[Bug c++/50028] New: Ternary operator and static const member variable

[Bug c++/50028] New: Ternary operator and static const member variable

[protocolocon at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

           Summary: Ternary operator and static const member variable
           Product: gcc
           Version: 4.6.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: protocolocon@gmail.com


Created attachment 24960
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24960
Preprocessor intermediate file

Problem:

The following code:

#include <stdlib.h>
#include <stdio.h>

class test
{
public:
    static const unsigned char OPT1=27;
    static const unsigned char OPT2=72;
};

int main()
{
    unsigned cond=rand();
    unsigned value1, value2;
    if(cond) value1=test::OPT1; else value1=test::OPT2;
    value2=cond?test::OPT1:test::OPT2;
    printf("%d %d\n", value1, value2);
    return 0;
}

Compiles w/o warnings with:

$ g++ -Wall -Wextra -o testO2 -g -O2 test.cc

But fails to compile/link with:

$ g++ -Wall -Wextra -o testO2 -g -O0 test.cc
/tmp/ccwLVGVv.o: In function `main':
/home/asier/desarrollo/tmp/gcc_poc/test.cc:16: undefined reference to
`test::OPT1'
/home/asier/desarrollo/tmp/gcc_poc/test.cc:16: undefined reference to
`test::OPT2'
collect2: ld returned 1 exit status


Analysis:

The problem only happens in the ternary operator, but not in the if statement
that precedes it. Compiler is not substituting class constants in conditional
operator so that compilation unit gets a reference to a test::OPT1 and
test::OPT2 in the .rodata section (that actually does not exist).


See attacked preprocesor output and intermediate assembly code.







Compilers tested:

GCC 4.3

Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.3.5-4'
--with-bugurl=file:///usr/share/doc/gcc-4.3/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr --enable-shared
--enable-multiarch --enable-linker-build-id --with-system-zlib
--libexecdir=/usr/lib --without-included-gettext --enable-threads=posix
--enable-nls --with-gxx-include-dir=/usr/include/c++/4.3 --program-suffix=-4.3
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc --enable-mpfr
--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 4.3.5 (Debian 4.3.5-4) 

GCC 4.4

Using built-in specs.
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.4.5-8'
--with-bugurl=file:///usr/share/doc/gcc-4.4/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++ --prefix=/usr
--program-suffix=-4.4 --enable-shared --enable-multiarch
--enable-linker-build-id --with-system-zlib --libexecdir=/usr/lib
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.4 --libdir=/usr/lib --enable-nls
--enable-clocale=gnu --enable-libstdcxx-debug --enable-objc-gc
--with-arch-32=i586 --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 4.4.5 (Debian 4.4.5-8) 

GCC 4.6

Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/usr/lib/x86_64-linux-gnu/gcc/x86_64-linux-gnu/4.6.1/lto-wrapper
Target: x86_64-linux-gnu
Configured with: ../src/configure -v --with-pkgversion='Debian 4.6.1-4'
--with-bugurl=file:///usr/share/doc/gcc-4.6/README.Bugs
--enable-languages=c,c++,fortran,objc,obj-c++,go --prefix=/usr
--program-suffix=-4.6 --enable-shared --enable-multiarch
--with-multiarch-defaults=x86_64-linux-gnu --enable-linker-build-id
--with-system-zlib --libexecdir=/usr/lib/x86_64-linux-gnu
--without-included-gettext --enable-threads=posix
--with-gxx-include-dir=/usr/include/c++/4.6 --libdir=/usr/lib/x86_64-linux-gnu
--enable-nls --enable-clocale=gnu --enable-libstdcxx-debug
--enable-libstdcxx-time=yes --enable-plugin --enable-objc-gc
--with-arch-32=i586 --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 4.6.1 (Debian 4.6.1-4) 


System info:
Linux frito 2.6.32-5-amd64 #1 SMP Mon Mar 7 21:35:22 UTC 2011 x86_64 GNU/Linux

[Bug c++/50028] Ternary operator and static const member variable

[protocolocon at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

--- Comment #1 from protocolocon <protocolocon at gmail dot com> 2011-08-09 13:55:05 UTC ---
Created attachment 24961
  --> http://gcc.gnu.org/bugzilla/attachment.cgi?id=24961
Intermediate assembly code

[Bug c++/50028] Ternary operator and static const member variable

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

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

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

--- Comment #2 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-08-09 14:08:25 UTC ---
you need to define the static members

PR 10483
PR 13795
PR 13332
PR 44673
etc. etc. etc

[Bug c++/50028] Ternary operator and static const member variable

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-08-09 14:16:03 UTC ---
and PR 42101

and finally,
http://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition

[Bug c++/50028] Ternary operator and static const member variable

[protocolocon at gmail dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

--- Comment #4 from protocolocon <protocolocon at gmail dot com> 2011-08-09 14:32:04 UTC ---
(In reply to comment #3)
> and PR 42101
> 
> and finally,
> http://gcc.gnu.org/wiki/VerboseDiagnostics#missing_static_const_definition

Thanks for the fast replay and sorry for submitting a duplicate.
Still not completely convinced, but I will assimilate it.

[Bug c++/50028] Ternary operator and static const member variable

[redi at gcc dot gnu.org]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=50028

--- Comment #5 from Jonathan Wakely <redi at gcc dot gnu.org> 2011-08-09 14:39:44 UTC ---
that last link should be
http://gcc.gnu.org/wiki/VerboseDiagnostics#undefined_reference_to_.60S::a.27
(I'm not sure why the "Permalink" doesn't work)