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[C++] template specializations

Message ID 23c6cd3c-51ed-f0d7-27a4-9092e6b84939@acm.org
State New
Headers show
Series [C++] template specializations | expand

Commit Message

Nathan Sidwell May 28, 2019, 5:03 p.m. UTC 
In tracking a surprise on the modules branch, I came across this code in 
duplicate decls.  Why would the newly minted decl already have 
specializations?  That smells wrong.

This chainon call was added by Mark Mitchell back in 1998, (rev 21876) 
to deal with template friends of templates.  Since that time we've 
cleaned a lot of that code up, and in particular do not push the friend 
template until instantiation time.  I believe these changes make this 
chainon unneeded.

This patch changes it to assert there aren't any such specializations to 
concatenate.  I'm putting this on trunk to give it wider exposure than I 
can on the modules branch.  It has survived bootstrap on x86_64-linux.

nathan
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Patch

2019-05-28  Nathan Sidwell  <nathan@acm.org>

	* decl.c (duplicate_decls): Assert a template newdecl has no
	specializations.

Index: cp/decl.c
===================================================================
--- cp/decl.c	(revision 271712)
+++ cp/decl.c	(working copy)
@@ -2026,7 +2026,8 @@  duplicate_decls (tree newdecl, tree oldd
       tree new_result = DECL_TEMPLATE_RESULT (newdecl);
       TREE_TYPE (olddecl) = TREE_TYPE (old_result);
-      DECL_TEMPLATE_SPECIALIZATIONS (olddecl)
-	= chainon (DECL_TEMPLATE_SPECIALIZATIONS (olddecl),
-		   DECL_TEMPLATE_SPECIALIZATIONS (newdecl));
+
+      /* The new decl should not already have gathered any
+	 specializations.  */
+      gcc_assert (!DECL_TEMPLATE_SPECIALIZATIONS (newdecl));
 
       DECL_ATTRIBUTES (old_result)