共享库的代码是模块化的,由几个独立的单元组成。每个单元都内置到静态库中。
unit1.c
#include <stdio.h>
void HelloWorld() {
printf("Hello World!\n");
}
unit2.c
#include <stdio.h>
void GoodbyeWorld() {
printf("Goodbye World!\n");
}
CMakeLists.txt
cmake_minimum_required(VERSION 3.0.2)
add_library(unit1 STATIC unit1.c)
target_compile_options(unit1 PRIVATE -fPIC)
add_library(unit2 STATIC unit2.c)
target_compile_options(unit2 PRIVATE -fPIC)
add_library(merged SHARED)
target_link_libraries(merged unit1 unit2)
set_target_properties(merged PROPERTIES LINKER_LANGUAGE C)
构建步骤:
cmake . && cmake --build .
由libmerged.so导出的符号:
$ nm -D --defined-only libmerged.so
0000000000201020 B __bss_start
0000000000201020 D _edata
0000000000201028 B _end
00000000000005a0 T _fini
0000000000000458 T _init
Q为什么不导出符号HelloWorld和GoodbyeWorld?如何解决?
我尝试--version-script
失败了。
CMakeLists.txt中的其他设置
set_target_properties(merged PROPERTIES LINK_FLAGS -Wl,--version-
script=merged.version)
merged.version
merged {
global: HelloWorld; GoodbyeWorld;
local: *;
};
set_target_properties(merged PROPERTIES LINK_FLAGS -Wl,-force_load,libunit1.a)
一种选择是为OBJECT
和STATIC
创建unit1
而不是unit2
个库。
cmake_minimum_required(VERSION 3.0.2)
add_library(unit1 OBJECT unit1.c)
target_compile_options(unit1 PRIVATE -fPIC)
add_library(unit2 OBJECT unit2.c)
target_compile_options(unit2 PRIVATE -fPIC)
add_library(merged SHARED $<TARGET_OBJECTS:unit1> $<TARGET_OBJECTS:unit2>)
set_target_properties(merged PROPERTIES LINKER_LANGUAGE C)
$ nm -D --defined-only libmerged.so
000000000000065d T GoodbyeWorld
000000000000064a T HelloWorld
0000000000201028 B __bss_start
0000000000201028 D _edata
0000000000201030 B _end
0000000000000670 T _fini
0000000000000520 T _init