memcpy，分段错误

Question

i have try to write this code, but i have found a problem with segmentation fault with memcpy ( i have try to see the code with debug)

        FILE *tp;
        int l = 0;
        while ((fgets(buffer, sizeof buffer, tp))) {
            // search equal sign
            char *equalsign = strchr(buffer, '=');
            l++;
            // search quote near value
            char *q1 = equalsign + 1;
            char *q2 = strchr(q1 + 1, '"');
            // extract name and value
            char* names = strndup(buffer, equalsign - buffer);
            char* values = strndup(q1 + 1, q2 - q1 - 1);
            memcpy(g_names,names,strlen(names));
            memcpy(g_values,values,strlen(values));
            free(names);
            free(values);
            }

with

const char* g_names[SIZE] = { 0, };
char* g_values[SIZE] = { 0, };
char buffer[MAXLINE] = {0,};

define as global. with the debug i have see that the problem is with memcpy (segmentation fault). anyone have a suggest? Thanks. Regards.

Answer 1

There are at least two problems with your code: First, it is using g_names as the destination of memcpy , which copies the characters over the array of pointers. You should be copying to g_names[l] (assuming l was to be the index in the g_names array).

Second, your code is missing the actual allocation of g_names[l] , something like:

g_names[l] = malloc(strlen(names) + 1);

But since you're calling strndup anyway, you can simply store the result of that call into the array:

        // search for equal sign
        char *equalsign = strchr(buffer, '=');
        // search quote near value
        char *q1 = equalsign + 1;
        char *q2 = strchr(q1 + 1, '"');
        // extract name and value
        g_names[l] = strndup(buffer, equalsign - buffer);
        g_values[l] = strndup(q1 + 1, q2 - q1 - 1);
        l++;