c++: typedef for linkage [PR 99208]

Message ID a105ef54-c429-4eae-245b-398898ab9fdc@acm.org
State New
Headers show
  • c++: typedef for linkage [PR 99208]
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Commit Message

Nathan Sidwell Feb. 23, 2021, 3:17 p.m.
Unnamed	types with a typedef name for linkage were always troublesome in 
modules.  This is the underlying cause of that trouble -- we	were 
creating incorrect type structures.  Classes have an implicit 
self-reference, and we created that for unnamed classes too.  It turns 
out we make use of this member, so just not generating it turned into a 
rathole.  This member is created using the anonymous name -- because 
we've not yet met the typedef name.  When we retrofit the typedef name 
we were checking identifier matching and changing all type variants with 
that identifier.  Which meant we ended up with a strange typedef for the 
self reference.  This fixes things to check for DECL identity of the 
variants, so we don't smash the self-reference -- that continues to have 
the anonymous name.

         PR c++/99208
         * decl.c (name_unnamed_type): Check DECL identity, not IDENTIFIER
         * g++.dg/modules/pr99208_a.C: New.
         * g++.dg/modules/pr99208_b.C: New.

Nathan Sidwell


diff --git c/gcc/cp/decl.c w/gcc/cp/decl.c
index 7fa8f52d667..1742e286d9f 100644
--- c/gcc/cp/decl.c
+++ w/gcc/cp/decl.c
@@ -11081,21 +11081,18 @@  name_unnamed_type (tree type, tree decl)
   gcc_assert (TYPE_UNNAMED_P (type));
-  /* Replace the anonymous name with the real name everywhere.  */
+  /* Replace the anonymous decl with the real decl.  Be careful not to
+     rename other typedefs (such as the self-reference) of type.  */
+  tree orig = TYPE_NAME (type);
   for (tree t = TYPE_MAIN_VARIANT (type); t; t = TYPE_NEXT_VARIANT (t))
-      /* We do not rename the debug info representing the unnamed
-	 tagged type because the standard says in [dcl.typedef] that
-	 the naming applies only for linkage purposes.  */
-      /*debug_hooks->set_name (t, decl);*/
+    if (TYPE_NAME (t) == orig)
       TYPE_NAME (t) = decl;
   /* If this is a typedef within a template class, the nested
      type is a (non-primary) template.  The name for the
      template needs updating as well.  */
-      = TYPE_IDENTIFIER (type);
   /* Adjust linkage now that we aren't unnamed anymore.  */
   reset_type_linkage (type);
diff --git c/gcc/testsuite/g++.dg/modules/pr99208_a.C w/gcc/testsuite/g++.dg/modules/pr99208_a.C
new file mode 100644
index 00000000000..427c7f1b04c
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99208_a.C
@@ -0,0 +1,9 @@ 
+// PR 99208 typedef anonymous class
+// { dg-additional-options {-Wno-pedantic -fmodules-ts} }
+# 5 "pr99208_a.C" 1
+typedef struct {} __mbstate_t;
+# 7 "" 2
+export module hello:format;
+// { dg-module-cmi {hello:format} }
+export __mbstate_t v;
diff --git c/gcc/testsuite/g++.dg/modules/pr99208_b.C w/gcc/testsuite/g++.dg/modules/pr99208_b.C
new file mode 100644
index 00000000000..0ed68d8069a
--- /dev/null
+++ w/gcc/testsuite/g++.dg/modules/pr99208_b.C
@@ -0,0 +1,4 @@ 
+// { dg-additional-options {-fmodules-ts} }
+export module hello;
+// { dg-module-cmi hello }
+export import :format;