K&R Exercise 1-16 clang - conflicting types for getline
c, clang
Solution
The problem is just that your system already provides a function called `getline`. `man getline` should tell you its signature. On my system it's:
ssize_t getline(char ** restrict linep, size_t * restrict linecapp, FILE * restrict stream);
You can either match that or just rename your function to be called 'mygetline' or something like that.
Alternately, if you can avoid including `stdio.h`, you can avoid the problem entirely.
As to your final question:
What options should I pass to Clang when compiling K&R exercises so as to avoid anything else being included?
You can't - the system headers are what they are, and have presumably moved on since K&R was last revised in 1988. There have been multiple C standard updates since then. In some ways K&R is really starting to get long in the tooth.
Problem
I'm working through K&R, using Clang as my compiler. Exercise 1-16 produces the "conflicting types for 'getline'" error when compiled with Clang. I'm guessing because one of the default libraries has a getline function. What options should I pass to Clang when compiling K&R exercises so as to avoid anything else being included? The exercise sample to be modified is: ``` #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; } ``` The errors from Clang when invoked 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. ```