Linking with dynamic library with dependencies

by

It looks like you are most of the way there already. Well done with your investigation. Let’s see if I can help clear up the ‘why’ behind it.

Here’s what the linker is doing. When you link your executable (‘main’ above) it has some symbols (functions and other things) that are unresolved. It will look down the list of libraries that follow, trying to resolve unresolved symbols. Along the way, it finds that some of the symbols are provided by libB.so, so it notes that they are now resolved by this library.

However, it also discovers that some of those symbols use other symbols that are not yet resolved in your executable, so it now needs to resolve those as well. Without linking against libA.so, your application would be incomplete. Once it links against libA.so, all symbols are resolved and linking is complete.

As you saw, the use of -unresolved-symbols-in-shared-libs, doesn’t fix the problem. It just defers it so that those symbols are resolved at run time. That’s what -rpath is for: to specify the libraries to be searched at run time. If those symbols can’t be resolved then, your app will fail to start.

It’s not an easy thing to figure out library dependencies because a symbol could be provided by more than one library and be satisfied by linking against any one of them.

There is another description of this process here: Why does the order in which libraries are linked sometimes cause errors in GCC?

More Related Contents:

  1. GCC dump preprocessor defines
  2. LD_LIBRARY_PATH vs LIBRARY_PATH
  3. How to see which flags -march=native will activate?
  4. How can I have a Makefile automatically rebuild source files that include a modified header file? (In C/C++)
  5. How do I check if gcc is performing tail-recursion optimization?
  6. OS X 10.9 gcc links to clang
  7. What’s the difference between gcc and g++/gcc-c++?
  8. Can CMake use g++ to compile C files?
  9. gcc/g++ option to place all object files into separate directory
  10. How do I set up CLion to compile and run?
  11. Why gcc 4.1 + gcov reports 100% branch coverage and newer (4.4, 4.6, 4.8) reports 50% for “p = new class;” line?
  12. Makefile removes object files for no reason
  13. How do I determine the dependencies of a .NET application?
  14. How to install GCC piece by piece with GMP, MPFR, MPC, ELF, without shared libraries?
  15. How can I tell, with something like objdump, if an object file has been built with -fPIC?
  16. How do I run the GCC preprocessor to get the code after macros like #define are expanded?
  17. make -j 8 g++: internal compiler error: Killed (program cc1plus)
  18. Cuda Clang and OS X Mavericks
  19. How is -march different from -mtune?
  20. How can I see parse tree, intermediate code, optimization code and assembly code during COMPILATION?
  21. How to set a variable in GCC with Intel syntax inline assembly?
  22. long double (GCC specific) and __float128
  23. Difference between regex_match and regex_search?
  24. Errors that refer to a bunch of unresolved OpenSSL symbols that clearly exist?
  25. Why does sqrt() work fine on an int variable if it is not defined for an int?
  26. make: *** [ ] Error 1 error [duplicate]
  27. -static option for gcc?
  28. How to specify an individual register as constraint in ARM GCC inline assembly?
  29. what is the order of source operands in AT&T syntax compared to Intel syntax?
  30. Compile with older libc (version `GLIBC_2.14′ not found)

Leave a Comment