three indirection pointer how to change indirected string's index character -- three indirectio-CodePudding

I have a function like this void tm(char ***path) can u please tell how to change second character of string that I am getting in tm(char ***path) function from some other function

int handle_process(struct connection *con_obj,char **path,char **request_type)
{
    tm(&path)
}

void tm(char ***path)
{
    
    **(*path 1)='x';
}

and print the updated path string in handle_process function. I am getting segFault

CodePudding user response：

It is easier to understand if you split it into more than one operation (to be more difficult second character of the second string):

void tm(char ***path)
{
    char **twoStars = *path;
    char *singleStar = twoStars[1];
    singleStar[1] = 'x';
}

void tm1(char ***path)
{
    (*((*path)   1))[1] = 'z';
}

//or only pointer arithmetic
void tm2(char ***path)
{
    *(*((*path)   1) 1) = '0';
}

//or only indexes 
void tm3(char ***path)
{
    path[0][1][1] = 'z';
}



int main(void)
{
    char str1[] = "hello";
    char str2[] = "world";

    char **strings =  (char *[]){str1, str2};

    printf("string1 = `%s`, string2 = `%s`\n", strings[0], strings[1]);
    tm(&strings);
    printf("string1 = `%s`, string2 = `%s`\n", strings[0], strings[1]);
    tm1(&strings);
    printf("string1 = `%s`, string2 = `%s`\n", strings[0], strings[1]);
}

https://godbolt.org/z/o1aqvT913

and the result:

string1 = `hello`, string2 = `world`
string1 = `hello`, string2 = `wxrld`
string1 = `hello`, string2 = `wzrld`

EDIT (OP comments):

example of the "chained" calls to functions increasing level of indirection

void tm(char ***path)
{
    *(*((*path)   0) 1) = '0';
}
void bar(char **ptr)
{
    tm(&ptr);
}

void foo(char *str)
{
    bar(&str);
}


int main(void)
{
    char str1[] = "hello";

    foo(str1);
    printf("string1 = `%s`\n", str1);
}

https://godbolt.org/z/oxGYonsxz