C++ 根据工具链文件中的定义替换单个函数定义

要解决您的问题，请删除所有预处理器 有关BASE_OPERATION_N的指令并重写源文件，如下所示:

//operations.h

#ifndef OPERATIONS_H
#define OPERATIONS_H

int op_1(int a, int b);
int op_2(int a, int b);

#endif

//base/operations.c

#include <operations.h>

#ifndef CUSTOM_OP_1
int op_1(int a, int b)
{
    return a + b;
}
#endif 

#ifndef CUSTOM_OP_2
int op_2(int a, int b)
{
    return 2 * (a + b);
}
#endif 

// custom/operations.c

#ifdef CUSTOM_OP_2
int op_2(int a, int b)
{
    return 3 * (a + b);
}
#endif

这样，-DCUSTOM_OP_2就足以禁用进制op_2和 启用自定义op_2的编辑.相反，缺席-DCUSTOM_OP_2 足以禁用自定义op_2的编译并启用编译 op_2基数的.

这是一个演示.我的CMake项目是:

$ tree
.
├── base
│   └── operations.c
├── CMakeLists.txt
├── config.cmake
├── custom
│   └── operations.c
├── operations.h
└── test.c

cmake.config是我的工具链文件.它不需要存在 默认构建.我正在构建一个测试程序和一个库来证明这是有效的.为 同样的目的，我在来源中添加了一些printf:

$ cat base/operations.c 
//base/operations.c

#include <stdio.h>
#include <operations.h>

#ifndef CUSTOM_OP_1
int op_1(int a, int b)
{
    printf("%s_%s\n","Base",__func__);
    return a + b;
}
#endif 

#ifndef CUSTOM_OP_2
int op_2(int a, int b)
{
    printf("%s_%s\n","Base",__func__);
    return 2 * (a + b);
}
#endif

$ cat custom/operations.c 
// custom/operations.c
#include <stdio.h>

#ifdef CUSTOM_OP_1
int op_1(int a, int b)
{
    printf("%s_%s\n","Custom",__func__);
    return 3 * (a + b);
}
#endif

#ifdef CUSTOM_OP_2
int op_2(int a, int b)
{
    printf("%s_%s\n","Custom",__func__);
    return 3 * (a + b);
}
#endif

我的CMakeLists.txt是:

$ cat CMakeLists.txt 
cmake_minimum_required(VERSION 3.14)
project(operations)

set(BASE_SOURCES ./base/operations.c)
set(SOURCES ${BASE_SOURCES} ${CUSTOM_SOURCES})
include_directories(./)

add_library(
  operations
  ${SOURCES}
)

add_executable(
    test
    test.c)
    
target_link_libraries(test operations)

默认构建为:

$ mkdir build
$ cd build
$ cmake ..
-- The C compiler identification is GNU 13.2.0
-- The CXX compiler identification is GNU 13.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/imk/develop/so/cmake_prob/build
$ make
[ 25%] Building C object CMakeFiles/operations.dir/base/operations.c.o
[ 50%] Linking C static library liboperations.a
[ 50%] Built target operations
[ 75%] Building C object CMakeFiles/test.dir/test.c.o
[100%] Linking C executable test
[100%] Built target test

该程序运行:

$ ./test
Base_op_1
Base_op_2

现在这是我的工具链文件v.1:

$ cd ..
$ cat config.cmake 
set(CUSTOM_SOURCES ./custom/operations.c)
add_compile_options(-DCUSTOM_OP_2)

我正在禁用Base op_2，启用自定义op_2

激活并重新生成构建系统:

$ cd build
$ rm -fr *
$ cmake -DCMAKE_TOOLCHAIN_FILE=config.cmake ..
-- The C compiler identification is GNU 13.2.0
-- The CXX compiler identification is GNU 13.2.0
-- Detecting C compiler ABI info
-- Detecting C compiler ABI info - done
-- Check for working C compiler: /usr/bin/cc - skipped
-- Detecting C compile features
-- Detecting C compile features - done
-- Detecting CXX compiler ABI info
-- Detecting CXX compiler ABI info - done
-- Check for working CXX compiler: /usr/bin/c++ - skipped
-- Detecting CXX compile features
-- Detecting CXX compile features - done
-- Configuring done (0.2s)
-- Generating done (0.0s)
-- Build files have been written to: /home/imk/develop/so/cmake_prob/build

重建和测试:

$ make && ./test
[ 20%] Building C object CMakeFiles/operations.dir/base/operations.c.o
[ 40%] Building C object CMakeFiles/operations.dir/custom/operations.c.o
[ 60%] Linking C static library liboperations.a
[ 60%] Built target operations
[ 80%] Building C object CMakeFiles/test.dir/test.c.o
[100%] Linking C executable test
[100%] Built target test
Base_op_1
Custom_op_2

有定制op_2.

现在我想恢复到op_2进制并启用自定义op_1.其工具链文件为v.2:

$ cd ..
$ cat config.cmake 
set(CUSTOM_SOURCES ./custom/operations.c)
add_compile_options(-DCUSTOM_OP_1)

现在不需要重新生成构建系统.我可以做:

$ cd build
$ make
-- Configuring done (0.0s)
-- Generating done (0.0s)
-- Build files have been written to: /home/imk/develop/so/cmake_prob/build
[ 20%] Building C object CMakeFiles/operations.dir/base/operations.c.o
[ 40%] Building C object CMakeFiles/operations.dir/custom/operations.c.o
[ 60%] Linking C static library liboperations.a
[ 60%] Built target operations
[ 80%] Building C object CMakeFiles/test.dir/test.c.o
[100%] Linking C executable test
[100%] Built target test
$ ./test
Custom_op_1
Base_op_2

有定制op_1.