为什么我的 switch case 不起作用？/我该如何修复这些构建错误？

Question

I'm a student and I've written out this code (the task involves controlling an automatic door) I thought I had everything sorted but when I try to build it it gives me a few errors. If someone could point me in the right direction to fixing them that would be great!

#include <reg167.h>
#define SensorsActive P2 & 0x0010 == 0x0010 || P2 & 0x0020 == 0x0020

/* Main program - Automatic doors */

int main(void)
{
    DP2 = 0x0003;
    /* sets bits 0,1 as outputs and the rest as inputs */ 
    ODP2 = 0x0000;
    /* selects output push/pull driver */
    enum {closed, opening, open, closing} state;
    /* define FSM states */
    state = 1;
    /* set starting state as door closed */

    for (;;) {
        switch (state) {
        case closed: /* Door closed */
            if (SensorsActive) {
            /* If motion sensors are activated switch to opening state */
                state = opening;                                        
            }
            break;      
        case opening: /* Door opening */
            P2 = P2 & ~0x0001;
            /* Sets direction bit to clockwise (opening) */
            P2 |= 0x0002;    /* Turns on motor control bit */
            if(P2&0x0004==0x0004)//door open limit switches triggered switch to open
                state = open;
            break;
        case open: /* Door open */
            timer();
            while (T3OTL != 1) ;
            if(SensorsActive) {
            /* If sensors are active break so that open case will be repeated and timer reset... */                                                         /* ...Else switch state to closing */
                    break;
            }
            else state = closing;
            break;
        case closing: /* Door closing */
            P2 |= 0x0001;// Sets direction bit to counterclockwise (closing) 
            P2 |= 0x0002;/* Turns on motor control bit */
            if(SensorsActive)/* If sensors are active start opening doors */ 
                state = opening;
            if(P2 & 0x0008 == 0x0008) {
            //If closed limit switches are reached switch state to closed
                    state = closed;
            }
            break;
        }
    }
}

The errors it is giving are:

Build target 'Target 1'

compiling main.c...

main.c(10): error C25: syntax error near 'enum'

main.c(11): error C53: redefinition of 'state'

main.c(13): error C25: syntax error near 'while'

main.c(13): error C25: syntax error near '1'

main.c(16): error C103: 'state': illegal function definition (missing ';' ?)

Target not created.

Answer 1

It seems you are compiling in C89 mode, where you can't have variable declarations anywhere (it was added in the C99 standard). Move the state declaration to the top of the function.

Alternatively, tell the compiler to use the C99 rules. For GCC this can be done by adding the -std=c99 option to the command line.

---

Right now your code looks like this (comments added by me):

void main(void) {
    DP2 = 0x0003;  /* Assignment, okay */
    ODP2 = 0x0000; /* Another assignment, okay */
    enum {closed, opening, open, closing} state;  /* Variable declaration, NOT okay */
    state = 1; /* Assignment, okay */

    ...
}

You need to put the variable declarations first in the function:

void main(void) {
    enum {closed, opening, open, closing} state;  /* Variable declaration, okay here */

    DP2 = 0x0003;  /* Assignment, okay */
    ODP2 = 0x0000; /* Another assignment, okay */
    state = 1; /* Assignment, okay */

    ...
}