avoid deleting share memory segment if someone is still attached

svn path=/trunk/externals/share_mem/; revision=17353

1 files changed, 17 insertions, 3 deletions

diff --git a/shmem.c b/shmem.c
index 72faa7d..f0e794a 100644
--- a/shmem.c
+++ b/shmem.c
@@ -8,7 +8,7 @@
   #include <tchar.h>
 #else
   #include <sys/shm.h>
-  #include <sys/stat.h>

+  #include <sys/stat.h>
 #endif // _WIN32
 
 typedef struct shmem
@@ -317,8 +317,22 @@ void shmem_free(t_shmem *x)
   if ( x->share_memory ) UnmapViewOfFile( x->share_memory );

   if ( x->m_MapFile ) CloseHandle( x->m_MapFile );

 #else
-	shmdt (x->share_memory);
-	shmctl (x->segment_id, IPC_RMID, 0);

+  if ( x->share_memory ){
+    if ( shmdt (x->share_memory) == -1) error("shmdt failed at %x", x->share_memory);
+  }
+  x->share_memory=NULL;
+  
+  int shm_id = x->segment_id;
+  struct shmid_ds shm_desc;
+  if(shm_id>0){
+    if (shmctl(shm_id,IPC_STAT, &shm_desc) != -1){
+      if(shm_desc.shm_nattch<=0){
+        if (shmctl(shm_id,IPC_RMID, &shm_desc) == -1) error("shmctl remove failed for %d", shm_id);
+      }
+    }
+  }
+  shm_id=0;
+	//~shmctl (x->segment_id, IPC_RMID, 0);

 #endif // _WIN32
 }