[Bug libstdc++/65393] New: std::thread shared_ptr inefficiency

[klemensbaum at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=65393

Bug ID: 65393
   Summary: std::thread shared_ptr inefficiency
   Product: gcc
   Version: unknown
Status: UNCONFIRMED
  Severity: enhancement
  Priority: P3
 Component: libstdc++
  Assignee: unassigned at gcc dot gnu.org
  Reporter: klemensbaum at gmail dot com

The std::thread implementation passes around shared_ptr instances by value in
multiple places where they could be moved:

1)
in the function
  void
  thread::_M_start_thread(__shared_base_type __b)

the line
_M_start_thread(__b, nullptr);

could be changed to
_M_start_thread(std::move(__b), nullptr);

or alternatively take __shared_base_type by universal reference and forward
it into the other _M_start_thread overload.

2)
in the function 
  void
  thread::_M_start_thread(__shared_base_type __b, void (*)())

the lines
__b-_M_this_ptr = __b;
int __e = __gthread_create(_M_id._M_thread,
   execute_native_thread_routine, __b.get());
could be changed to
auto __p = __b.get();
__b-_M_this_ptr = std::move(__b);
int __e = __gthread_create(_M_id._M_thread,
   execute_native_thread_routine, __p);

3) Finally, the use of shared_ptr seems wholly unnecessarily. This can likely
be implemented more cleanly with unique_ptr, and more efficiently, since it
avoids the extra heap space for the reference count and all of the atomic ops.

[Bug c++/56090] New: Injected-class-name treated as constructor name

[klemensbaum at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56090

 Bug #: 56090
   Summary: Injected-class-name treated as constructor name
Classification: Unclassified
   Product: gcc
   Version: 4.7.1
Status: UNCONFIRMED
  Severity: normal
  Priority: P3
 Component: c++
AssignedTo: unassig...@gcc.gnu.org
ReportedBy: klemensb...@gmail.com


should compile, see ISO/IEC 14882:2011 §9.0.2


$ cat test.cpp
struct foo { foo::foo::foo::foo::foo::foo* bar; };

$ g++ test.cpp 
test.cpp:1:14: error: ‘foo::foo’ names the constructor, not the type

$ g++ -v
Using built-in specs.
COLLECT_GCC=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1/g++
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.7.1/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /var/tmp/portage/sys-devel/gcc-4.7.1/work/gcc-4.7.1/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.1
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.1/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --without-ppl --without-cloog --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --enable-multilib
--with-multilib-list=m32,m64 --enable-libmudflap --disable-libssp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.7.1/python
--enable-checking=release --disable-libgcj --enable-languages=c,c++,fortran
--enable-shared --enable-threads=posix --enable-__cxa_atexit
--enable-clocale=gnu --enable-targets=all --with-bugurl=http://bugs.gentoo.org/
--with-pkgversion='Gentoo 4.7.1 p1.0, pie-0.5.3'
Thread model: posix
gcc version 4.7.1 (Gentoo 4.7.1 p1.0, pie-0.5.3)

[Bug c++/56090] Injected-class-name treated as constructor name

[klemensbaum at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56090



--- Comment #3 from Klemens klemensbaum at gmail dot com 2013-01-23 22:32:47 
UTC ---

I would argue that in 3.4.3.1.2 the constructor is not an acceptable lookup

result, since it would result in the code being invalid.





Additionally, the following use of a type alias (where the constructor is

clearly not an acceptable lookup result) does not compile on my g++-4.7.1:

struct foo { using bar = foo::foo::foo; };