下面的虚拟机正在堆栈增量指令处分段,该指令从bin指针获取堆栈偏移量并将其增量一。如果我使用值-1,这将正常工作,但是当我通过-1偏移访问bp[1]时,它将崩溃。这对我来说真的没有意义,我做错什么了?

#include <stdio.h>
#include <stdint.h>
#include <unistd.h>

typedef enum {PUSH,STACKINC,EXIT} opCodes;
char * opCode[] =  {"Push","Stack Increment","Exit"};

typedef struct VirtualMachine
{
    uint32_t * sp;          /* Stack Pointer   */
    uint32_t * bp;          /* Bin Pointer     */
    uint32_t stack[100];    /* VM stack        */
} VM;

void processVM(VM * vm)
{
    uint32_t * bp = vm->bp;
    uint32_t * sp = vm->sp;
    printf("OP: %s\n",opCode[bp[0]]);

    switch (bp[0])
    {
    case PUSH:      sp[0] = bp[1]; sp++; bp+=2;     break;
    case STACKINC:  sp[bp[1]]++; bp+=2;             break;
    }

    vm->bp = bp;
    vm->sp = sp;
    /* Set out stack and bin pointers back */
}


int main()
{
    uint32_t binFile[] = {PUSH,1,PUSH,2,PUSH,3,STACKINC,-1,EXIT};

    VM myVM;
    myVM.bp = binFile;
    myVM.sp = myVM.stack;

    while(myVM.bp[0] != EXIT)
    {
            processVM(&myVM);
            usleep(200000);
    }
    printf("VM done executing\n");
}

最佳答案

所有变量都是无符号的。即使你存储-1,当你读回来的时候你也会得到4294967295。

关于c - Mico C虚拟机分段故障,我们在Stack Overflow上找到一个类似的问题:https://stackoverflow.com/questions/10862622/

10-12 16:08