[Bug c++/59329] Using `assert(...)` is not allowed in constexpr functions

["lucdanton at free dot fr" <gcc-bugzilla@gcc.gnu.org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=59329

lucdanton at free dot fr changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |lucdanton at free dot fr

--- Comment #2 from lucdanton at free dot fr ---
As a workaround I thought about (ab)using the comma operator:

    return assert( cond ), expr;

The reasoning being that C guarantees that assert(…) is a void expression
(regardless of NDEBUG). This is rejected as well, although I’m not entirely
sure why. After a quick look at the preprocessed source, it appears GCC rejects
(‘body not a return statement’, again) functions of the form:

//------

void some_extern_func();

constexpr int foo(int i)
{ return (true ? static_cast<void>(0) : some_extern_func()), i; }

//-----

If the third leg of the conditional operator is e.g. throw whatever (a common
trick to ‘halt’ CTFE) everything behaves as expected.

Does this warrant opening another bug?
>From gcc-bugs-return-441337-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Thu Jan 23 17:18:12 2014
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From: "redi at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug libstdc++/59872] [4.9 Regression] Cannot move std::map with move-only mapped_type
Date: Thu, 23 Jan 2014 17:18:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idY872

--- Comment #9 from Jonathan Wakely <redi at gcc dot gnu.org> ---
Author: redi
Date: Thu Jan 23 17:17:04 2014
New Revision: 206994

URL: http://gcc.gnu.org/viewcvs?rev 6994&root=gcc&view=rev
Log:
    PR libstdc++/59872
    * include/bits/stl_map.h (map::operator=(map&&)): Fix comment.
    * include/bits/stl_multimap.h (multimap::operator=(multimap&&)):
    Likewise.
    * include/bits/stl_multiset.h (multiset::operator=(multiset&&)):
    Likewise.
    * include/bits/stl_set.h (set::operator=(set&&)): Likewise.
    * include/bits/stl_tree.h (_Rb_tree::_M_move_data): New overloaded
    functions to perform moving or copying of elements from rvalue tree.
    (_Rb_tree::_Rb_tree(_Rb_tree&&)): Use _M_move_data.
    (_Rb_tree::_Rb_tree(_Rb_tree&&, _Node_allocator&&)): Likewise.
    * testsuite/23_containers/map/59872.cc: New.
    * testsuite/23_containers/map/56613.cc: Remove duplicate include.

Added:
    trunk/libstdc++-v3/testsuite/23_containers/map/59872.cc
Modified:
    trunk/libstdc++-v3/ChangeLog
    trunk/libstdc++-v3/include/bits/stl_map.h
    trunk/libstdc++-v3/include/bits/stl_multimap.h
    trunk/libstdc++-v3/include/bits/stl_multiset.h
    trunk/libstdc++-v3/include/bits/stl_set.h
    trunk/libstdc++-v3/include/bits/stl_tree.h
    trunk/libstdc++-v3/testsuite/23_containers/map/56613.cc