[Bug c++/56636] New: strange interaction of dynamic_cast and unique_ptr

[Bug c++/56636] New: strange interaction of dynamic_cast and unique_ptr

[gcc-bugs at naturalcleaningcalgary dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

             Bug #: 56636
           Summary: strange interaction of dynamic_cast and unique_ptr
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: gcc-bugs@naturalcleaningcalgary.com


The following program produces a segfault at the dynamic_cast.  If I change
std::unique_ptr<int> to int*, or if I drop the dynamic_cast, the segfault goes
away.


#include <memory>

struct A
{
    void F() const
    {
        F_impl();
    }

    virtual std::unique_ptr<int> F_impl() const = 0;
};

template <typename Derived>
    struct A_impl : virtual A
{
    std::unique_ptr<int> F_impl() const override
    {
        dynamic_cast<const Derived &>(*this);
        return nullptr;
    }
};

struct B : virtual A {};

struct C : B, A_impl<C> {};

int main()
{
    C().F();
}


$ g++ -std=c++11 -otest test.cpp && ./test.exe

I am using GCC 4.7.2 under MinGW, configured with "--enable-libstdcxx-debug
--enable-languages=c,c++ --build=pentium4-pc-mingw32 --disable-nls
--disable-win32-registry --enable-threads".


(gdb) run
Starting program: c:\devel\page\build/test.exe
[New Thread 2356.0xa10]

Program received signal SIGSEGV, Segmentation fault.
__cxxabiv1::__dynamic_cast (src_ptr=0x4031f4, src_type=0x403180,
    dst_type=0x403160, src2dst=4)
    at ../../../../gcc-4.7.2/libstdc++-v3/libsupc++/dyncast.cc:56
56            adjust_pointer <void> (src_ptr, prefix->whole_object);
(gdb) bt
#0  __cxxabiv1::__dynamic_cast (src_ptr=0x4031f4, src_type=0x403180,
    dst_type=0x403160, src2dst=4)
    at ../../../../gcc-4.7.2/libstdc++-v3/libsupc++/dyncast.cc:56
#1  0x00401d04 in A_impl<C>::F_impl() const ()
#2  0x00401cc6 in A::F() const ()
#3  0x00401378 in main ()

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Target|                            |mingw

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> 2013-03-16 17:39:54 UTC ---
Must be a target issue, it works fine on x86_64-linux

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

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

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |daniel.kruegler at
                   |                            |googlemail dot com

--- Comment #2 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2013-03-20 08:38:22 UTC ---
It also works for gcc 4.8.0 trunk using mingw 64.
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Subject: [Bug middle-end/56657] [GCC 4.6/4.7] ICE - error: unrecognizable insn.
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http://gcc.gnu.org/bugzilla/show_bug.cgi?idV657

Mikael Pettersson <mikpe at it dot uu.se> changed:

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----------------------------------------------------------------------------
                 CC|                            |mikpe at it dot uu.se

--- Comment #4 from Mikael Pettersson <mikpe at it dot uu.se> 2013-03-20 08:43:05 UTC ---
The non-preprocessed test case doesn't ICE for me with gcc-4.7.2 targeting
x86_64-w64-mingw32 (so not the same "mingw" as the reporter is using), with
either -m64 or -m32.  The preprocessed test case does ICE that compiler with
-m32, but not with -m64.

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[paolo.carlini at oracle dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

--- Comment #3 from Paolo Carlini <paolo.carlini at oracle dot com> 2013-03-20 09:43:46 UTC ---
(friendly note to Daniel: "gcc 4.8.0 trunk" doesn't make much sense ;) Either
you mean trunk (future 4.9) or the recently created gcc-4_8-branch branch, from
which 4.8.0 will be released. Or maybe both, I don't know)

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[daniel.kruegler at googlemail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

--- Comment #4 from Daniel Krügler <daniel.kruegler at googlemail dot com> 2013-03-20 10:19:47 UTC ---
(In reply to comment #3)
I tested gcc 4.8.0 20130310 (experimental)
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--- Comment #4 from Rolf Ebert <rolf.ebert.gcc at gmx dot de> 2013-03-20 10:23:43 UTC ---
I used the release candidate 4.8.0 from 2013-03-16 (see initial problem
description)

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[paolo.carlini at oracle dot com]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

Paolo Carlini <paolo.carlini at oracle dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |ktietz at gcc dot gnu.org

--- Comment #5 from Paolo Carlini <paolo.carlini at oracle dot com> ---
Maybe Kai can double check that we can close this.

[Bug c++/56636] strange interaction of dynamic_cast and unique_ptr

[ktietz at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=56636

Kai Tietz <ktietz at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |WORKSFORME

--- Comment #6 from Kai Tietz <ktietz at gcc dot gnu.org> ---
So tested it for 4.8 (branch), 4.9 (branch), and 5.0 (trunk).

I can't reproduce this ICE, so I close this bug as fixed "worksforme".