I create a shared memory by using shmget. And attach to it by using shmat.

Finally, I use shmctl to get statistics to learn number of attachments to
that shared memory. According to documentation (linux.die.net/man/2/shmat), number of attachments should be 1.

Same codes, C returns 1, D returns 0. It took me 2 days until realising this.

I put C and D codes, and makefile for quick testing.

Ubuntu 64-bit. Kernel: 3.13.0-44-generic

I checked the shmid_ds at both "core.sys.posix.sys.shm" and "/usr/include/bits/shm.h". They look similar. Although C definition makes a difference based on 32 and 64 bits, D's definition doesn't care about. Because I am on 64-bit kernel, they should be same.



main.c
==========================
#include <stdio.h>
#include <sys/types.h>
#include <sys/ipc.h>
#include <sys/shm.h>
#include <fcntl.h>

void main(){
	// allocate
	int id = shmget( IPC_PRIVATE, 4096, IPC_CREAT | S_IRUSR | S_IWUSR );

	// if failed, leave
	if( id == -1 ){
		printf("shmget failed\n");
		return;
	}

	// attach
	void* ptr = shmat( id, 0, 0 );

	// if failed, leave
	if( ptr == (void*)-1 ){
		printf("shmat failed\n");
		shmctl( id, IPC_RMID, 0 );
		return;
	}

	// stat
	struct shmid_ds stat;

	// get statistics
	int res = shmctl( id, IPC_STAT, &stat );
	printf("STAT: %d\n", res);

	// get number of attachments
	printf("NATTCH: %d\n", (unsigned short)stat.shm_nattch);

	// detach
	shmdt( ptr );

	// remove
	shmctl( id, IPC_RMID, 0 );
}


main.d
===============================
import std.stdio;

private import core.sys.posix.sys.mman;
private import core.sys.posix.sys.shm;
private import core.sys.posix.unistd;
private import core.sys.posix.sys.stat;
private static import core.stdc.errno;
private static import core.stdc.time;

void main(){
	// allocate
	int id = shmget( IPC_PRIVATE, 4096, IPC_CREAT | S_IRUSR | S_IWUSR );

	// if failed, leave
	if( id == -1 ){
		writeln("shmget failed");
		return;
	}

	// attach
	void* ptr = shmat( id, null, 0 );

	// if failed, leave
	if( ptr == cast(void*)-1 ){
		writeln("shmat failed");
		shmctl( id, IPC_RMID, null );
		return;
	}

	// stat
	shmid_ds stat;

	// get statistics
	int res = shmctl( id, IPC_STAT, &stat );
	writeln("STAT: ", res);

	// get number of attachments
	writeln("NATTCH: ", stat.shm_nattch);

	// detach
	shmdt( ptr );

	// remove
	shmctl( id, IPC_RMID, null );
}



makefile
==============================
all:
	dmd main.d -of"dprog"
	gcc main.c -o cprog

clear:
	rm cprog
	rm dprog

On Sunday, 18 January 2015 at 16:06:39 UTC, tcak wrote:
> I create a shared memory by using shmget. And attach to it by using shmat.
>
> Finally, I use shmctl to get statistics to learn number of attachments to
> that shared memory. According to documentation (linux.die.net/man/2/shmat), number of attachments should be 1.
>
> Same codes, C returns 1, D returns 0. It took me 2 days until realising this.
>
> I put C and D codes, and makefile for quick testing.
>
> Ubuntu 64-bit. Kernel: 3.13.0-44-generic
>
> I checked the shmid_ds at both "core.sys.posix.sys.shm" and "/usr/include/bits/shm.h". They look similar. Although C definition makes a difference based on 32 and 64 bits, D's definition doesn't care about. Because I am on 64-bit kernel, they should be same.
>
>
>
> main.c
> ==========================
> #include <stdio.h>
> #include <sys/types.h>
> #include <sys/ipc.h>
> #include <sys/shm.h>
> #include <fcntl.h>
>
> void main(){
> 	// allocate
> 	int id = shmget( IPC_PRIVATE, 4096, IPC_CREAT | S_IRUSR | S_IWUSR );
>
> 	// if failed, leave
> 	if( id == -1 ){
> 		printf("shmget failed\n");
> 		return;
> 	}
>
> 	// attach
> 	void* ptr = shmat( id, 0, 0 );
>
> 	// if failed, leave
> 	if( ptr == (void*)-1 ){
> 		printf("shmat failed\n");
> 		shmctl( id, IPC_RMID, 0 );
> 		return;
> 	}
>
> 	// stat
> 	struct shmid_ds stat;
>
> 	// get statistics
> 	int res = shmctl( id, IPC_STAT, &stat );
> 	printf("STAT: %d\n", res);
>
> 	// get number of attachments
> 	printf("NATTCH: %d\n", (unsigned short)stat.shm_nattch);
>
> 	// detach
> 	shmdt( ptr );
>
> 	// remove
> 	shmctl( id, IPC_RMID, 0 );
> }
>
>
> main.d
> ===============================
> import std.stdio;
>
> private import core.sys.posix.sys.mman;
> private import core.sys.posix.sys.shm;
> private import core.sys.posix.unistd;
> private import core.sys.posix.sys.stat;
> private static import core.stdc.errno;
> private static import core.stdc.time;
>
> void main(){
> 	// allocate
> 	int id = shmget( IPC_PRIVATE, 4096, IPC_CREAT | S_IRUSR | S_IWUSR );
>
> 	// if failed, leave
> 	if( id == -1 ){
> 		writeln("shmget failed");
> 		return;
> 	}
>
> 	// attach
> 	void* ptr = shmat( id, null, 0 );
>
> 	// if failed, leave
> 	if( ptr == cast(void*)-1 ){
> 		writeln("shmat failed");
> 		shmctl( id, IPC_RMID, null );
> 		return;
> 	}
>
> 	// stat
> 	shmid_ds stat;
>
> 	// get statistics
> 	int res = shmctl( id, IPC_STAT, &stat );
> 	writeln("STAT: ", res);
>
> 	// get number of attachments
> 	writeln("NATTCH: ", stat.shm_nattch);
>
> 	// detach
> 	shmdt( ptr );
>
> 	// remove
> 	shmctl( id, IPC_RMID, null );
> }
>
>
>
> makefile
> ==============================
> all:
> 	dmd main.d -of"dprog"
> 	gcc main.c -o cprog
>
> clear:
> 	rm cprog
> 	rm dprog


Here is what I did to solve the problem. In D code, I defined my own shmid_ds struct (Structure is taken from /usr/include/bits/shm.h)

// from /usr/include/bits/shm.h
/* Type to count number of attaches.  */
alias shmatt_t = c_ulong;

/* Data structure describing a shared memory segment.  */
version( X86_64 ){
	struct my_shmid_ds{
	    ipc_perm shm_perm;		/* operation permission struct */
	    size_t shm_segsz;			/* size of segment in bytes */
	    time_t shm_atime;			/* time of last shmat() */
	    time_t shm_dtime;			/* time of last shmdt() */
	    time_t shm_ctime;			/* time of last change by shmctl() */
	    pid_t shm_cpid;			/* pid of creator */
	    pid_t shm_lpid;			/* pid of last shmop */
	    shmatt_t shm_nattch;		/* number of current attaches */
	    c_ulong __glibc_reserved4;
	    c_ulong __glibc_reserved5;
	};
}
else{
	struct my_shmid_ds{
	    ipc_perm shm_perm;		/* operation permission struct */
	    size_t shm_segsz;			/* size of segment in bytes */
	    time_t shm_atime;			/* time of last shmat() */
	    c_ulong __glibc_reserved1;
	    time_t shm_dtime;			/* time of last shmdt() */
	    c_ulong __glibc_reserved2;
	    time_t shm_ctime;			/* time of last change by shmctl() */
	    c_ulong __glibc_reserved3;
	    pid_t shm_cpid;			/* pid of creator */
	    pid_t shm_lpid;			/* pid of last shmop */
	    shmatt_t shm_nattch;		/* number of current attaches */
	    c_ulong __glibc_reserved4;
	    c_ulong __glibc_reserved5;
	};
}



Then, I changed the type of "stat" variable:

my_shmid_ds stat;



Finally, need to do a casting (Doing this came to me so stupid after writing it in C):

int res = shmctl( id, IPC_STAT, cast( core.sys.posix.sys.shm.shmid_ds* )(&stat) );


After these, it works perfectly. I hope this can be fixed in next version.

On Sunday, 18 January 2015 at 18:07:05 UTC, tcak wrote:
> After these, it works perfectly. I hope this can be fixed in next version.

Please file a bug at <https://issues.dlang.org/>. And since you seem to know how to fix it, maybe you can make a pull request via GitHub, too?

On Sunday, 18 January 2015 at 22:25:39 UTC, anonymous wrote:
> On Sunday, 18 January 2015 at 18:07:05 UTC, tcak wrote:
>> After these, it works perfectly. I hope this can be fixed in next version.
>
> Please file a bug at <https://issues.dlang.org/>. And since you seem to know how to fix it, maybe you can make a pull request via GitHub, too?

https://issues.dlang.org/show_bug.cgi?id=14007

I am not familiar with Github's pull system etc. So, I will prepare the fixed code and attach it on issue.

On Monday, 19 January 2015 at 04:18:47 UTC, tcak wrote:
> On Sunday, 18 January 2015 at 22:25:39 UTC, anonymous wrote:
>> On Sunday, 18 January 2015 at 18:07:05 UTC, tcak wrote:
>>> After these, it works perfectly. I hope this can be fixed in next version.
>>
>> Please file a bug at <https://issues.dlang.org/>. And since you seem to know how to fix it, maybe you can make a pull request via GitHub, too?
>
> https://issues.dlang.org/show_bug.cgi?id=14007
>
> I am not familiar with Github's pull system etc. So, I will prepare the fixed code and attach it on issue.

Fixed shm.d file is put on issue page. If someone could put a pull request on Github with it.

shmid_ds is on version(linux) part is fixed up on it, and works properly. But tested on 64-bit system only.

On 1/19/2015 2:35 PM, tcak wrote:
> On Monday, 19 January 2015 at 04:18:47 UTC, tcak wrote:
>> On Sunday, 18 January 2015 at 22:25:39 UTC, anonymous wrote:
>>> On Sunday, 18 January 2015 at 18:07:05 UTC, tcak wrote:
>>>> After these, it works perfectly. I hope this can be fixed in next
>>>> version.
>>>
>>> Please file a bug at <https://issues.dlang.org/>. And since you seem
>>> to know how to fix it, maybe you can make a pull request via GitHub,
>>> too?
>>
>> https://issues.dlang.org/show_bug.cgi?id=14007
>>
>> I am not familiar with Github's pull system etc. So, I will prepare
>> the fixed code and attach it on issue.
>
> Fixed shm.d file is put on issue page. If someone could put a pull
> request on Github with it.
>

https://help.github.com/articles/creating-a-pull-request/

On Monday, 19 January 2015 at 05:35:46 UTC, tcak wrote:
> Fixed shm.d file is put on issue page. If someone could put a pull request on Github with it.
>
> shmid_ds is on version(linux) part is fixed up on it, and works properly. But tested on 64-bit system only.

Aand it's in: https://github.com/D-Programming-Language/druntime/commit/43199cdb8fa302613ba9f1dd48646083a85cb272