C program issues with function prototype - c

Question

i am reading the C program book written by Denis and i was practicing his examples. I tried this example on my own and then copy pasted the same example from book. I get the followin error.
Code :
#include <stdio.h>
#define MAXLINE 1000 /* maximum input line size */
int getline(char line[], int maxline);
void copy(char to[], char from[]);
/* print longest input line */
main()
{
int len; /* current line length */
int max; /* maximum length seen so far */
char line[MAXLINE]; /* current input line */
char longest[MAXLINE]; /* longest line saved here */
max = 0;
while ((len = getline(line, MAXLINE)) > 0)
if (len > max) {
max = len;
copy(longest, line);
}
if (max > 0) /* there was a line */
printf("%s", longest);
return 0;
}
/* getline: read a line into s, return length */
int getline(char s[], int lim)
{
int c, i;
for (i=0; i<lim-1 && (c=getchar())!=EOF && c!=′\n′; ++i)
s[i] = c;
if (c == ′\n′) {
s[i] = c;
++i;
}
s[i] = ′\0′;
return i;
}
/* copy: copy ′from′ into ′to′; assume to is big enough */
void copy(char to[], char from[])
{
int i;
i = 0;
while ((to[i] = from[i]) != ′\0′)
++i;
}
Error:
ex16.c:4:5: error: conflicting types for 'getline'
int getline(char line[], int maxline);
^
/usr/include/stdio.h:440:9: note: previous declaration is here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE * __restrict) __OSX_AVAILABLE_...
^
ex16.c:8:1: warning: type specifier missing, defaults to 'int' [-Wimplicit-int]
main()
^~~~
ex16.c:16:40: error: too few arguments to function call, expected 3, have 2
while ((len = getline(line, MAXLINE)) > 0)
~~~~~~~ ^
/usr/include/stdio.h:440:1: note: 'getline' declared here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE * __restrict) __OSX_AVAILABLE_...
^
ex16.c:27:5: error: conflicting types for 'getline'
int getline(char s[], int lim)
^
/usr/include/stdio.h:440:9: note: previous declaration is here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE * __restrict) __OSX_AVAILABLE_...
^
1 warning and 3 errors generated.
I am using function prototype correctly only i guess. Refered other internet sources also. I am not sure if its because of compiler. I am using Gcc version 4.3 i guess. OS - mac maverics.
Can you please help me ?
Thanks.

Answer 1

Just call your function getlineMy() in the places where you declare, define and use it.
getline() is already declared in stdio.h (link) and its implementation will be linked to your program so you cannot use that name unless you do tricks.

Answer 2

You have to set GCC to compile your code as C.
gcc -std=c99 -pedantic-errors -Wall
You will then get one error:
8:1: error: return type defaults to 'int'
This is because you are using the wrong definition for main(). Correct it to int main().
The name getline is just fine to use, there is no such function in stdio.h and the compiler is not allowed to add functions that are non-standard extensions inside that header, without naming them with a _ prefix.