PR 34985 Warning "defined but not used" despite __attribute__((__used__))

["Manuel López-Ibáñez" <lopezibanez at gmail dot com>]

This patch fixes PR 34985. The problem here is that the USED flag was
not being copied from the old to the new decl when merging two decls.

Bootstrapped and regression tested on x86_64-unknown-linux-gnu.

OK to commit?

2008-07-23  Manuel Lopez-Ibanez  <manu@gcc.gnu.org

 PR 34985
 * c-decl.c (merge_decls): Merge USED flags.
cp/
 * decl.c (duplicate_decls): Merge USED flags.
testsuite/
 * gcc.dg/pr34985.c: New.
 * g++.dg/warn/pr34985.C: New

Index: gcc/testsuite/gcc.dg/pr34985.c
===================================================================
--- gcc/testsuite/gcc.dg/pr34985.c	(revision 0)
+++ gcc/testsuite/gcc.dg/pr34985.c	(revision 0)
@@ -0,0 +1,9 @@
+/* PR34985: Warning "defined but not used" despite __attribute__((__used__)) */
+/* { dg-do compile } */
+/* { dg-options "-Wall -Wextra -O2" } */
+static void xxyyzz (void);
+static void __attribute__((__used__)) xxyyzz(void)
+{
+}
+
+/* { dg-final { scan-assembler "xxyyzz" } } */
Index: gcc/testsuite/g++.dg/warn/pr34985.C
===================================================================
--- gcc/testsuite/g++.dg/warn/pr34985.C	(revision 0)
+++ gcc/testsuite/g++.dg/warn/pr34985.C	(revision 0)
@@ -0,0 +1,9 @@
+/* PR34985: Warning "defined but not used" despite __attribute__((__used__)) */
+/* { dg-do compile } */
+/* { dg-options "-Wall -Wextra -O2" } */
+static void xxyyzz (void);
+static void __attribute__((__used__)) xxyyzz(void)
+{
+}
+
+/* { dg-final { scan-assembler "xxyyzz" } } */
Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 138044)
+++ gcc/cp/decl.c	(working copy)
@@ -2055,10 +2055,16 @@ duplicate_decls (tree newdecl, tree oldd
       gcc_assert (DECL_LANG_SPECIFIC (olddecl)
 		  != DECL_LANG_SPECIFIC (newdecl));
       ggc_free (DECL_LANG_SPECIFIC (olddecl));
     }
 
+   /* Merge the USED information.  */
+   if (TREE_USED (olddecl))
+     TREE_USED (newdecl) = 1;
+   else if (TREE_USED (newdecl))
+     TREE_USED (olddecl) = 1;
+
   if (TREE_CODE (newdecl) == FUNCTION_DECL)
     {
       int function_size;
 
       function_size = sizeof (struct tree_decl_common);
Index: gcc/c-decl.c
===================================================================
--- gcc/c-decl.c	(revision 138044)
+++ gcc/c-decl.c	(working copy)
@@ -1870,10 +1870,16 @@ merge_decls (tree newdecl, tree olddecl,
 	}
     }
 
    extern_changed = DECL_EXTERNAL (olddecl) && !DECL_EXTERNAL (newdecl);
 
+   /* Merge the USED information.  */
+   if (TREE_USED (olddecl))
+     TREE_USED (newdecl) = 1;
+   else if (TREE_USED (newdecl))
+     TREE_USED (olddecl) = 1;
+
   /* Copy most of the decl-specific fields of NEWDECL into OLDDECL.
      But preserve OLDDECL's DECL_UID and DECL_CONTEXT.  */
   {
     unsigned olddecl_uid = DECL_UID (olddecl);
     tree olddecl_context = DECL_CONTEXT (olddecl);