Question

Here is my code:

#include<stdio.h>
#define MAXLINE 100

/*print the reverse of the input*/

int getline1(char line[], int maxline);
char *reverse(char);

main(){
    int len;
    char line[MAXLINE];
    char *rp;
    while ((len = getline1(line, MAXLINE)) > 0)
            rp = reverse(line);
            printf("%s", *rp);
    return 0;
}
int getline1(char s[], int lim){
    int c, i;

    for (i = 0; (c=getchar()) != EOF && c != '\n'; i++)
            if (i > lim-1)
                    continue;
            else
                    s[i] = c;
    if (c == '\n'){
            s[i] = c;
            i++;
    }
    s[i] = '\0';
    return i;
}
char *reverse(char ca[]){
    int i;
    int i1 = 0;
    char *rp;
    char reversed[MAXLINE];
    for (i = MAXLINE-1; i >= 0; i--){
            reversed[i1] = ca[i];
            i1++;
    }
    rp = reversed;
    return rp;
}

But when I try to compile it, I get the following errors:

reverse.cpp: In function ‘int main()’:
reverse.cpp:14:20: error: invalid conversion from ‘char*’ to ‘char’ [-fpermissive]
reverse.cpp:7:7: error:   initializing argument 1 of ‘char* reverse(char)’ [-fpermissive]
reverse.cpp:15:19: warning: format ‘%s’ expects argument of type ‘char*’, but argument 2 has type ‘int’ [-Wformat]

I don’t have much experience with C++. What am I doing wrong? I just want to make a pointer to a char array and return it.

Answer 1

I just want to make a pointer to a char array and return it.

You appear to want to return a string. That is not a pointer to a char array. Even if your program compiled, you would invoke UB, as you return a pointer to an automatic object- and there are quite a few other runtime errors in your code as well. You got lucky that you also made a compile-time error so the compiler did not accept your program. This C++ program achieves what you intend:

#include <string>
#include <iostream>

std::string reverse(std::string val) {
    return std::string(val.rbegin(), val.rend());
}
int main() {
    std::string str;
    while(std::getline(std::cout, str))
        std::cout << reverse(str);
}

What am I doing wrong?

You’re learning C89 intead of C++11. They’re really different things.

If you wish to learn to code C++, you must learn std::string, and the rest of the Standard library. You will not get anywhere with char*, char[], and MAGIC_BUFFER_SIZE.