How to find my generated shared library from cmake? - c++

Question

I want to create a shared library from cmake . I have a simple test.cpp .
My CMakeLists.txt looks like below
cmake_minimum_required(VERSION 2.8)
project (test)
set(CMAKE_BUILD_TYPE Release)
#include_directories(${CMAKE_CURRENT_SOURCE_DIR}/include)
add_library(test SHARED /home/tuhin/test/test1/test.cpp)
But I am not able to find "test" which my .so, I have seen test.dir folder created but not .so
Please help me to understand the issue.

Answer 1

(I suppose you read the comments and acted accordingly...)
(I also suppose you need a way to find out where your library will be placed, from within CMake build system)
The disk location of any target does not depend on CMakeLists.txt only, but also on the choice of the generator. Multi config generators like Visual Studio something, or Xcode might append configuration name as an additional directory, so you may get different results just by choosing a different generator.
This means that there is no easy way to uniquely identify disk location during configure stage. On the other hand, you may very easily check that information during the build stage:
cmake_minimum_required(VERSION 3.15)
project (lib_file_name)
add_library(my_test_lib SHARED my_test_lib.cpp)
add_custom_target(output_lib_name
ALL
COMMAND ${CMAKE_COMMAND} -E echo "my_test_lib location: $<TARGET_FILE:my_test_lib>"
)
note add_custom_target line:
new target was added, named output_lib_name
it will be executed as a part of building the default target (-> ALL)
command to build this target is asking cmake to output the file name of the target in question, using CMAke generator expressions (--> COMMAND ${CMAKE_COMMAND} -E echo "my_test_lib location: $<TARGET_FILE:my_test_lib>")
If you run it with makefile generator:
$ cmake -S /tmp -B /tmp/make-build -G "Unix Makefiles" ; cmake --build /tmp/make-build
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/make-build
Scanning dependencies of target my_test_lib
[ 50%] Building CXX object CMakeFiles/my_test_lib.dir/my_test_lib.cpp.o
[100%] Linking CXX shared library libmy_test_lib.dylib
[100%] Built target my_test_lib
Scanning dependencies of target output_lib_name
my_test_lib location: /tmp/make-build/libmy_test_lib.dylib
[100%] Built target output_lib_name
Note the line
my_test_lib location: /tmp/make-build/libmy_test_lib.dylib
if you run it with Xcode generator:
configure:
$ cmake -S /tmp -B /tmp/xcode-build -G Xcode
-- Configuring done
-- Generating done
-- Build files have been written to: /tmp/xcode-build
build release configuration:
$ cmake --build /tmp/xcode-build --config Release
........... lot of output deleted ...........
my_test_lib location: /tmp/xcode-build/Release/libmy_test_lib.dylib
** BUILD SUCCEEDED **
build debug configuration:
$ cmake --build /tmp/xcode-build --config Debug
........... lot of output deleted ...........
my_test_lib location: /tmp/xcode-build/Debug/libmy_test_lib.dylib
** BUILD SUCCEEDED **
Note how the location is different for different configuration builds, without any change in CMake build system.
At the end, this is the cmake documentation about add_custom_command, cmake generator expressions.