What does my error message mean? - c

Question

/tmp/ccpGLxUa.o: In function `Janitor':
digenv2.c:(.text+0x656): undefined reference to `WIFEEXITED'
collect2: error: ld returned 1 exit status
I'm trying to compile a file that worked before. Now I get thi error message when compiling. The full program is
#include <errno.h>
#include <stdarg.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <unistd.h>
#include <signal.h>
pid_t foreground = -1;
struct command
{
char * const *argv;
};
static _Noreturn void err_syserr(char *fmt, ...)
{
int errnum = errno;
va_list args;
va_start(args, fmt);
vfprintf(stderr, fmt, args);
va_end(args);
if (errnum != 0)
fprintf(stderr, "(%d: %s)\n", errnum, strerror(errnum));
exit(EXIT_FAILURE);
}
/* Helper function that spawns processes */
static int spawn_proc(int in, int out, struct command *cmd)
{
pid_t pid;
if ((pid = fork()) == 0)
{
if (in != 0)
{
if (dup2(in, 0) < 0)
err_syserr("dup2() failed on stdin for %s: ", cmd->argv[0]);
;
close(in);
}
if (out != 1)
{
if (dup2(out, 1) < 0)
err_syserr("dup2() failed on stdout for %s: ", cmd->argv[0]);
close(out);
}
fprintf(stderr, "%d: executing %s\n", (int)getpid(), cmd->argv[0]);
execvp(cmd->argv[0], cmd->argv);
err_syserr("failed to execute %s: ", cmd->argv[0]);
}
else if (pid < 0)
err_syserr("fork failed: ");
return pid;
}
/* Helper function that forks pipes */
static void fork_pipes(int n, struct command *cmd)
{
int i;
int in = 0;
int fd[2];
for (i = 0; i < n - 1; ++i)
{
pipe(fd);
spawn_proc(in, fd[1], cmd + i);
close(fd[1]);
in = fd[0];
}
if (dup2(in, 0) < 0)
err_syserr("dup2() failed on stdin for %s: ", cmd[i].argv[0]);
fprintf(stderr, "%d: executing %s\n", (int)getpid(), cmd[i].argv[0]);
execvp(cmd[i].argv[0], cmd[i].argv);
err_syserr("failed to execute %s: ", cmd[i].argv[0]);
}
int main(int argc, char **argv)
{
int i;
if (argc == 1) /* There were no arguments */
{
char *printenv[] = { "printenv", 0};
char *sort[] = { "sort", 0 };
char *less[] = { "less", 0 };
struct command cmd[] = { {printenv}, {sort}, {less} };
fork_pipes(3, cmd);
}
else
{
if (strcmp(argv[1], "cd") == 0) /* change directory */
{
printf("change directory to %s\n", argv[2]);
chdir(argv[2]);
}
else if (strcmp(argv[1], "exit") == 0)
{
printf("exit\n");
exit(0);
}
else
{
char *tmp;
int len = 1;
for (i = 1; i < argc; i++)
{
len += strlen(argv[i]) + 2;
}
tmp = (char *) malloc(len);
tmp[0] = '\0';
int pos = 0;
for (i = 1; i < argc; i++)
{
pos += sprintf(tmp + pos, "%s%s", (i == 1 ? "" : "|"), argv[i]);
}
char *printenv[] = { "printenv", 0};
char *grep[] = { "grep", "-E", tmp, NULL};
char *sort[] = { "sort", 0 };
char *less[] = { "less", 0 };
struct command cmd[] = { {printenv}, {grep}, {sort}, {less} };
fork_pipes(4, cmd);
free(tmp);
}
}
return(0);
}
/*Remove zoombie processes*/
/*Return if background process terminated*/
/*
http://pubs.opengroup.org/onlinepubs/9699919799/basedefs/signal.h.html
*/
void Janitor(int signal) {
if(signal==SIGCHLD) { /*Child process terminated, stopped, or continued*/
int a = 1;
while(a) {
pid_t pid_my1 = waitpid(-1, &signal, WNOHANG);
/*WNOHANG = return immediately if no child has exited*/
/*http://linux.die.net/man/2/waitpid*/
if(0<pid_my1) { /*Still things to clean up*/
if(pid_my1!=foreground) { /*Don't stop me since it's the foregound process*/
/*http://linux.die.net/man/3/wait*/
if(WIFEEXITED(signal)) { /*Child process terminated*/
/*FIXME*/
}
}
}
else { /*All work done, for now*/
a = 0;
}
}
}
}
The program was compiling fine just a few days ago. It is in a github repository. I compiled, added, commit and pushed and then when I check it out I get the above error message when compiling. Why?

Answer 1

You haven't included the necessary headers for wait(2) options:
#include <sys/types.h>
#include <sys/wait.h>