向动态char数组添加反斜杠

Question

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

    arr = (char*)malloc((strlen(argv[1]) + 1) * sizeof(char));//1 additional byte for the backslash.
    strcpy(arr, argv[1]);
    strcat(arr, '\\');

    return 0;
}

After this code I get Access violation reading error.
Basically I'm just trying to append a backslash to a dynamic string that contains the first argument of the program.

Answer 1

This is probably wrong:

arr = (char*)malloc((strlen(argv[1]) + 1) * sizeof(char));

argv[1]+1 is the second argument, if exists. You wanted:

arr = malloc(strlen(argv[1]) + 2);

I simplified this line a lot since sizeof(char) is 1 by definition and adding 2 instead of 1 as you would need additional byte for the nul terminator. Casting malloc is unnecessary .

strcat operates on strings. '\\\\' is not a string. It should be:

strcat(arr, "\\");