..5f2c7e574c4 100644
--- i/gcc/cp/cp-tree.h
+++ w/gcc/cp/cp-tree.h
@@ -3485,13 +3485,12 @@  struct GTY(()) lang_decl {
    ? TYPE_ALIAS_TEMPLATE_INFO (NODE)					\
    : TYPE_TEMPLATE_INFO (NODE))
 
-/* Set the template information for an ENUMERAL_, RECORD_, or
-   UNION_TYPE to VAL.  */
+/* Set the template information for a non-alias n ENUMERAL_, RECORD_,
+   or UNION_TYPE to VAL.  ALIAS's are dealt with separately.  */
 #define SET_TYPE_TEMPLATE_INFO(NODE, VAL)				\
-  (TREE_CODE (NODE) == ENUMERAL_TYPE					\
-   || (CLASS_TYPE_P (NODE) && !TYPE_ALIAS_P (NODE))			\
-   ? (TYPE_LANG_SLOT_1 (NODE) = (VAL))				\
-   : (DECL_TEMPLATE_INFO (TYPE_NAME (NODE)) = (VAL)))
+  (gcc_checking_assert (TREE_CODE (NODE) == ENUMERAL_TYPE		\
+			|| (CLASS_TYPE_P (NODE) && !TYPE_ALIAS_P (NODE))), \
+   (TYPE_LANG_SLOT_1 (NODE) = (VAL)))					\
 
 #define TI_TEMPLATE(NODE) \
   ((struct tree_template_info*)TEMPLATE_INFO_CHECK (NODE))->tmpl
diff --git i/gcc/cp/pt.c w/gcc/cp/pt.c
index b80fe0a5cc5..ada0438f272 100644
--- i/gcc/cp/pt.c
+++ w/gcc/cp/pt.c
@@ -10088,8 +10088,26 @@  lookup_template_class_1 (tree d1, tree arglist, tree in_decl, tree context,
 	    }
 	}
 
-      // Build template info for the new specialization.
-      SET_TYPE_TEMPLATE_INFO (t, build_template_info (found, arglist));
+      /* Build template info for the new specialization.  */
+      if (TYPE_ALIAS_P (t))
+	{
+	  /* This is constructed during instantiation of the alias
+	     decl.  But for member templates of template classes, that
+	     is not correct as we need to refer to the partially
+	     instantiated template, not the most general template.
+	     The incorrect knowledge will not have escaped this
+	     instantiation process, so we're good just updating the
+	     template_info we made then.  */
+	  tree ti = DECL_TEMPLATE_INFO (TYPE_NAME (t));
+	  gcc_checking_assert (template_args_equal (TI_ARGS (ti), arglist));
+	  if (TI_TEMPLATE (ti) != found)
+	    {
+	      gcc_checking_assert (DECL_TI_TEMPLATE (found) == TI_TEMPLATE (ti));
+	      TI_TEMPLATE (ti) = found;
+	    }
+	}
+      else
+	SET_TYPE_TEMPLATE_INFO (t, build_template_info (found, arglist));
 
       elt.spec = t;
       slot = type_specializations->find_slot_with_hash (&elt, hash, INSERT);