K & R Exercise 1-16 clang - conflicting types for getline

Question

I work through K & R, using Clang as my compiler.

Exercise 1-16 creates "conflicting types for a getline error" when compiling with Clang. I assume that one of the libraries has a getline function by default.

What parameters should be passed to the Clan when compiling K & R exercises to avoid including other elements?

Sample exercise to modify:

#include <stdio.h>
#define MAXLINE 1000

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 line lenght 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); /* line -> longest */
    }

  if (max > 0) /* there was a line */
    printf("\n\nLength: %d\nString: %s", max -1, 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;
}

Errors from Clang when called as: cc ex1-16.c -o ex1-16

ex1-16.c:4:5: error: conflicting types for 'getline'
int getline(char line[], int maxline);
    ^
/usr/include/stdio.h:449:9: note: previous declaration is here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE *...
        ^
ex1-16.c:17:38: error: too few arguments to function call, expected 3, have 2
  while ((len = getline(line, MAXLINE)) > 0)
                ~~~~~~~              ^
/usr/include/stdio.h:449:1: note: 'getline' declared here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE *...
^
ex1-16.c:29:5: error: conflicting types for 'getline'
int getline(char s[], int lim)
    ^
/usr/include/stdio.h:449:9: note: previous declaration is here
ssize_t getline(char ** __restrict, size_t * __restrict, FILE *...
        ^
3 errors generated.

Answer 1

The problem is that your system already provides a function called getline. man getlinemust tell you my signature. On my system, this is:

ssize_t getline(char ** restrict linep, size_t * restrict linecapp, FILE * restrict stream);

, , "mygetline" - .

, stdio.h, .

:

K & R, ?

- - , , , K & R 1988 . C. K & R .

Answer 2

: getline " 1 K & R2?

, gcc. , ANSI C, GNU/POSIX.

:

$ clang test.c -ansi 

, ,

$ clang test.c -std=c89

---

:

$ clang --version
clang version 3.3 (tags/RELEASE_33/rc2)
Target: x86_64-redhat-linux-gnu
Thread model: posix

ANSI :

->clang --version
Apple clang version 1.7 (tags/Apple/clang-77) (based on LLVM 2.9svn)
Target: x86_64-apple-darwin10
Thread model: posix