[PATCH] c++: DR 1722: Make lambda to function pointer conv noexcept [PR90583]

[Marek Polacek via Gcc-patches]

DR 1722 clarifies that the conversion function from lambda to pointer to
function should be noexcept(true).

Bootstrapped/regtested on x86_64-pc-linux-gnu, ok for trunk?

gcc/cp/ChangeLog:

        PR c++/90583
        DR 1722
        * lambda.c (maybe_add_lambda_conv_op): Mark the conversion function
        as noexcept.

gcc/testsuite/ChangeLog:

        PR c++/90583
        DR 1722
        * g++.dg/cpp0x/lambda/lambda-conv14.C: New test.
---
 gcc/cp/lambda.c                                   |  2 ++
 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv14.C | 10 ++++++++++
 2 files changed, 12 insertions(+)
 create mode 100644 gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv14.C

diff --git a/gcc/cp/lambda.c b/gcc/cp/lambda.c
index c94fe8edb8e..c34d68d3da3 100644
--- a/gcc/cp/lambda.c
+++ b/gcc/cp/lambda.c
@@ -1189,6 +1189,8 @@ maybe_add_lambda_conv_op (tree type)
   tree name = make_conv_op_name (rettype);
   tree thistype = cp_build_qualified_type (type, TYPE_QUAL_CONST);
   tree fntype = build_method_type_directly (thistype, rettype, void_list_node);
+  /* DR 1722: The conversion function should be noexcept.  */
+  fntype = build_exception_variant (fntype, noexcept_true_spec);
   tree convfn = build_lang_decl (FUNCTION_DECL, name, fntype);
   SET_DECL_LANGUAGE (convfn, lang_cplusplus);
   tree fn = convfn;
diff --git a/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv14.C 
b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv14.C
new file mode 100644
index 00000000000..869e0d51d2b
--- /dev/null
+++ b/gcc/testsuite/g++.dg/cpp0x/lambda/lambda-conv14.C
@@ -0,0 +1,10 @@
+// PR c++/90583
+// DR 1722: Lambda to function pointer conversion should be noexcept.
+// { dg-do compile { target c++11 } }
+
+void
+foo ()
+{
+  auto l = [](int){ return 42; };
+  static_assert(noexcept((int (*)(int))(l)), "");
+}

base-commit: b0c990f2661a2979c68c840781847efe27a0779b
-- 
2.26.2