Patchwork C++ PATCH for c++/49251 (bogus unused warning with empty argument pack)

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Submitter Jason Merrill
Date June 16, 2011, 9:47 p.m.
Message ID <4DFA79E2.2020909@redhat.com>
Download mbox | patch
Permalink /patch/100730/
State New
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Comments

Jason Merrill - June 16, 2011, 9:47 p.m.
We normally mark variables as used in finish_id_expression, but we 
weren't doing that for variables with dependent type.  They're still 
used even if we don't know what type they will have when instantiated.

Tested x86_64-pc-linux-gnu, applying to trunk.

Patch

commit b2f47a386f7f605829f4f1f30d2c1d8e254ff9d7
Author: Jason Merrill <jason@redhat.com>
Date:   Wed Jun 15 13:32:16 2011 -0400

    	PR c++/49251
    	* semantics.c (finish_id_expression): Mark even dependent
    	variables as used.

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 55f9519..bad7acb 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -3196,7 +3196,10 @@  finish_id_expression (tree id_expression,
 	     (or an instantiation thereof).  */
 	  if (TREE_CODE (decl) == VAR_DECL
 	      || TREE_CODE (decl) == PARM_DECL)
-	    return convert_from_reference (decl);
+	    {
+	      mark_used (decl);
+	      return convert_from_reference (decl);
+	    }
 	  /* The same is true for FIELD_DECL, but we also need to
 	     make sure that the syntax is correct.  */
 	  else if (TREE_CODE (decl) == FIELD_DECL)
diff --git a/gcc/testsuite/g++.dg/cpp0x/variadic113.C b/gcc/testsuite/g++.dg/cpp0x/variadic113.C
new file mode 100644
index 0000000..3f1bb2a
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/variadic113.C
@@ -0,0 +1,20 @@ 
+// PR c++/49251
+// { dg-options "-std=c++0x -Wunused-parameter" }
+
+struct A {};
+template <int> int f(A);
+
+template< int... Indices >
+struct indices {};
+
+template< class... Args >
+void sink( Args&&... ) {}
+
+template< class T, int... Indices >
+void unpack_test( T && t, indices<Indices...> ) {
+  sink( f<Indices>(t)... );
+}
+
+int main() {
+  unpack_test( A(), indices<>() );
+}