[gcc r9-8885] c++: Avoid -Wreturn-type warning if a template fn calls noreturn template fn [PR94742]

[Jakub Jelinek <jakub@gcc.gnu.org>]

https://gcc.gnu.org/g:e9dbd80b5e62a126ccb40970f0fb233f7e0ac3a6

commit r9-8885-ge9dbd80b5e62a126ccb40970f0fb233f7e0ac3a6
Author: Jakub Jelinek <jakub@redhat.com>
Date:   Sat Apr 25 00:11:35 2020 +0200

    c++: Avoid -Wreturn-type warning if a template fn calls noreturn template fn [PR94742]
    
    finish_call_expr already has code to set current_function_returns_abnormally
    if a template calls a noreturn function, but on the following testcase it
    doesn't call a FUNCTION_DECL, but TEMPLATE_DECL instead, in which case
    we didn't check noreturn at all and just assumed it could return.
    
    2020-04-25  Jakub Jelinek  <jakub@redhat.com>
    
            PR c++/94742
            * semantics.c (finish_call_expr): When looking if all overloads
            are noreturn, use STRIP_TEMPLATE to look through TEMPLATE_DECLs.
    
            * g++.dg/warn/Wreturn-type-12.C: New test.
    
    (cherry picked from commit 4ff685a8705e8ee55fa86e75afb769ffb0975aea)

Diff:
---
 gcc/cp/semantics.c                          |  2 +-
 gcc/testsuite/g++.dg/warn/Wreturn-type-12.C | 23 +++++++++++++++++++++++
 2 files changed, 24 insertions(+), 1 deletion(-)

diff --git a/gcc/cp/semantics.c b/gcc/cp/semantics.c
index 559e38dbc14..3c578fbfa60 100644
--- a/gcc/cp/semantics.c
+++ b/gcc/cp/semantics.c
@@ -2438,7 +2438,7 @@ finish_call_expr (tree fn, vec<tree, va_gc> **args, bool disallow_virtual,
 	      bool abnormal = true;
 	      for (lkp_iterator iter (fn); abnormal && iter; ++iter)
 		{
-		  tree fndecl = *iter;
+		  tree fndecl = STRIP_TEMPLATE (*iter);
 		  if (TREE_CODE (fndecl) != FUNCTION_DECL
 		      || !TREE_THIS_VOLATILE (fndecl))
 		    abnormal = false;
diff --git a/gcc/testsuite/g++.dg/warn/Wreturn-type-12.C b/gcc/testsuite/g++.dg/warn/Wreturn-type-12.C
new file mode 100644
index 00000000000..b35d3faafb0
--- /dev/null
+++ b/gcc/testsuite/g++.dg/warn/Wreturn-type-12.C
@@ -0,0 +1,23 @@
+// PR c++/94742
+// { dg-do compile { target c++11 } }
+// { dg-options "-Wreturn-type" }
+
+template <class T>
+[[noreturn]] void
+foo (T const &t, char const *)
+{
+  throw T (t);
+}
+
+template <class U>
+int
+bar ()
+{
+  foo (42, __FUNCTION__);
+}	// { dg-bogus "no return statement in function returning non-void" }
+
+int
+main ()
+{
+  bar<long>();
+}