I am building an application that will used shared memory and I have tried
to compile the attached source file. I have version 3.4.4-3 of the gcc
compiler and appropriate support libraries.
If I use a simple gcc command it complains
$ gcc -Wall -Werror writer.c
writer.c: In function `main':
writer.c:34: warning: implicit declaration of function `shm_open'
writer.c:85: warning: implicit declaration of function `shm_unlink'
------------------------------------------------------- Source file
-----------------------------------------------------
/*
** These examples use semaphores to ensure that writer and reader
** processes have exclusive, alternating access to the shared-memory
region.
*/
/********** writer.c ***********/
#include <unistd.h>
#include <stdlib.h>
#include <stdio.h>
#include <semaphore.h>
#include <errno.h>
#include <sys/types.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/fcntl.h>
char shm_fn[] = "my_shm";
char sem_fn[] = "my_sem";
/**** WRITER ****/
int main(){
caddr_t shmptr;
unsigned int mode;
int shmdes, index;
sem_t *semdes;
int SHM_SIZE;
mode = S_IRWXU|S_IRWXG;
/* Open the shared memory object */
if ( (shmdes = shm_open(shm_fn,O_CREAT|O_RDWR|O_TRUNC, mode)) == -1 ) {
printf("shm_open failure");
exit(1);
}
/* Preallocate a shared memory area */
SHM_SIZE = 4096;
if(ftruncate(shmdes, SHM_SIZE) == -1){
printf("ftruncate failure");
exit(1);
}
if((shmptr = mmap(0, SHM_SIZE, PROT_WRITE|PROT_READ, MAP_SHARED,
shmdes,0)) == (caddr_t) -1){
printf("mmap failure");
exit(1);
}
/* Create a semaphore in locked state */
semdes = sem_open(sem_fn, O_CREAT, 0644, 0);
if(semdes == (void*)-1){
printf("sem_open failure");
exit(1);
}
/* Access to the shared memory area */
for(index = 0; index < 100; index++){
printf("write %d into the shared memory shmptr[%d]\n", index*2, index);
shmptr[index]=index*2;
}
/* Release the semaphore lock */
sem_post(semdes);
munmap(shmptr, SHM_SIZE);
/* Close the shared memory object */
close(shmdes);
/* Close the Semaphore */
sem_close(semdes);
/* Delete the shared memory object */
shm_unlink(shm_fn);
exit(0);
return 0;
}
------------------------------------------------------- End Source file
-----------------------------------------------------
I tried searching for shm_open in my version of the /cygwin/usr/include
directory and did not find either the shm_open or shm_unlink prototypes
defined.
In looking through the FAQ I came across this link
http://cygwin.com/ml/cygwin-cvs/2007-q1/msg00071.html
which suggests to me that I need an update on my header files and perhaps
the dll. Is this update available now and if not, when will it be? How do
I acquire these changes?
Thanks
Don Marquardt
604 273 5131 X 810
