undefined reference to `_fcloseall' - c

Question

I am having trouble compiling my program.
The error message is: undefined reference to `_fcloseall', I think it could be a missing library file at the beginning. It might be also useful to know that I am programming on Windows 8.1 + Cygwin. Which library could be missing or do you see any other mistake?
Here is the code:
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
void cleanup1();
void cleanup2();
int main(int argc, char *argv[])
{
FILE * file;
if(argc < 2){
printf("\ncommand bsp10085 <file>");
exit(1);
}
assert(atexit(cleanup1) == 0);
assert(atexit(cleanup2) == 0);
if((datei = fopen(argv[1], "r")) != NULL){
printf("\nfile %s is being processed ..",argv[1]);
fclose(datei);
}
else
printf("\nfile '%s' is missing. ", argv[1]);
}
void cleanup1(){
printf("\nCleanup the rest");
}
void cleanup2(){
printf("\nClose all open files");
fflush(NULL);
_fcloseall();
}

Answer 1

I tried to compile your code (in ubuntu though) and i also got a warning: warning: implicit declaration of function ‘fcloseall’ [-Wimplicit-function-declaration] fcloseall();
I think that if you add
#define _GNU_SOURCE
before
#include<stdio.h>
your program should work fine. This is your code after i changed some other warnings as well:
#define _GNU_SOURCE
#include <stdio.h>
#include <assert.h>
#include <stdlib.h>
void cleanup1();
void cleanup2();
int main(int argc, char *argv[])
{
FILE *datei;
if(argc < 2){
printf("\ncommand bsp10085 <file>");
exit(1);
}
assert(atexit(cleanup1) == 0);
assert(atexit(cleanup2) == 0);
if((datei = fopen(argv[1], "r")) != NULL){
printf("\nfile %s is being processed ..",argv[1]);
fclose(datei);
}
else
printf("\nfile '%s' is missing. ", argv[1]);
return 0;
}
void cleanup1(){
printf("\nCleanup the rest");
}
void cleanup2(){
printf("\nClose all open files");
fflush(NULL);
fcloseall();
}