[PATCH] restore -Wunused-variable on a typedef'd variable in a function template (PR 79548)

[Martin Sebor <msebor at gmail dot com>]

The attached patch fixes bug 79548 - [5/6/7 Regression] missing
-Wunused-variable on a typedef'd variable in a function template,
most likely broken by the introduction of -Wunused-local-typedefs.

While testing the patch I came across a couple of other bugs:

  79585 - spurious -Wunused-variable on a pointer with attribute
          unused in function template
and

  79586 - missing -Wdeprecated depending on position of attribute

The test I added for 79548 fails two assertions due to the first
of these two so I xfailed them.  The second doesn't have an impact
on it.  Neither of these is a regression so I didn't try to fix them.

Martin

PR c++/79548 - [5/6/7 Regression] missing -Wunused-variable on a typedef'd variable in a function template

gcc/cp/ChangeLog:

	PR c++/79548
	* decl.c (poplevel): Avoid diagnosing entities declared with
	attribute unused.
	(initialize_local_var): Do not consider the type of a variable
	when determining whether or not it's used.
	
gcc/testsuite/ChangeLog:

	PR c++/79548
	* g++.dg/warn/Wunused-var-26.C: New test.

diff --git a/gcc/cp/decl.c b/gcc/cp/decl.c
index 70c44fb..e315ad0 100644
--- a/gcc/cp/decl.c
+++ b/gcc/cp/decl.c
@@ -664,7 +664,8 @@ poplevel (int keep, int reverse, int functionbody)
 	    && (!CLASS_TYPE_P (type)
 		|| !TYPE_HAS_NONTRIVIAL_DESTRUCTOR (type)
 		|| lookup_attribute ("warn_unused",
-				     TYPE_ATTRIBUTES (TREE_TYPE (decl)))))
+				     TYPE_ATTRIBUTES (TREE_TYPE (decl))))
+	    && !lookup_attribute ("unused", TYPE_ATTRIBUTES (TREE_TYPE (decl))))
 	  {
 	    if (! TREE_USED (decl))
 	      warning_at (DECL_SOURCE_LOCATION (decl),
@@ -6546,7 +6547,6 @@ initialize_local_var (tree decl, tree init)
 {
   tree type = TREE_TYPE (decl);
   tree cleanup;
-  int already_used;
 
   gcc_assert (VAR_P (decl)
 	      || TREE_CODE (decl) == RESULT_DECL);
@@ -6564,7 +6564,7 @@ initialize_local_var (tree decl, tree init)
     return;
 
   /* Compute and store the initial value.  */
-  already_used = TREE_USED (decl) || TREE_USED (type);
+  bool already_used = TREE_USED (decl);
   if (TREE_USED (type))
     DECL_READ_P (decl) = 1;
 
diff --git a/gcc/testsuite/g++.dg/warn/Wunused-var-26.C b/gcc/testsuite/g++.dg/warn/Wunused-var-26.C
new file mode 100644
index 0000000..562f25b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wunused-var-26.C
@@ -0,0 +1,127 @@
+// PR c++/79548 - missing -Wunused-variable on a typedef'd variable
+// in a function template
+// { dg-do compile }
+// { dg-options "-Wunused" }
+
+
+#define UNUSED __attribute__ ((unused))
+
+template <class T>
+void f_int ()
+{
+  T t;                        // { dg-warning "unused variable" }
+
+  typedef T U;
+  U u;                        // { dg-warning "unused variable" }
+}
+
+template void f_int<int>();
+
+
+template <class T>
+void f_intptr ()
+{
+  T *t = 0;                   // { dg-warning "unused variable" }
+
+  typedef T U;
+  U *u = 0;                   // { dg-warning "unused variable" }
+}
+
+template void f_intptr<int>();
+
+
+template <class T>
+void f_var_unused ()
+{
+  // The variable is marked unused.
+  T t UNUSED;
+
+  typedef T U;
+  U u UNUSED;
+}
+
+template void f_var_unused<int>();
+
+
+template <class T>
+void f_var_type_unused ()
+{
+  // The variable's type is marked unused.
+  T* UNUSED t = new T;   // { dg-bogus "unused variable" "bug 79585" { xfail *-*-* } }
+
+  typedef T U;
+  U* UNUSED u = new U;   // { dg-bogus "unused variable" "bug 79585" { xfail *-*-* } }
+
+  typedef T UNUSED U;
+  U v = U ();   // { dg-bogus "unused variable" "bug 79585" { xfail *-*-* } }
+}
+
+template void f_var_type_unused<int>();
+
+
+struct A { int i; };
+
+template <class T>
+void f_A ()
+{
+  T t;                        // { dg-warning "unused variable" }
+
+  typedef T U;
+  U u;                        // { dg-warning "unused variable" }
+}
+
+template void f_A<A>();
+
+
+template <class T>
+void f_A_unused ()
+{
+  T t UNUSED;
+
+  typedef T U;
+  U u UNUSED;
+}
+
+template void f_A_unused<A>();
+
+
+struct B { B (); };
+
+template <class T>
+void f_B ()
+{
+  T t;
+
+  typedef T U;
+  U u;
+}
+
+template void f_B<B>();
+
+
+struct C { ~C (); };
+
+template <class T>
+void f_C ()
+{
+  T t;
+
+  typedef T U;
+  U u;
+}
+
+template void f_C<C>();
+
+
+struct D { B b; };
+
+template <class T>
+void f_D ()
+{
+  T t;
+
+  typedef T U;
+  U u;
+}
+
+template void f_D<D>();