[Bug c++/57437] New: C++11: mutable lambdas; gcc 4.7-4.8

[Bug c++/57437] New: C++11: mutable lambdas; gcc 4.7-4.8

[alxchk at alxchk dot me]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57437

            Bug ID: 57437
           Summary: C++11: mutable lambdas; gcc 4.7-4.8
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: alxchk at alxchk dot me

> cat test.cpp
#include <vector>
#include <iostream>

int main(int argc, char *argv[])
{
  auto x = std::vector<int>({1, 2, 3});

  auto y = [x] () 
    mutable {
    for (auto &i: x)
      i ++;
    return x;
  };

  for (const auto &i: y())
    std::cout << i << std::endl;

  for (const auto &i: y())
    std::cout << i << std::endl;

  return 0;
}

> x86_64-pc-linux-gnu-g++-4.6.3 -o test test.cpp -std=gnu++0x
> ./test
2
3
4
3
4
5
> LC_ALL=C x86_64-pc-linux-gnu-g++-4.6.3 -v 
Using built-in specs.
COLLECT_GCC=x86_64-pc-linux-gnu-g++-4.6.3
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.6.3/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/portage/sys-devel/gcc-4.6.3/work/gcc-4.6.3/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.6.3
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.6.3/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --with-ppl --with-cloog --disable-ppl-version-check
--with-cloog-include=/usr/include/cloog-ppl --enable-lto --enable-nls
--without-included-gettext --with-system-zlib --enable-obsolete
--disable-werror --enable-secureplt --enable-multilib --enable-libmudflap
--disable-libssp --enable-esp --enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.6.3/python
--enable-checking=release --disable-libgcj --enable-libstdcxx-time
--enable-languages=c,c++,objc,fortran --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened 4.6.3
p1.11, pie-0.5.2'
Thread model: posix
gcc version 4.6.3 (Gentoo Hardened 4.6.3 p1.11, pie-0.5.2)


> x86_64-pc-linux-gnu-g++-4.7.2 -o test2 test.cpp -std=gnu++0x 
> ./test2
2
3
4

> LC_ALL=C x86_64-pc-linux-gnu-g++-4.7.2 -v     
Using built-in specs.
COLLECT_GCC=x86_64-pc-linux-gnu-g++-4.7.2
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.7.2/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with:
/var/tmp/portage/portage/sys-devel/gcc-4.7.2-r1/work/gcc-4.7.2/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.7.2
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.2/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.2
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.2/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.7.2/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.7.2/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --with-ppl --with-cloog --disable-ppl-version-check
--with-cloog-include=/usr/include/cloog-ppl --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-esp
--enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.7.2/python
--enable-checking=release --disable-libgcj --enable-libstdcxx-time
--enable-languages=c,c++,objc,fortran --enable-shared --enable-threads=posix
--enable-__cxa_atexit --enable-clocale=gnu --enable-targets=all
--with-bugurl=http://bugs.gentoo.org/ --with-pkgversion='Gentoo Hardened
4.7.2-r1 p1.5, pie-0.5.5'
Thread model: posix
gcc version 4.7.2 (Gentoo Hardened 4.7.2-r1 p1.5, pie-0.5.5)

> x86_64-pc-linux-gnu-g++-4.8.0 -o test test.cpp -std=gnu++11
> ./test
2
3
4

> LC_ALL=C x86_64-pc-linux-gnu-g++-4.8.0 -v
Using built-in specs.
COLLECT_GCC=x86_64-pc-linux-gnu-g++-4.8.0
COLLECT_LTO_WRAPPER=/usr/libexec/gcc/x86_64-pc-linux-gnu/4.8.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: /tmp/portage/sys-devel/gcc-4.8.0/work/gcc-4.8.0/configure
--prefix=/usr --bindir=/usr/x86_64-pc-linux-gnu/gcc-bin/4.8.0
--includedir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.0/include
--datadir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.0
--mandir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.0/man
--infodir=/usr/share/gcc-data/x86_64-pc-linux-gnu/4.8.0/info
--with-gxx-include-dir=/usr/lib/gcc/x86_64-pc-linux-gnu/4.8.0/include/g++-v4
--host=x86_64-pc-linux-gnu --build=x86_64-pc-linux-gnu --disable-altivec
--disable-fixed-point --with-ppl --with-cloog --disable-isl-version-check
--with-cloog --enable-lto --enable-nls --without-included-gettext
--with-system-zlib --enable-obsolete --disable-werror --enable-secureplt
--enable-multilib --with-multilib-list=m32,m64 --disable-libmudflap
--disable-libssp --enable-esp --enable-libgomp
--with-python-dir=/share/gcc-data/x86_64-pc-linux-gnu/4.8.0/python
--enable-checking=release --disable-libgcj --enable-libstdcxx-time
--disable-libquadmath --enable-languages=c,c++ --enable-shared
--enable-threads=posix --enable-__cxa_atexit --enable-clocale=gnu
--enable-targets=all --with-bugurl=http://bugs.gentoo.org/
--with-pkgversion='Gentoo Hardened 4.8.0 p1.2, pie-0.5.5'
Thread model: posix
gcc version 4.8.0 (Gentoo Hardened 4.8.0 p1.2, pie-0.5.5)

[Bug c++/57437] C++11: mutable lambdas; gcc 4.7-4.8

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57437

Daniel Krügler <daniel.kruegler at googlemail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler@googlemail.
                   |                            |com

--- Comment #1 from Daniel Krügler <daniel.kruegler at googlemail dot com> ---
I can confirm the problem for my mingw-64-bit system using gcc 4.9.0 20130519
(experimental).

A variation of the program:

//-------------------------------------------------
#include <vector>
#include <iostream>

int main()
{
  std::vector<int> x{1, 2, 3};

  auto y = [x] () mutable {
    for (auto &i: x)
      i++;
    return x;
  };

  for (const auto &i : y()) {
    std::cout << i << std::endl;
  }

  std::cout << "(1)" << std::endl;

  for (const auto &i : y()) {
    std::cout << i << std::endl;
  }

  std::cout << "(2)" << std::endl;
}
//-------------------------------------------------

produces the output:

2
3
4
(1)
(2)

I *think* the following is going on here: The actual closure member x is
(incorrectly) considered as a local variable during RVO analysis, therefore the
first invocation invokes the move constructor on that member with the effect of
leaving an empty vector x within the closure.

The behavior looks incorrect to me: Neither 12.8 p31 b1 nor p32 can be applied
here, because x is neither a variable with automatic storage duration nor a
function parameter. It is correct the 5.1.2 p10 says 

"The identifier in a simple-capture is looked up using the usual rules for
unqualified name lookup (3.4.1); each such lookup shall find a variable with
automatic storage duration declared in the reaching scope of the local lambda
expression."

but this is an automatic variable *not* within the closure's function call
operator. And 5.1.2 p15

"For each entity captured by copy, an unnamed nonstatic data member is declared
in the closure type."

is clear that x is considered a data member within the closure and RVO shall
not be applied to it.
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From: "burnus at gcc dot gnu.org" <gcc-bugzilla@gcc.gnu.org>
To: gcc-bugs@gcc.gnu.org
Subject: [Bug fortran/57435] [4.8/4.9 Regression] Ice on invalid: check_for_ambiguous
Date: Tue, 28 May 2013 07:00:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW435

Tobias Burnus <burnus at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |ice-on-invalid-code
                 CC|                            |burnus at gcc dot gnu.org
   Target Milestone|---                         |4.8.1

--- Comment #5 from Tobias Burnus <burnus at gcc dot gnu.org> ---
(In reply to Dominique d'Humieres from comment #3)
> Likely due to revision 195065:

Looks like (see PR 47203 / http://gcc.gnu.org/r195065).

(In reply to Dominique d'Humieres from comment #4)
> The following patch restores the 4.7 behavior:

The patch looks good to me.

[Bug c++/57437] [4.7/4.8/4.9 Regression] C++11: mutable lambdas; gcc 4.7-4.8

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57437

Jonathan Wakely <redi at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2013-05-28
      Known to work|                            |4.6.3
            Summary|C++11: mutable lambdas; gcc |[4.7/4.8/4.9 Regression]
                   |4.7-4.8                     |C++11: mutable lambdas; gcc
                   |                            |4.7-4.8
     Ever confirmed|0                           |1

[Bug c++/57437] [4.7/4.8/4.9 Regression] C++11: mutable lambdas

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57437

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|NEW                         |ASSIGNED
                 CC|                            |jason at gcc dot gnu.org
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org

[Bug c++/57437] [4.7/4.8/4.9 Regression] C++11: mutable lambdas

[jason at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57437

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|ASSIGNED                    |RESOLVED
         Resolution|---                         |FIXED
   Target Milestone|---                         |4.7.4

--- Comment #2 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 4.7.4/4.8.2/4.9.