[PATCH] merge attributes from function template redeclarations (PR 84294)

[Martin Sebor <msebor at gmail dot com>]

Attached is a patch for the failure to merge a subset of attributes
specified on redeclarations of a function template with those of
the first declaration (const, malloc, pure, noinline, noreturn,
and nothrow).  This was uncovered this morning while debugging
failures in tests I added just yesterday and although it's not
a regression I figured since I introduced the test failures and
the fix appears easy it might as well be taken care of now.

The test I added for this exposed a subtle bug in -Wreturn-type
where the warning triggers on a function template instantiated
on a noreturn function even though the middle end successfully
eliminates statements after the noreturn call.  This is not
a regression either so to avoid mission creep I just xfailed
the test and opened bug 84621 to remind us to fix it in
the future.

Bootstrap passes, a full regression test suite run is underway.

Martin

PR c++/84294 - attributes on a function template redeclaration silently discarded

gcc/cp/ChangeLog:

	PR c++/84294
	* decl.c (check_redeclaration_no_default_args): Merge attributes
	specified on redeclarations of the same function template.

gcc/testsuite/ChangeLog:

	PR c++/84294
	* g++.dg/ext/attr-const.C: Remove xfail.
	* g++.dg/ext/attr-malloc-3.C: New test.
	* g++.dg/ext/attr-noinline-3.C: New test.
	* g++.dg/ext/attr-noreturn-3.C: New test.
	* g++.dg/ext/attr-nothrow-3.C: New test.
	* g++.dg/ext/attr-pure.C: Remove xfail.

Index: gcc/cp/decl.c
===================================================================
--- gcc/cp/decl.c	(revision 258077)
+++ gcc/cp/decl.c	(working copy)
@@ -1355,6 +1355,26 @@ check_redeclaration_no_default_args (tree decl)
       }
 }
 
+/* Merge tree bits that correspond to attributes noreturn, nothrow,
+   const,  malloc, and pure from NEWDECL with those of OLDDECL.  */
+
+static void
+merge_attribute_bits (tree newdecl, tree olddecl)
+{
+  TREE_THIS_VOLATILE (newdecl) |= TREE_THIS_VOLATILE (olddecl);
+  TREE_THIS_VOLATILE (olddecl) |= TREE_THIS_VOLATILE (newdecl);
+  TREE_NOTHROW (newdecl) |= TREE_NOTHROW (olddecl);
+  TREE_NOTHROW (olddecl) |= TREE_NOTHROW (newdecl);
+  TREE_READONLY (newdecl) |= TREE_READONLY (olddecl);
+  TREE_READONLY (olddecl) |= TREE_READONLY (newdecl);
+  DECL_IS_MALLOC (newdecl) |= DECL_IS_MALLOC (olddecl);
+  DECL_IS_MALLOC (olddecl) |= DECL_IS_MALLOC (newdecl);
+  DECL_PURE_P (newdecl) |= DECL_PURE_P (olddecl);
+  DECL_PURE_P (olddecl) |= DECL_PURE_P (newdecl);
+  DECL_UNINLINABLE (newdecl) |= DECL_UNINLINABLE (olddecl);
+  DECL_UNINLINABLE (olddecl) |= DECL_UNINLINABLE (newdecl);
+}
+
 #define GNU_INLINE_P(fn) (DECL_DECLARED_INLINE_P (fn)			\
 			  && lookup_attribute ("gnu_inline",		\
 					       DECL_ATTRIBUTES (fn)))
@@ -2048,6 +2068,8 @@ next_arg:;
 	      DECL_DISREGARD_INLINE_LIMITS (old_result)
 	        |= DECL_DISREGARD_INLINE_LIMITS (new_result);
 	      check_redeclaration_exception_specification (newdecl, olddecl);
+
+	      merge_attribute_bits (new_result, old_result);
 	    }
 	}
 
@@ -2228,18 +2250,7 @@ next_arg:;
 	    |= DECL_LOOPING_CONST_OR_PURE_P (olddecl);
 
 	  if (merge_attr)
-	    {
-	      TREE_THIS_VOLATILE (newdecl) |= TREE_THIS_VOLATILE (olddecl);
-	      TREE_THIS_VOLATILE (olddecl) |= TREE_THIS_VOLATILE (newdecl);
-	      TREE_NOTHROW (newdecl) |= TREE_NOTHROW (olddecl);
-	      TREE_NOTHROW (olddecl) |= TREE_NOTHROW (newdecl);
-	      TREE_READONLY (newdecl) |= TREE_READONLY (olddecl);
-	      TREE_READONLY (olddecl) |= TREE_READONLY (newdecl);
-	      DECL_IS_MALLOC (newdecl) |= DECL_IS_MALLOC (olddecl);
-	      DECL_IS_MALLOC (olddecl) |= DECL_IS_MALLOC (newdecl);
-	      DECL_PURE_P (newdecl) |= DECL_PURE_P (olddecl);
-	      DECL_PURE_P (olddecl) |= DECL_PURE_P (newdecl);
-	    }
+	    merge_attribute_bits (newdecl, olddecl);
 	  else
 	    {
 	      /* Merge the noreturn bit.  */
Index: gcc/testsuite/g++.dg/ext/attr-const.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-const.C	(revision 258077)
+++ gcc/testsuite/g++.dg/ext/attr-const.C	(working copy)
@@ -68,6 +68,5 @@ void test_fnone_const ()
   if (i0 != i1)
     templ_none_const_failed ();
 
-  // The following fails (most likely) due to bug 84294.
-  // { dg-final { scan-tree-dump-not "templ_none_const_failed" "optimized" { xfail *-*-* } } }
+  // { dg-final { scan-tree-dump-not "templ_none_const_failed" "optimized" } }
 }
Index: gcc/testsuite/g++.dg/ext/attr-malloc-3.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-malloc-3.C	(revision 258077)
+++ gcc/testsuite/g++.dg/ext/attr-malloc-3.C	(working copy)
@@ -91,7 +91,6 @@ void test_templ_none_malloc (void)
   if (p == a)                       // must be false
     templ_none_malloc_failed ();    // should be eliminated
 
-  // The following fails (most likely) due to bug 84294.
   // Verify that the call to templ_none_malloc_failed() is eliminated.
-  // { dg-final { scan-tree-dump-not "templ_none_malloc_failed" "optimized" { xfail *-*-* } } }
+  // { dg-final { scan-tree-dump-not "templ_none_malloc_failed" "optimized" } }
 }
Index: gcc/testsuite/g++.dg/ext/attr-noinline-3.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-noinline-3.C	(nonexistent)
+++ gcc/testsuite/g++.dg/ext/attr-noinline-3.C	(working copy)
@@ -0,0 +1,45 @@
+/*  PR c++/84294 - attributes on a function template redeclaration silently
+    discarded
+    { dg-do compile }
+    { dg-options "-O -fdump-tree-optimized" } */
+
+template <void test ()>
+void test_func ()
+{
+  test ();
+}
+
+int x;
+
+void __attribute__ ((noinline)) func_noinline_none ();
+void func_noinline_none () { x = __LINE__; }
+
+template void test_func<func_noinline_none>();
+// { dg-final { scan-tree-dump-times "func_noinline_none *\\(\\);" 1 "optimized" } }
+
+
+void func_none_noinline ();
+void  __attribute__ ((noinline)) func_none_noinline () { x = __LINE__; }
+
+template void test_func<func_none_noinline>();
+// { dg-final { scan-tree-dump-times "func_none_noinline *\\(\\);" 1 "optimized" } }
+
+
+template <class>
+void __attribute__ ((noinline)) templ_noinline_none () { x = __LINE__; }
+
+template <class>
+void templa_noinline_none ();
+
+template void test_func<templ_noinline_none<int> >();
+// { dg-final { scan-tree-dump-times "templ_noinline_none<int> *\\(\\);" 1 "optimized" } }
+
+
+template <class>
+void templ_none_noinline ();
+
+template <class>
+void  __attribute__ ((noinline)) templ_none_noinline () { x = __LINE__; }
+
+template void test_func<templ_none_noinline<int> >();
+// { dg-final { scan-tree-dump-times "templ_none_noinline<int> *\\(\\);" 1 "optimized" } }
Index: gcc/testsuite/g++.dg/ext/attr-noreturn-3.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-noreturn-3.C	(nonexistent)
+++ gcc/testsuite/g++.dg/ext/attr-noreturn-3.C	(working copy)
@@ -0,0 +1,54 @@
+/*  PR c++/84294 - attributes on a function template redeclaration silently
+    discarded
+    { dg-do compile }
+    { dg-options "-O -fdump-tree-optimized" } */
+
+typedef void Func ();
+
+template <Func>
+void fail_func ();
+
+template <Func test>
+int test_func ()
+{
+  test ();
+
+  // Should be eliminated.
+  fail_func<test> ();
+
+  // Expect no -Wreturn type here despite the absence of a return
+  // statement in a non-void function.
+}   // { dg-bogus "\\\[-Wreturn-type]" "bug 84621" { xfail *-*-* } }
+
+void __attribute__ ((noreturn)) func_noreturn_none ();
+void func_noreturn_none ();
+
+template int test_func<func_noreturn_none>();
+
+
+void func_none_noreturn ();
+void  __attribute__ ((noreturn)) func_none_noreturn ();
+
+template int test_func<func_none_noreturn>();
+
+
+template <class>
+void __attribute__ ((noreturn)) templ_noreturn_none ();
+
+template <class>
+void templa_noreturn_none ();
+
+template int test_func<templ_noreturn_none<int> >();
+
+
+template <class>
+void templ_none_noreturn ();
+
+template <class>
+void  __attribute__ ((noreturn)) templ_none_noreturn ();
+
+template int test_func<templ_none_noreturn<int> >();
+
+
+// Verify that calls to fail_func() specializations have been eliminated.
+// { dg-final { scan-tree-dump-not "fail_func" "optimized" } }
Index: gcc/testsuite/g++.dg/ext/attr-nothrow-3.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-nothrow-3.C	(nonexistent)
+++ gcc/testsuite/g++.dg/ext/attr-nothrow-3.C	(working copy)
@@ -0,0 +1,60 @@
+/*  PR c++/84294 - attributes on a function template redeclaration silently
+    discarded
+    { dg-do compile }
+    { dg-options "-O -fdump-tree-eh -fdump-tree-optimized" } */
+
+typedef void Func ();
+
+template <Func>
+void fail_func () throw ();
+
+template <Func test>
+void test_func () throw ()
+{
+  try
+    {
+      test ();
+    }
+  catch (...)
+    {
+      // Should be eliminated.
+      fail_func<test> ();
+    }
+}
+
+void __attribute__ ((nothrow)) func_nothrow_none ();
+void func_nothrow_none ();
+
+template void test_func<func_nothrow_none>();
+
+
+void func_none_nothrow ();
+void  __attribute__ ((nothrow)) func_none_nothrow ();
+
+template void test_func<func_none_nothrow>();
+
+
+template <class>
+void __attribute__ ((nothrow)) templ_nothrow_none ();
+
+template <class>
+void templa_nothrow_none ();
+
+template void test_func<templ_nothrow_none<int> >();
+
+
+template <class>
+void templ_none_nothrow ();
+
+template <class>
+void  __attribute__ ((nothrow)) templ_none_nothrow ();
+
+template void test_func<templ_none_nothrow<int> >();
+
+
+// Verify that no exception handling code was emitted.
+// { dg-final { scan-tree-dump-not "eh_dispatch" "eh" } }
+// { dg-final { scan-tree-dump-not "resx" "eh" } }
+
+// Verify that calls to fail_func() specializations have been eliminated.
+// { dg-final { scan-tree-dump-not "fail_func" "optimized" } }
Index: gcc/testsuite/g++.dg/ext/attr-pure.C
===================================================================
--- gcc/testsuite/g++.dg/ext/attr-pure.C	(revision 258077)
+++ gcc/testsuite/g++.dg/ext/attr-pure.C	(working copy)
@@ -69,6 +69,5 @@ void test_fnone_const ()
   if (i0 != i1)
     templ_none_const_failed ();
 
-  // The following fails (most likely) due to bug 84294.
-  // { dg-final { scan-tree-dump-not "templ_none_const_failed" "optimized" { xfail *-*-* } } }
+  // { dg-final { scan-tree-dump-not "templ_none_const_failed" "optimized" } }
 }