Douglas Gregor wrote:
I'm having trouble getting programs using boost_unit_test_framework to link. The fundamental issue is that trying to link something like this:
g++ -fPIC -o algorithms_test algorithms_test.o - lboost_unit_test_framework
dies with a linker error:
/usr/bin/ld: Undefined symbols: _main collect2: ld returned 1 exit status
The issue, of course, is that "main" lives within the library boost_unit_test_framework, but linkers don't look into libraries (either static or dynamic) to find main.
I think this is false, see below.
Our tests pass because BBv2 decides to put the archive file on the link line:
g++ -fPIC -o algorithms_test algorithms_test.o libboost_unit_test_framework.a
For some reason, this non-standard practice seems to work... but I can't imagine it's truly portable,
It's absolutely portable.
and it forces users of boost_unit_test_framework into statically linking in a non- traditional way.
The above statements all seem to be false. There's no difference, in my testing, between libfoo.a and -L . -lfoo provided the latter finds the same libfoo.a. Further, in my testing putting 'main' in static library works. I believe that even works on Windows. Furthermore, previous testing reveals that on Linux, putting 'main' in shared library works as well. You can easily test it for yourself.
Why must main() be in a library? It seems a trivial matter to fix.
The real issue is that there's no 'main()' in library, as shown below: ghost@wind:~/Work/Boost/boost-rc/stage/lib$ readelf --symbols libboost_unit_test_framework-gcc40-d.so | grep main 871: 00074a43 17 OBJECT WEAK DEFAULT 12 _ZTSSt12domain_error 1253: 0007ed68 12 OBJECT WEAK DEFAULT 22 _ZTISt12domain_error 165: 00000000 0 FILE LOCAL DEFAULT ABS unit_test_main.cpp 259: 0007ed98 4 OBJECT LOCAL HIDDEN 22 DW.ref._ZTISt12domain_err 1128: 00074a43 17 OBJECT WEAK DEFAULT 12 _ZTSSt12domain_error 1510: 0007ed68 12 OBJECT WEAK DEFAULT 22 _ZTISt12domain_error When both static and shared libraries are present, gcc picks shared on most platforms of note. Since shared library lacks 'main', you get linker error. I believe this is intentional change made in Boost.Test for 1.34, in the interest of making Linux (where 'main' can be in shared library) and Windows (where 'main' cannot be in shared library), uniform. However, you'd need to ask Gennadiy how to your tests work now. - Volodya