I am trying to enable link time optimization in g++. My program compiles fine without the -flto option. When I add it to my Makefile the object files compile without errors, e.g.
g++ main.cpp -I ../includes -std=c++0x -fopenmp -Wall -pedantic -Wno-vla -flto -D INFO_ -c -o .obj/main.o
But when it comes to link the program:
g++ -fwhole-program -I ../includes -std=c++0x -fopenmp -Wall -pedantic -Wno-vla -flto -D INFO_ .obj/main.o .obj/atom.o .obj/bee.o .obj/colony.o ../includes/.obj/error.o ../includes/.obj/CmdLine.o ../includes/boost_lib_deb/libboost_program_options.a ../includes/gmp_lib_deb/lib/libgmpxx.a ../includes/gmp_lib_deb/lib/libgmp.a -o BeeBench
I get a lot of errors like these:
includes/gmp_lib_deb/lib/libgmpxx.a ../includes/gmp_lib_deb/lib/libgmp.a -o BeeBench
`typeinfo for boost::program_options::too_many_positional_options_error' referenced in section `.rodata._ZTVN5boost15program_options33too_many_positional_options_errorE[vtable for boost::program_options::too_many_positional_options_error]' of ../includes/boost_lib_deb/libboost_program_options.a(cmdline.o): defined in discarded section `.gnu.linkonce.t._ZTIN5boost15program_options33too_many_positional_options_errorE' of .obj/main.o (symbol from plugin)
`typeinfo for boost::program_options::too_many_positional_options_error' referenced in section `.rodata._ZTIN5boost16exception_detail19error_info_injectorINS_15program_options33too_many_positional_options_errorEEE[typeinfo for boost::exception_detail::error_info_injector<boost::program_options::too_many_positional_options_error>]' of ../includes/boost_lib_deb/libboost_program_options.a(cmdline.o): defined in discarded section `.gnu.linkonce.t._ZTIN5boost15program_options33too_many_positional_options_errorE' of .obj/main.o (symbol from plugin)
`typeinfo for boost::program_options::invalid_command_line_style' referenced in section `.rodata._ZTVN5boost15program_options26invalid_command_line_styleE[vtable for boost::program_options::invalid_command_line_style]' of ../includes/boost_lib_deb/libboost_program_options.a(cmdline.o): defined in discarded section `.gnu.linkonce.t._ZTIN5boost15program_options26invalid_command_line_styleE' of .obj/main.o (symbol from plugin)
I can't figure out what is going wrong. I compile all my object files using -flto. The libs, namely Boost and GMP, are compiled without -flto option. Is this causing the error? The gcc manual says that its ok to mix object files compiled with & without -flto option. Or am I missing something else, for example what is this plugin the error is speaking about?
I am using G++ 4.6.3 on Debian Wheezy.
UPDATE:
As adviced in the comments I made a minimal example. The code of my test program is only this:
#include "boost/program_options.hpp"
int main ( int argC, char* argV[] )
{
return 0;
}
When I compile it using:
g++ -o test -I ../includes -Wall -std=c++0x test.cpp -flto -fwhole-program -static
it gives similar errors as described above. If I omit the -static, -flto OR std=c++0x option it compiles without errors. The -fwhole-program option does not change the result. I now also tested with G++ 4.7, same error.
Any suggestions? Is this really a compiler error, or am I still doing something wrong?
Since I found no evidence, that there is something wrong with my code, I have posted a Boost bugreport. It was reproduced by other boost users as well, therefore I think it is actually a bug within boost or the g++. By now there was no response from the Boost maintainer. I'll update this post when there is one.
Update
It seems like the g++ linker-plugin is causing the problem (Still I have no idea why). Therefore a possible work around is to disable the linker-plugin by using -fno-use-linker-plugin.