[Bug c++/57846] New: CRTP, templates, metaprogramming, forwarding and static member

[Bug c++/57846] New: CRTP, templates, metaprogramming, forwarding and static member

[vince.rev at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

            Bug ID: 57846
           Summary: CRTP, templates, metaprogramming, forwarding and
                    static member
           Product: gcc
           Version: 4.8.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: vince.rev at gmail dot com

This code (I could not find a simpler example) does not compile under g++ for
some obscure reasons (tested with 4.8.1 and 4.7.2) (see the related discussion
on stack overflow here :
http://stackoverflow.com/questions/17515079/crtp-templates-metaprogramming-forwarding-and-static-member-a-bug-in-g-4-8):

-------------------------------------------------------------
#include <iostream>
#include <type_traits>
#include <utility>
#include <tuple>
#include <array>

template <class Crtp, class... Types> struct Base
{
    template <unsigned int Index, class Type = typename
std::tuple_element<Index, std::tuple<Types...> >::type> inline const Type&
get() const {return std::get<Index>(data);}
    template <unsigned int Index, class Type = typename
std::tuple_element<Index, std::tuple<Types...> >::type> inline Crtp& set(const
Type& value) {std::get<Index>(data) = value; return static_cast<Crtp&>(*this);}
    std::tuple<Types...> data;
};

template <typename Type, unsigned int Size> struct Derived : public
Base<Derived<Type, Size>, std::array<Type, Size>>
{
    template <class... Args, class Template = decltype(std::declval<const
Base<Derived<Type, Size>, std::array<Type, Size>>>().template
get<0>(std::declval<Args>()...))> inline Template test(Args&&... args) const
{return this->template get<0>(std::forward<Args>(args)...);} 
    template <class... Args, class Template = decltype(std::declval<const
Base<Derived<Type, Size>, std::array<Type, Size>>>().template
set<0>(std::declval<Args>()...))> inline Derived<Type, Size>& test(Args&&...
args) {return this->template set<0>(std::forward<Args>(args)...);} 
    static void check() {Derived<double, 3> derived;
std::cout<<derived.test()[0]<<std::endl;}
};

int main(int argc, char* argv[])
{
    Derived<double, 3> derived; std::cout<<derived.test()[0]<<std::endl; //
Working
    Derived<double, 3>::check(); // Not working: error: no match for
‘operator[]’ (operand types are ‘Derived<double, 3u>’ and ‘int’)
    return 0;
}

-------------------------------------------------------------
>From gcc-bugs-return-425895-listarch-gcc-bugs=gcc.gnu.org@gcc.gnu.org Mon Jul 08 03:22:59 2013
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To: gcc-bugs@gcc.gnu.org
Subject: [Bug c/57847] New: Compile ARM linux kernel with configuration of SLUB allocator, kernel failed to boot
Date: Mon, 08 Jul 2013 03:22:00 -0000
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idW847

            Bug ID: 57847
           Summary: Compile ARM linux kernel with configuration of SLUB
                    allocator, kernel failed to boot
           Product: gcc
           Version: 4.7.3
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
          Assignee: unassigned at gcc dot gnu.org
          Reporter: lxz at knd dot com.cn

Tested kernel version is 3.2.21 and 3.2. Kernel encounters "data abort" during
initiation.
Problem exists in gcc 4.7.3 and 4.8.1, but 4.6.3 works fine.
Changing kernel configuration to SLAB allocator is a workaround.

[Bug c++/57846] CRTP, templates, metaprogramming, forwarding and static member

[vince.rev at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

--- Comment #1 from Vincent <vince.rev at gmail dot com> ---
Apparently, this is also a bug in the last version (4.9):
http://stackoverflow.com/questions/17515079/crtp-templates-metaprogramming-forwarding-and-static-member-a-bug-in-g-4-8

[Bug c++/57846] CRTP, templates, metaprogramming, forwarding and static member

[ville.voutilainen at gmail dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

Ville Voutilainen <ville.voutilainen at gmail dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Keywords|                            |rejects-valid
             Status|UNCONFIRMED                 |NEW
   Last reconfirmed|                            |2014-12-12
                 CC|                            |ville.voutilainen at gmail dot com
     Ever confirmed|0                           |1
      Known to fail|                            |4.8.2, 4.9.1, 5.0

--- Comment #2 from Ville Voutilainen <ville.voutilainen at gmail dot com> ---
We badly need a reduced testcase for this.

[Bug c++/57846] CRTP, templates, metaprogramming, forwarding and static member

[harald at gigawatt dot nl]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

Harald van Dijk <harald at gigawatt dot nl> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |harald at gigawatt dot nl

--- Comment #3 from Harald van Dijk <harald at gigawatt dot nl> ---
Somewhat reduced:

template <typename T>
struct A
{
  template <typename T2>
  void f();
};

template <typename T>
struct B
{
  int &f() const;

  template <typename T2 = T, typename = decltype(A<T2>().template f<T2>(T2()))>
  void f();

  void g() {
    int *i = &B<int>().f();
  }
};

Accepted by clang 3.4.2, rejected by gcc 4.8.3 and 4.9.0 with:

test.cc: In member function ‘void B<T>::g()’:
test.cc:17:26: error: lvalue required as unary ‘&’ operand

It seems to only happen when certain operators are used: there is no error when
doing e.g.

  int &i = B<int>().f();
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Subject: [Bug ipa/64298] New: [5 Regression] ICE: Segmentation fault in get_binfo_at_offset at tree.c:11914
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https://gcc.gnu.org/bugzilla/show_bug.cgi?idd298

            Bug ID: 64298
           Summary: [5 Regression] ICE: Segmentation fault in
                    get_binfo_at_offset at tree.c:11914
           Product: gcc
           Version: 5.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: ipa
          Assignee: unassigned at gcc dot gnu.org
          Reporter: danglin at gcc dot gnu.org
              Host: hppa-unknown-linux-gnu
            Target: hppa-unknown-linux-gnu
             Build: hppa-unknown-linux-gnu

In r218651, the following ICE occurs:

spawn /home/dave/gnu/gcc/objdir/gcc/testsuite/g++/../../xg++
-B/home/dave/gnu/gc
c/objdir/gcc/testsuite/g++/../../
/home/dave/gnu/gcc/gcc/gcc/testsuite/g++.dg/ip
a/pr64059.C -fno-diagnostics-show-caret -fdiagnostics-color=never -nostdinc++
-I/home/dave/gnu/gcc/objdir/hppa-linux-gnu/libstdc++-v3/include/hppa-linux-gnu
-I/
home/dave/gnu/gcc/objdir/hppa-linux-gnu/libstdc++-v3/include
-I/home/dave/gnu/gc
c/gcc/libstdc++-v3/libsupc++
-I/home/dave/gnu/gcc/gcc/libstdc++-v3/include/backw
ard -I/home/dave/gnu/gcc/gcc/libstdc++-v3/testsuite/util -fmessage-length=0
-std
=gnu++98 -r -nostdlib -O2 -flto -fno-devirtualize -S -o pr64059.s
/home/dave/gnu/gcc/gcc/gcc/testsuite/g++.dg/ipa/pr64059.C:56:1: internal
compiler error: Segmentation fault
0x685e57 crash_signal
        ../../gcc/gcc/toplev.c:358
0x894508 get_binfo_at_offset(tree_node*, long long, tree_node*)
        ../../gcc/gcc/tree.c:11914
0x4d044f possible_polymorphic_call_targets(tree_node*, long long,
ipa_polymorphi
c_call_context, bool*, void**, bool)
        ../../gcc/gcc/ipa-devirt.c:2404
0x5661db possible_polymorphic_call_targets(cgraph_edge*, bool*, void**, bool)
        ../../gcc/gcc/ipa-utils.h:109
0x5661db compute_ltrans_boundary(lto_symtab_encoder_d*)
        ../../gcc/gcc/lto-cgraph.c:952
0x5bfabb ipa_write_summaries(bool)
        ../../gcc/gcc/passes.c:2511
0x327e53 ipa_passes
        ../../gcc/gcc/cgraphunit.c:2093
0x327e53 symbol_table::compile()
        ../../gcc/gcc/cgraphunit.c:2189
0x32936b symbol_table::finalize_compilation_unit()
        ../../gcc/gcc/cgraphunit.c:2338
0x191527 cp_write_global_declarations()
        ../../gcc/gcc/cp/decl2.c:4688
Please submit a full bug report,

[Bug c++/57846] CRTP, templates, metaprogramming, forwarding and static member

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|NEW                         |RESOLVED
           See Also|                            |https://gcc.gnu.org/bugzill
                   |                            |a/show_bug.cgi?id=83160

--- Comment #4 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
Fixed in GCC 8, most likely by the patch which fixed PR 83160.

[Bug c++/57846] CRTP, templates, metaprogramming, forwarding and static member

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=57846

Andrew Pinski <pinskia at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |8.3