CPP预处理器到C预处理器转换问题

Question

编辑：标题可能应该是“预编译器，CPP编译器到C编译器转换问题。正如我已经意识到的那样，预处理器是相同的。我认为问题就是那个预处理代码被编译的结果，CPP与C编译器相比，布局更快乐。

关于如何使其兼容C预处理器的任何建议？我试图为一个状态机创建一个灵活的switch语句，这种语句有时会被调用，并在满足特定条件时前进。一旦它到达switch语句的末尾，它通过返回true来表示状态机已完成。我希望能够交换/插入步骤而无需重新分配案例值，所以这就是我在CPP中提出的，这非常有效。

#include <iostream>
#include <thread>

#define DYNCOUNT(start) (__COUNTER__-start)

#define DYNAMIC_SWITCH_BEGIN(identifier,switchElement) \
    const unsigned int identifier = __COUNTER__; \
    switch(switchElement){ \
        case 0:

#define DYNAMIC_SWITCH_ELM(identifier) \
    break; \
    case DYNCOUNT(identifier):

#define DYNAMIC_SWITCH_END \
    break; \
    };


bool stateMachine(unsigned int & state) {

    DYNAMIC_SWITCH_BEGIN(ident, state)
        std::cout << "A" << std::endl;
    //if(some_condition){
    state++;
    //}
    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "B" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "C" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "D" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "E" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "F" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM(ident)
        std::cout << "G" << std::endl;
    //if(some_condition){
    state++;
    //}
    break;
        default:
            return true;
            DYNAMIC_SWITCH_END

                return false;
                //Visual Studios gets confused with the layout and structures it with this tabulation. 
}

int main() {

    unsigned int machineState=0;
    while(!stateMachine(machineState)){/*other operations*/}

    std::this_thread::sleep_for(std::chrono::seconds(5));
    return 0;
}

但是，当我尝试通过MPLAB在C环境中运行它时，我得到：

stateMachines.c：28：9：错误：case标签不会减少为整数常量DYNAMIC_SWITCH_ELM（ident）

因此，CPP预处理器似乎愿意将const unsigned int值解释为其命令，而C预处理器或至少MPLAB的C预处理器则不然。

我唯一的选择是删除DYNAMIC_SWITCH_BEGIN调用的一些内容，而是放置一个

#define ident __COUNT__ 

在开关的开头。哪个也有效，但我试图获得更强制的结构布局。

Answer 1

感谢@EricPostpischil引导我找到这个解决方案。即使案例值正在调整，开关也会表现为从0开始。由于它在幕后，因此案例值不以0开头并不重要。

#include <iostream>
#include <thread>

#define DYNCOUNT(start) (__COUNTER__-start)

#define DYNAMIC_SWITCH_BEGIN(switchElement) \
    switch((switchElement + (__COUNTER__+1))){ \
        case __COUNTER__:

#define DYNAMIC_SWITCH_ELM \
    break; \
    case __COUNTER__:

#define DYNAMIC_SWITCH_END \
    break; \
    };


bool stateMachine(unsigned int & state) {

    DYNAMIC_SWITCH_BEGIN(state)
        std::cout << "A" << std::endl;
    //if(some_condition){
    state++;
    //}
    DYNAMIC_SWITCH_ELM
        std::cout << "B" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "C" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "D" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "E" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "F" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "G" << std::endl;
    //if(some_condition){
    state++;
    //}
    break;
        default:
            return true;
            DYNAMIC_SWITCH_END

                return false;
}

bool stateMachine_2(unsigned int & state) {

    DYNAMIC_SWITCH_BEGIN(state)
        std::cout << "H" << std::endl;
    //if(some_condition){
    state++;
    //}
    DYNAMIC_SWITCH_ELM
        std::cout << "I" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "J" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "K" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "L" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "M" << std::endl;
    //if(some_condition){
    state++;
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "N" << std::endl;
    //if(some_condition){
    state++;
    //}
    break;
        default:
            return true;
            DYNAMIC_SWITCH_END

                return false;
}

int main() {

    unsigned int machineState=0;
    while(!stateMachine(machineState)){}
    machineState = 0;
    while (!stateMachine_2(machineState)) {}

    std::this_thread::sleep_for(std::chrono::seconds(5));
    return 0;
}

编辑：

对于任何有兴趣的人，我在我的原始代码中添加了一些额外的有用工具，因此它不仅可以用于逐步推进状态机，还可以包含循环返回或在状态机更高级时跳转。仍然允许在任何需要的地方复制，粘贴或插入项目，并保持目标。

#define DYNAMIC_SWITCH_BEGIN(elementType,switchElement) \
    do{ \
    const elementType DYNAMIC_SWITCH_OFFSET=__COUNTER__+1; \
    elementType * __DYNAMIC_SWITCH_MODIFY_TARGET = & switchElement; \
    int __DYNAMIC_JUMP_FLAG=0; \
    switch((switchElement + DYNAMIC_SWITCH_OFFSET)){ \
        case __COUNTER__:

#define DYNAMIC_SWITCH_ELM \
    break; \
    case __COUNTER__:

#define DYNAMIC_ADV (*__DYNAMIC_SWITCH_MODIFY_TARGET)++;

#define DYNAMIC_SWITCH_DFLT \
    break; \
    default:

#define DYNAMIC_SWITCH_JUMP(jumpTag) \
    __DYNAMIC_JUMP_FLAG=1; \
    goto jumpTag;

#define DYNAMIC_SWITCH_TAGGED_ELM(jumpTag) \
    break; \
    case __COUNTER__: \
    case (__COUNTER__ +1): \
    jumpTag: \
    (*__DYNAMIC_SWITCH_MODIFY_TARGET) = __COUNTER__ - DYNAMIC_SWITCH_OFFSET; \
    if(__DYNAMIC_JUMP_FLAG)break; //Force to exit and complete on next loop for consistency in stepping behavior.

#define DYNAMIC_SWITCH_END \
    break; \
    }; \
    }while(0);

bool stateMachine(unsigned int & state) {

    DYNAMIC_SWITCH_BEGIN(unsigned int, state)
        std::cout << "A" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}
    DYNAMIC_SWITCH_ELM
        std::cout << "B" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "C" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "D" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "E" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "F" << std::endl;
    DYNAMIC_SWITCH_JUMP(tag1)
    //if(some_condition){
    DYNAMIC_ADV
    //}

    DYNAMIC_SWITCH_ELM
        std::cout << "G" << std::endl;
    //if(some_condition){
    DYNAMIC_ADV
    //}
    DYNAMIC_SWITCH_TAGGED_ELM(tag1)
        std::cout << "H" << std::endl;
    DYNAMIC_ADV

    DYNAMIC_SWITCH_ELM
        std::cout << "I" << std::endl << std::endl;;
    //if(some_condition){
    DYNAMIC_ADV

    DYNAMIC_SWITCH_DFLT
        return true;
    DYNAMIC_SWITCH_END
        return false;
}