Question

edit：标题可能应该是“预处理器，CPP编译器到C编译器的转换问题。众所周知，预处理器是相同的。我认为问题出在那预处理的代码被编译后，与C编译器相比，CPP在布局方面更快乐。

关于如何使它与C预处理程序兼容的任何建议？我试图以一种巧妙的方式为状态机创建灵活的switch语句，该语句有时会被调用，并且在满足特定条件时会前进。一旦到达switch语句的末尾，它就通过返回true来指示状态机已完成。我希望能够交换/插入步骤而不必重新分配案例值，所以这就是我在CPP中想到的，效果很好。

#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，会得到：

stateMachines.c：28：9：错误：案例标签未减少为整数常量 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预处理器则不这样做。

我唯一的选择是删掉DYNAMIC_SWITCH_BEGIN调用的某些内容，而是放置一个

#define ident __COUNT__

开关开头的

。这也可行，但是我试图获得更强制的结构布局。

Answer 1

请@EricPostpischil指导我使用此解决方案。即使大小写值正在调整，该开关也将表现为从0开始。由于它在幕后，所以case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：

对于那些精打细算的人，我在原始代码中添加了一些其他有用的工具，因此它不仅可以用于逐步推进的状态机，还可以包含环回或向前跳转（以防状态机更高级）。仍然允许根据需要复制和粘贴或插入项目，保持目标不变。

#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;
}

CPP预处理程序到C预处理程序的转换问题

1 个答案: