为什么在此程序中出现分段错误？

Question

I'm trying to set the values of M and N in this program to whatever is parsed from a string that this C program receives on it's command line. However, I'm getting a segmentation fault whenever I run the code. I'm new to the concept of pointer in C, so I know it's something there.

The code is supposed to work as follows:

./a.out -1,12

Prints:

1, 12

Thanks for any help!

    #include <stdio.h>
    #include <stdlib.h>

    void getnumber(char *toTest, int *a, int *c);

    int main ( int argc, char *argv[] )
    {

            int a, c, curr; 

            a = 1;
            c = 1;
            curr = 1;

            if ( argv[1][0] == '-' )
            {
                    curr = 2;
                    getMandNValues(argv[1], &a, &c);
            }

            printf("%d, %d\n", a, c);
            return 0;
    }


    void getMandNValues(char *src, int *a, int *c)
    {

            char aString[sizeof src];
            char bString[sizeof src];

            int i = 0;

            while((aString[i] = &src[i+1]) != ',')
                    ++i;

            aString[i] = '\0';

            int j = 0;

            while((bString[j] = &src[i + 2]) != '\0')
            {
                    ++j;
                    ++i;
            }

            bString[j] = '\0';

            *a = atoi(aString);
            *c = atoi(bString);
    }

The compiler output is:

/tmp/foo.c: In function ‘main’:
/tmp/foo.c:18: warning: passing argument 2 of ‘getMandNValues’ makes pointer from integer without a cast
/tmp/foo.c:18: warning: passing argument 3 of ‘getMandNValues’ makes pointer from integer without a cast
/tmp/foo.c: In function ‘getMandNValues’:
/tmp/foo.c:34: warning: assignment makes integer from pointer without a cast
/tmp/foo.c:41: warning: assignment makes integer from pointer without a cast

Answer 1

Did not look at everything but you need the address of the vars for this call.

getMandNValues(argv[1], &a, &c);

I don't know what compiler you are using but I would not ignore the warning it must have displayed at compile. (If you are not using the highest level of warning you should.)

---

Looking some more there is another problem

while((aString[i] = &src[i+1]) != ',')
   ++i;

Seems strange (and wrong). I would do this:

int index=0;
do
{
  aString[index] = src[index+1];
  index++;
} while (str[index] != ',')

---

here is another problem

char aString[len(src)];
char bString[len(src)];

Answer 2

getMandNValues(argv[1], a, c);

应该

getMandNValues(argv[1], &a, &c);

Answer 3

您应该将＆a和＆c传递给该函数。

Answer 4

You're mixing getnumber and getMandNvalues .

You've supplied a prototype for getnumber but no definition of that function. You supplied a definition of getMandNvalues but no prototype before you call this function.

Calling a function with no prototype in scope is legal. The compiler assumes it returns int and all arguments are int . Neither of these is true in this case.

Correct your prototype

Answer 5

You pass the int a and int c to the function that expects the int* a and int* c

instead of using

getMandNValues(argv[1], a, c);

, try

getMandNValues(argv[1], &a, &c);