why "undefined reference to `boost::system::generic_category" even if I do link against boost_system
boost, gcc, linker
Solution
The order at which you link your libraries matters, in your case you have `library.cpp` that apparently uses the `boost_system` library
library.cpp:(.text+0x25f): undefined reference to `boost::system::generic_category()'
library.cpp:(.text+0x269): undefined reference to `boost::system::generic_category()'
library.cpp:(.text+0x273): undefined reference to `boost::system::system_category()'
To solve this you should move the boost_system library to the end of your link line
g++ -o build/myproject build/main/main.o -L/usr/local/boost/boost_1_52_0/boost/libs -L/usr/lib -Lbuild -L. -lboost_thread -lpthread -lboost_regex -lpq -lmylibrary **-lboost_system**
Alternatively, build `libmylibrary.so` as a shared library and link to the `boost_system` library directly.
Problem
I would understand this error message if I had not put the `-lboost_system` flag, but it is really here: ``` g++ -o build/myproject build/main/main.o -L/usr/local/boost/boost_1_52_0/boost/libs -L/usr/lib -Lbuild -L. -lboost_system -lboost_thread -lpthread -lboost_regex -lpq -lmylibrary build/libmylibrary.a(library.o): In function `__static_initialization_and_destruction_0(int, int)': library.cpp:(.text+0x25f): undefined reference to `boost::system::generic_category()' library.cpp:(.text+0x269): undefined reference to `boost::system::generic_category()' library.cpp:(.text+0x273): undefined reference to `boost::system::system_category()' ``` Do you have any idea what should I investigate to solve the problem ? (I use gcc 4.6.3)