char pointer in C not getting the good value

Question

I want to create a function that takes a char or a string in C, so i the argument of the function is a char pointer.

int code(char* mot){
    char alphabet[] = "abcdefghijklmnopqrstuvwxyz";
    if (strlen(mot) > 1){
        // If we give a word
        int longueur = strlen(mot);
        int resultat = 0;
        for (int i=1; i<longueur+1; i++){
            char l = mot[i-1];
            printf("%c\n", l);
            resultat += pow(26, (i-1))*code(&l);
        }
        return resultat;
    } else if (strlen(mot) == 1){
        // If we give a char
        char letter = *mot;
        char* pPosition = strchr(alphabet, letter);
        int index;
        if (pPosition != NULL){
            index = pPosition - alphabet + 1;         
        }
        return index;
    } else {
        printf("ERROR: length of word not valid");
        return -1;
    }
}

My function works if I replace resultat += pow(26, (i-1))*code(&l); with that resultat += pow(26, (i-1))*code("a");. I don't understand why when I use the pointer it don't take the char associated with the pointer. Altough, it displays me a segmentation fault error.

Answer 1

@Barmar answered my question in comment.

it was the strlen function that cannot be used for char type. I will create two different functions to resolve the problem.

Thank you @Barmar , @001 and @Ian Abott for your time.