[Bug c++/38172] warn_unused_result does not work with structs not containing a copy constructor

["jason at gcc dot gnu.org" <gcc-bugzilla at gcc dot gnu dot org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=38172

--- Comment #12 from Jason Merrill <jason at gcc dot gnu.org> ---
Author: jason
Date: Thu Apr 28 19:01:19 2016
New Revision: 235597

URL: https://gcc.gnu.org/viewcvs?rev=235597&root=gcc&view=rev
Log:
        Implement C++17 [[nodiscard]] attribute.

        PR c++/38172
        PR c++/54379
gcc/c-family/
        * c-lex.c (c_common_has_attribute): Handle nodiscard.
gcc/cp/
        * parser.c (cp_parser_std_attribute): Handle [[nodiscard]].
        * tree.c (handle_nodiscard_attribute): New.
        (cxx_attribute_table): Add [[nodiscard]].
        * cvt.c (cp_get_fndecl_from_callee, cp_get_callee_fndecl): New.
        (maybe_warn_nodiscard): New.
        (convert_to_void): Call it.

Added:
    trunk/gcc/testsuite/c-c++-common/attr-warn-unused-result.c
      - copied, changed from r235596,
trunk/gcc/testsuite/gcc.dg/attr-warn-unused-result.c
    trunk/gcc/testsuite/g++.dg/cpp1z/nodiscard1.C
    trunk/gcc/testsuite/g++.dg/cpp1z/nodiscard2.C
    trunk/gcc/testsuite/g++.dg/cpp1z/nodiscard3.C
    trunk/gcc/testsuite/g++.dg/warn/Wunused-result-2.C
Removed:
    trunk/gcc/testsuite/gcc.dg/attr-warn-unused-result.c
Modified:
    trunk/gcc/c-family/ChangeLog
    trunk/gcc/c-family/c-lex.c
    trunk/gcc/cp/ChangeLog
    trunk/gcc/cp/cp-tree.h
    trunk/gcc/cp/cvt.c
    trunk/gcc/cp/tree.c
    trunk/gcc/testsuite/g++.dg/cpp1z/feat-cxx1z.C
    trunk/gcc/testsuite/g++.dg/warn/unused-result1.C