CMake target_link_libraries Interface Dependencies
CMake的链接选项：PRIVATE，INTERFACE，PUBLIC

测试PUBLIC

// foo.h
int foo();

struct A {
	int num1;
	double num2;
};

// foo.cpp
#include "foo.h"

int foo()
{
	return sizeof(A);
}

// bar.h
#include "foo.h"
int bar();

// bar.cpp
#include "bar.h"

int bar()
{
	return foo() * 10;
}

// main.cpp
#include <iostream>
#include "bar.h"

int main()
{
	std::cout << foo() << std::endl;
	std::cout << bar() << std::endl;
	return 0;
}

// CMakeLists.txt
cmake_minimum_required(VERSION 3.16)

project(foobar)
set(CMAKE_SKIP_RPATH TRUE)

include_directories(${CMAKE_SOURCE_DIR})

add_library(foo SHARED foo.cpp)

add_library(bar SHARED bar.cpp)
target_link_libraries(bar PUBLIC foo)

add_executable(main main.cpp)
target_link_libraries(main bar)

$ ldd *.so
libbar.so:
	linux-vdso.so.1 (0x00007ffddc3ed000)
	libfoo.so => /usr1/tmp/cmake1/build/libfoo.so (0x00007f8657389000)
libfoo.so:
	statically linked

$ nm -C main | grep "foo\|bar"
                 U bar()
                 U foo()

测试PRIVATE

// foo.h
struct A {
	int num1;
	double num2;
};

int foo();

// foo.cpp
#include "foo.h"

int foo()
{
	return sizeof(A);
}

// bar.h
int bar();

// bar.cpp
#include "foo.h"

int bar()
{
	return foo() * 10;
}

// main.cpp
#include <iostream>
#include "bar.h"

int main()
{
	std::cout << bar() << std::endl;
	return 0;
}

// CMakeLists.txt
cmake_minimum_required(VERSION 3.16)

project(foobar)
set(CMAKE_SKIP_RPATH TRUE)

include_directories(${CMAKE_SOURCE_DIR})

add_library(foo SHARED foo.cpp)

add_library(bar SHARED bar.cpp)
target_link_libraries(bar PRIVATE foo)

add_executable(main main.cpp)
target_link_libraries(main bar)

$ ldd *.so
libbar.so:
	linux-vdso.so.1 (0x00007ffd6aad7000)
	libfoo.so => /usr1/tmp/cmake1/build/libfoo.so (0x00007fc5f2ffe000)
libfoo.so:
	statically linked

$ nm -C main | grep "foo\|bar"
                 U bar()

测试INTERFACE

// foo.h
struct A {
	int num1;
	double num2;
};

int foo();

// foo.cpp
#include "foo.h"

int foo()
{
	return sizeof(A);
}

// bar.h
#include "foo.h"

int bar();
int bar()
{
	return 123 * 10;
}

// bar.cpp
#include <iostream>
#include "bar.h"

int main()
{
	std::cout << foo() << std::endl;
	std::cout << bar() << std::endl;
	return 0;
}

// CMakeLists.txt
cmake_minimum_required(VERSION 3.16)

project(foobar)
set(CMAKE_SKIP_RPATH TRUE)

include_directories(${CMAKE_SOURCE_DIR})

add_library(foo SHARED foo.cpp)

add_library(bar SHARED bar.cpp)
target_link_libraries(bar INTERFACE foo)

add_executable(main main.cpp)
target_link_libraries(main bar)

$ ldd *.so
libbar.so:
	statically linked
libfoo.so:
	statically linked

$ nm -C main | grep "foo\|bar"
                 U bar()
                 U foo()