Re: [v3 PATCH] LWG 2510, make the default constructors of library tag types explicit.

[Jonathan Wakely]

On 11/11/15 18:17 +0100, Dominique d'Humières wrote:

Revision r230175

2015-11-10  Ville Voutilainen  <ville.voutilai...@gmail.com>

    LWG 2510, make the default constructors of library tag types
    explicit.
    * include/bits/mutex.h (defer_lock_t, try_lock_t,
    adopt_lock_t): Add an explicit default constructor.
    * include/bits/stl_pair.h (piecewise_construct_t): Likewise.
    * include/bits/uses_allocator.h (allocator_arg_t): Likewise.
    * libsupc++/new (nothrow_t): Likewise.
    * testsuite/17_intro/tag_type_explicit_ctor.cc: New.

breaks bootstrap

libtool: compile:  /opt/gcc/build_w/./gcc/xgcc -shared-libgcc 
-B/opt/gcc/build_w/./gcc -nostdinc++ 
-L/opt/gcc/build_w/x86_64-apple-darwin14.5.0/libstdc++-v3/src 
-L/opt/gcc/build_w/x86_64-apple-darwin14.5.0/libstdc++-v3/src/.libs 
-L/opt/gcc/build_w/x86_64-apple-darwin14.5.0/libstdc++-v3/libsupc++/.libs 
-B/opt/gcc/gcc6w/x86_64-apple-darwin14.5.0/bin/ 
-B/opt/gcc/gcc6w/x86_64-apple-darwin14.5.0/lib/ -isystem 
/opt/gcc/gcc6w/x86_64-apple-darwin14.5.0/include -isystem 
/opt/gcc/gcc6w/x86_64-apple-darwin14.5.0/sys-include 
-I/opt/gcc/work/libstdc++-v3/../libgcc 
-I/opt/gcc/build_w/x86_64-apple-darwin14.5.0/libstdc++-v3/include/x86_64-apple-darwin14.5.0
 -I/opt/gcc/build_w/x86_64-apple-darwin14.5.0/libstdc++-v3/include 
-I/opt/gcc/work/libstdc++-v3/libsupc++ -D_GLIBCXX_SHARED 
-fno-implicit-templates -Wall -Wextra -Wwrite-strings -Wcast-qual -Wabi 
-fdiagnostics-show-location=once -fvisibility-inlines-hidden 
-ffunction-sections -fdata-sections -frandom-seed=new_handler.lo -g -O2 
-std=gnu++11 -c ../../../../work/libstdc++-v3/libsupc++/new_handler.cc  
-fno-common -DPIC -D_GLIBCXX_SHARED -o new_handler.o
../../../../work/libstdc++-v3/libsupc++/new_handler.cc:37:39: error: converting 
to 'std::nothrow_t' from initializer list would use explicit constructor 
'constexpr std::nothrow_t::nothrow_t()'
const std::nothrow_t std::nothrow = { };
                                      ^
see https://gcc.gnu.org/ml/gcc-regression/2015-11/

Fixed by this patch.


commit 97c2da9d4cc11bd5dae077ccb5fda4e72f7c34d5
Author: Jonathan Wakely <jwak...@redhat.com>
Date:   Wed Nov 11 17:27:23 2015 +0000

    	* libsupc++/new_handler.cc: Fix for explicit constructor change.

diff --git a/libstdc++-v3/libsupc++/new_handler.cc b/libstdc++-v3/libsupc++/new_handler.cc
index a09012c..4da48b3 100644
--- a/libstdc++-v3/libsupc++/new_handler.cc
+++ b/libstdc++-v3/libsupc++/new_handler.cc
@@ -34,7 +34,7 @@ namespace
 }
 #endif
 
-const std::nothrow_t std::nothrow = { };
+const std::nothrow_t std::nothrow = std::nothrow_t{ };
 
 using std::new_handler;
 namespace