[Bug c++/57207] New: Incorrect lifetime of const references bound to temporary

[DimanNe at ya dot ru]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=57207



             Bug #: 57207

           Summary: Incorrect lifetime of const references bound to

                    temporary

    Classification: Unclassified

           Product: gcc

           Version: 4.7.3

            Status: UNCONFIRMED

          Severity: normal

          Priority: P3

         Component: c++

        AssignedTo: unassig...@gcc.gnu.org

        ReportedBy: dima...@ya.ru





Created attachment 30053

  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=30053

main.ii generated via --save-temps



Here the programme:



#include <iostream>

struct TMyStruct

   { };

struct TByteArrayList

   {

      TByteArrayList(const TByteArrayList &)

         { i = 12; std::cout << "copy ctor " << this << std::endl; }

      TByteArrayList &operator=(const TByteArrayList &)

         { std::cout << "operator = " << this << std::endl; return *this; }

      TByteArrayList()

         { i = 12; std::cout << "ctor " << this << std::endl; }

      ~TByteArrayList()

         { std::cout << "dtor " << this << std::endl; }



      TByteArrayList &operator<<(const TMyStruct &)

         { std::cout << "<< " << this << std::endl; return *this; }



      int i;

   };



int main()

   {

      const TByteArrayList &List = TByteArrayList() << TMyStruct();



      std::cout << "Here some use of List: " << List.i << " address " << &List

<< std::endl;



      return 0;

   }





And here its output:



ctor 0x7fff22f27350

<< 0x7fff22f27350

dtor 0x7fff22f27350

Here some use of List: 12 address 0x7fff22f27350



Why dtor of List called right after List is created in this line

      const TByteArrayList &List = TByteArrayList() << TMyStruct();



Why const reference to temporary object (List) does not prolong life time of

temporary object (TByteArrayList() << TMyStruct())?



Seems it is a bug.





//===============================================



$ gcc -v

Using built-in specs.

COLLECT_GCC=gcc

COLLECT_LTO_WRAPPER=/usr/lib/gcc/x86_64-linux-gnu/4.7/lto-wrapper

Target: x86_64-linux-gnu

Configured with: ../src/configure -v --with-pkgversion='Ubuntu/Linaro

4.7.3-1ubuntu1' --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

--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

--with-system-zlib --enable-objc-gc --with-cloog --enable-cloog-backend=ppl

--disable-cloog-version-check --disable-ppl-version-check --enable-multiarch

--disable-werror --with-arch-32=i686 --with-abi=m64

--with-multilib-list=m32,m64,mx32 --with-tune=generic --enable-checking=release

--build=x86_64-linux-gnu --host=x86_64-linux-gnu --target=x86_64-linux-gnu

Thread model: posix

gcc version 4.7.3 (Ubuntu/Linaro 4.7.3-1ubuntu1)