4

I am compiling a program against a shared library I have written. This library in turn relies on Boost::program_options (among other libraries). When I compile my program, I need of course to mention my library, but I get a DSO error:

g++ ism_create_conf.cc -o ism_create_conf -lglsim_ol -lglsim -lhdf5 -lgsl

/usr/bin/ld.real: /tmp/cc9mBWmM.o: undefined reference to symbol_ZN5boost15program_options8validateERNS_3anyERKSt6vectorISsSaISsEEPSsi'
//usr/lib/x86_64-linux-gnu/libboost_program_options.so.1.55.0: error adding symbols: DSO missing from command line
collect2: error: ld returned 1 exit status

I know that the error goes away if I add -lboost_program_options. What I don't understand is

  1. Why do I have to do this even if my program does not call Boost directly (only through my glsim library).

  2. Why does the linker want -lboost_program_options when it actually found the correct library (and location) by itself (see the second line of the error message).

The situation is similar to what was asked e.g here, but I am asking something different: I know the solution is to mention the library in the command line, I want to know why I have to do this even if the linker already knows where the library is. There is obviously something I do not understand about how shared libraries work, it seems to me that when I use other shared libraries, these libraries can automatically call other shared libraries they need. However, the shared library I built does not have this ability.

TomasG
  • 310
  • 2
  • 9
  • Possible duplicate of [Strange linking error: DSO missing from command line](https://stackoverflow.com/questions/19901934/strange-linking-error-dso-missing-from-command-line) – perror Jul 18 '17 at 16:45
  • @perror Thanks, but my question is not exactly the same, see edit. – TomasG Jul 19 '17 at 13:08
  • what if you add `-Wl,--allow-shlib-undefined` at the end of call of `g++`? – fghj Jul 19 '17 at 13:28

1 Answers1

2

Modern distros (e.g. Ubuntu Natty and later) enable --as-needed flag by default in their toolchains. One of side-effects is that linker tracks order of libraries more strictly (not sure why this was done, probly to match static libraries case).

yugr
  • 19,769
  • 3
  • 51
  • 96