CMake: Linking statically against libgcc and libstdc++ into a shared library

23
votes

Problem:

I am having difficulties linking glibcc/glibc++ into a shared library using CMake and GCC4.9 on my Ubuntu 16.04 installation.

Additional conditions:

Loading the shared library gives a problem om the Red Hat production environment(where I copy it to), I believe because it uses a different libstc++ version(error: GLIBCXX_3_4_20 not found). I do not have sudo rights and cannot upgrade the machine.

As I derived from this blog, this post, I tried linking static linking against libgcc and libgc++ using:

set(CMAKE_EXE_LINKER_FLAGS "-static-libgcc -static-libstdc++ -static")

and againg using 

set(CMAKE_SHARED_LINKER_FLAGS "-static-libgcc -static-libstdc++ -static")

But that doesn't work. What does work is this CMake script: 

add_library(myLib SHARED ${SOURCE_FILES})
set(CMAKE_EXE_LINKER_FLAGS " -static")
target_link_libraries(myLib -static-libgcc -static-libstdc++)

This must be the wrong way of doing this, to my knowledge -static-libgcc and -static-libstdc++ are linker options and not libraries...

Question: How do I link statically against -libgcc and -libstdc++ correctly?

Thanks in advance!

2
c++gcccmakeg++static-linking

2 Answers

16
votes

Yes, target_link_libraries is a correct way to set linker flags or linker options.

Documentation of target_link_libraries:

Specify libraries or flags to use when linking a given target.

Item names starting with -, but not -l or -framework, are treated as linker flags.

https://cmake.org/cmake/help/v3.0/command/target_link_libraries.html (emphasis not in original)

3
votes

As of cmake 3.13, there is a new cmake function for general linker options:

https://cmake.org/cmake/help/v3.13/command/target_link_options.html

target_link_options(<target> [BEFORE]
  <INTERFACE|PUBLIC|PRIVATE> [items1...]
  [<INTERFACE|PUBLIC|PRIVATE> [items2...] ...])

The appropriate way to specify libraries to be linked is still:

https://cmake.org/cmake/help/v3.13/command/target_link_libraries.html

target_link_libraries(<target>
  <PRIVATE|PUBLIC|INTERFACE> <item>...
  [<PRIVATE|PUBLIC|INTERFACE> <item>...]...)

There are a few different signatures depending on whether or not you want these libraries to be propagated to dependent targets, so be sure to check the docs.