[Bug c++/55988] New: Incorrect code generation with const and -std=c++0x

["pavel.zbitskiy at gmail dot com" <gcc-bugzilla at gcc dot gnu dot org>]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=55988

             Bug #: 55988
           Summary: Incorrect code generation with const and -std=c++0x
    Classification: Unclassified
           Product: gcc
           Version: 4.7.2
            Status: UNCONFIRMED
          Severity: major
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: pavel.zbitskiy@gmail.com


Created attachment 29167
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=29167
the preprocessed file

The following code
/* ---------- */
class Base
{
public:
    virtual void execute() const = 0;
    virtual ~Base() {}
};

class Pop : public Base
{
public:
    virtual void execute() const { return; }
};

const Pop pop;

int main()
{
    pop.execute();
    return 0;
}
/* ---------- */

will be crashed if source is compiled with -std=c++0x (g++ -Wall -Wextra
-std=c++0x const-0x.cpp -o const-0x).

This happens because variable pop is located in read-only memory
080487f8 l     O .rodata        00000004              _ZL3pop

and Pop::~Pop() has the following code
   0x080486ba <+6>:    mov    eax,DWORD PTR [ebp+0x8]
=> 0x080486bd <+9>:    mov    DWORD PTR [eax],0x80487b0
   0x080486c3 <+15>:    mov    eax,DWORD PTR [ebp+0x8]
(gdb) info registers eax
eax            0x80487f8

In other words it tries to write to read-only location.

For more complicated programs the following code was generated in destructor:
   0xb7b66b34 <+20>: mov eax,DWORD PTR [esp+0x4]
=> 0xb7b66b38 <+24>: mov DWORD PTR [eax],edx
   0xb7b66b3a <+26>: ret
with the same consequences.

System information:
Linux laptop-1 3.5.0-21-generic #32-Ubuntu SMP Tue Dec 11 18:52:46 UTC 2012
i686 i686 i686 GNU/Linux

g++ -v output:
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=/usr/lib/gcc/i686-linux-gnu/4.7/lto-wrapper
Target: i686-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro
4.7.2-2ubuntu1' --with-bugurl=file:///usr/share/doc/gcc-4.7/README.Bugs
--enable-languages=c,c++,go,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.7 --enable-shared --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib --without-included-gettext
--enable-threads=posix --with-gxx-include-dir=/usr/include/c++/4.7
--libdir=/usr/lib --enable-nls --with-sysroot=/ --enable-clocale=gnu
--enable-libstdcxx-debug --enable-libstdcxx-time=yes --enable-gnu-unique-object
--enable-plugin --enable-objc-gc --enable-targets=all --disable-werror
--with-arch-32=i686 --with-tune=generic --enable-checking=release
--build=i686-linux-gnu --host=i686-linux-gnu --target=i686-linux-gnu
Thread model: posix
gcc version 4.7.2 (Ubuntu/Linaro 4.7.2-2ubuntu1)