shared_lib_cpp

How to create a shared library in C++

Compile with cmake

1. Create build dir

   $ mkdir build
   $ cd build
   

2. Generate makefiles

   $ cmake ..

3. Build library

   $ cmake --build ./ --target shared_lib_cpp -- -j4

Compile from console

1. To generate files in ./bin

   $ mkdir bin

2. All in one step

   $ g++ -fPIC -I ./include ./src/Foo.cpp ./src/library.cpp -shared -o ./bin/libshared_lib_cpp.so

3. Foo only in two-steps.

   • Build object

   $ g++ -c -fPIC ./src/Foo.cpp -I ./include -o ./bin/Foo.o

   • Build lib

   $ g++ -shared ./bin/Foo_shared.o -o ./bin/libFoo_shared.so

4. Check symbols

   $ nm -D ./bin/libshared_lib_cpp.so

5. Use in some binary from ./bin

   $ g++ main.cpp -L . -lFoo_shared -I ../include -o main_shared.out
   $ export LD_LIBRARY_PATH=.:$LD_LIBRARY_PATH
   $ ./main_shared.out
   

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Compile to static with cmake

add_library(${PROJECT_NAME} STATIC ${SOURCES})

Compile to static from console

1. Create object file:

   $ g++ -c ./src/Foo.cpp -I ./include -o ./bin/Foo_static.o

2. Create archive (static library)

   $ ar rvs ./bin/Foo_static.a ./bin/Foo_static.o

3. Check symbols

   $ nm ./bin/Foo_static.a

4. Use in some binary from ./bin

   $ g++ main.cpp Foo_static.a -I ../include -o main_static.out
   $ ./main_static.out
   

5. Show dynamically linked libraries

   $ ldd main.out

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See shared-libraries-linux-gcc