Shared Libraries (Preview)

Source

06-shared-libraries-preview/
├── CMakeLists.txt
├── hello.c
├── hello-first.c
├── hello.h
├── hello-name.c
├── hello-name.h
└── hello-second.c

• 06-shared-libraries-preview/CMakeLists.txt

• 06-shared-libraries-preview/hello-first.c

• 06-shared-libraries-preview/hello-second.c

• 06-shared-libraries-preview/hello.h

• 06-shared-libraries-preview/hello.c

• 06-shared-libraries-preview/hello-name.c

• 06-shared-libraries-preview/hello-name.h

“Normal” Libraries

See also

• Targets, Properties, And More

• Shared Libraries (Shared Objects)

Documentation

• ADD_LIBRARY()

• STATIC

  • Simple bag of objects

  • Linker copies objects out

• SHARED

  • Loaded at runtime

  • ⟶ Loader (usually /lib64/ld-linux-x86-64.so.2)

  • More: Shared Libraries (Shared Objects)

• MODULE

  • No SONAME, no version symlinks

Building Shared Libraries

• In the CMakeLists.txt, using SHARED tag

  ADD_LIBRARY(hello SHARED hello.c hello-name.c)
  

• From the commandline, setting BUILD_SHARED_LIBS to ON

  $ cmake -DBUILD_SHARED_LIBS=ON ...
  

More About Loading

• Program interpreter ⟶ hash bang in scripts

• /etc/ld.so.conf

• Library SONAME and NEEDED tags ⟶ look in /usr/lib64/

  $ rpm -qf /usr/lib64/libboost_regex.so.1.76.0
  $ sudo dnf install boost-devel
  

• A-ha: development versions

  $ ls -l /usr/lib64/libboost_regex*
  lrwxrwxrwx. 1 root root     24 Jul 14  2022 /usr/lib64/libboost_regex.so -> libboost_regex.so.1.76.0
  -rwxr-xr-x. 1 root root 289264 Jul 14  2022 /usr/lib64/libboost_regex.so.1.76.0
  

• Temporarily add

  SET_PROPERTY(TARGET hello PROPERTY VERSION "1")``
  

  and modify to

  PROJECT(Demo VERSION "1.0.0")
  SET_PROPERTY(TARGET hello PROPERTY VERSION ${PROJECT_VERSION})
  

• Discuss ABI versions ⟶ rarely project versions can be used as ABI versions

• ⟶ can of worms: installation/deployment