Linking against boost barfs with 'undefined reference to `boost::system::get_system_category()'

Question

I'm having trouble statically linking an app which uses the boost 1.35 libraries. I'm using a linux debian Lenny box, with G++ 4.3.2. Linking without -static works without a hitch.

Specifically,

g++ -Wall -Wextra  -pedantic -ggdb3 -O0  -static -l boost_thread-mt -lboost_system-mt -lboost_program_options-mt -lssl -lpthread -l crypto  main.o comandos.o utils.o tunnel.o opciones.o decode.o sysutils.o -o sapp  

main.o: In function `__static_initialization_and_destruction_0':
/usr/include/boost/system/error_code.hpp:204:undefined reference to `boost::system::get_system_category()'
/usr/include/boost/system/error_code.hpp:205: undefined reference to `boost::system::get_posix_category()'
/usr/include/boost/system/error_code.hpp:209: undefined reference to `boost::system::get_posix_category()'
/usr/include/boost/system/error_code.hpp:210: undefined reference to `boost::system::get_system_category()'

I'm linking against boost_system-mt, which is found on my box in /usr/lib. The same thing happens if I link against the non multithread-safe version of boost_system (-lboost_system)

sarraga@saggy:~/sapp/src$ ls -al /usr/lib/libboost_system*a
-rw-r--r-- 1 root root 23506 2008-05-23 05:32 /usr/lib/libboost_system.a
lrwxrwxrwx 1 root root    17 2010-08-26 19:10 /usr/lib/libboost_system-gcc42-1_35.a -> libboost_system.a
lrwxrwxrwx 1 root root    20 2010-08-26 19:10 /usr/lib/libboost_system-gcc42-mt-1_35.a -> libboost_system-mt.a
-rw-r--r-- 1 root root 23506 2008-05-23 05:32 /usr/lib/libboost_system-mt.a

And I find the unresolved symbols there

sarraga@saggy:~/sapp/src$ nm -C /usr/lib/libboost_system-mt.a | grep 'T.*get.*category'
00000050 T boost::system::get_posix_category()
000000b0 T boost::system::get_system_category()

An strace shows that the linker opens the library

 sarraga@saggy:~/sapp/src$ strace -f make 2>&1 | grep boost_system
[pid 15016] execve("/usr/bin/g++", ["g++", "-Wall", "-Wextra", "-pedantic", "-ggdb3", "-O0", "-static", "-l", "boost_thread-mt", "-lboost_system-mt", "-lboost_program_options-mt", "-lssl", "-lpthread", "-l", "crypto", "main.o", ...], [/* 41 vars */] <unfinished ...>
...
[pid 15018] open("/usr/lib/gcc/i486-linux-gnu/4.3.2/../../../../lib/libboost_system-mt.a", O_RDONLY|O_LARGEFILE) = 8

It's a standard package installation of boost in debian,

sarraga@saggy:~/sapp/src$ dpkg -l | grep boos
ii  libboost-date-time1.35-dev           1.35.0-5                   set of date-time libraries based on generic programming
ii  libboost-date-time1.35.0             1.35.0-5                   set of date-time libraries based on generic programming
ii  libboost-filesystem1.35-dev          1.35.0-5                   filesystem operations (portable paths, iteration over d
ii  libboost-filesystem1.35.0            1.35.0-5                   filesystem operations (portable paths, iteration over d
ii  libboost-graph1.35-dev               1.35.0-5                   generic graph components and algorithms in C++
ii  libboost-graph1.35.0                 1.35.0-5                   generic graph components and algorithms in C++
ii  libboost-iostreams1.35-dev           1.35.0-5                   Boost.Iostreams Library development files
ii  libboost-iostreams1.35.0             1.35.0-5                   Boost.Iostreams Library
ii  libboost-program-options1.35-dev     1.35.0-5                   program options library for C++
ii  libboost-program-options1.35.0       1.35.0-5                   program options library for C++
ii  libboost-python1.35-dev              1.35.0-5                   Boost.Python Library development files
ii  libboost-python1.35.0                1.35.0-5                   Boost.Python Library
ii  libboost-regex1.35-dev               1.35.0-5                   regular expression library for C++
ii  libboost-regex1.35.0                 1.35.0-5                   regular expression library for C++
ii  libboost-serialization1.35-dev       1.35.0-5                   serialization library for C++
ii  libboost-serialization1.35.0         1.35.0-5                   serialization library for C++
ii  libboost-signals1.35-dev             1.35.0-5                   managed signals and slots library for C++
ii  libboost-signals1.35.0               1.35.0-5                   managed signals and slots library for C++
ii  libboost-system1.35-dev              1.35.0-5                   Operating system (e.g. diagnostics support) library
ii  libboost-system1.35.0                1.35.0-5                   Operating system (e.g. diagnostics support) library
ii  libboost-test1.35-dev                1.35.0-5                   components for writing and executing test suites
ii  libboost-test1.35.0                  1.35.0-5                   components for writing and executing test suites
ii  libboost-thread1.35-dev              1.35.0-5                   portable C++ multi-threading
ii  libboost-thread1.35.0                1.35.0-5                   portable C++ multi-threading
ii  libboost-wave1.35-dev                1.35.0-5                   C99/C++ preprocessor library
ii  libboost-wave1.35.0                  1.35.0-5                   C99/C++ preprocessor library
ii  libboost1.35-dev                     1.35.0-5                   Boost C++ Libraries development files
ii  libboost1.35-doc                     1.35.0-5                   Boost.org libraries documentation

I'm sure I'm missing an stupid detail, but I can't find it. Anybody help?

Solution

When statically linking the linker expects that libraries will come after the files containing references to them. You need to move your .o files before your -l flags. The idea is that files that come later 'fill in' references contained in earlier files -- since your .o files are last, the linker expects them to fill in any missing symbols in boost_system rather than vice versa. When you dynamically link, the order doesn't matter because it doesn't resolve a symbol until the first time it's used at runtime (and by that time it knows the full list of libraries to look for symbols in).

Comments

[Santiago Árraga]

D'oh! <slaps forehead>. Works beautifully now.