From 4cbd86a058e0be4b5441685497046d2484b9e9bf Mon Sep 17 00:00:00 2001
From: Takuya NAKAOKA <takuyan@google.com>
Date: Mon, 7 Sep 2015 18:59:59 +0900
Subject: [PATCH] Detach posix shared memory correctly

* shmget() fails after shmctl() is called with IPC_RMID. This patch
removes shmget() in releaseSharedMemory so that a client can detach
a shared memory correctly after a server removed it.
* A server should also detach a shared memory.
---
 examples/SharedMemory/PosixSharedMemory.cpp | 16 +++++++++-------
 1 file changed, 9 insertions(+), 7 deletions(-)

diff --git a/examples/SharedMemory/PosixSharedMemory.cpp b/examples/SharedMemory/PosixSharedMemory.cpp
index 0d4a5a878..b4ecad863 100644
--- a/examples/SharedMemory/PosixSharedMemory.cpp
+++ b/examples/SharedMemory/PosixSharedMemory.cpp
@@ -19,10 +19,12 @@
 struct PosixSharedMemoryInteralData
 {
 	bool m_createdSharedMemory;
+	int m_sharedMemoryId;
 	void* m_sharedMemoryPtr;
 	
 	PosixSharedMemoryInteralData()
 	:m_createdSharedMemory(false),
+	m_sharedMemoryId(-1),
 	m_sharedMemoryPtr(0)
 	{
 	}
@@ -66,6 +68,7 @@ void*   PosixSharedMemory::allocateSharedMemory(int key, int size,  bool allowCr
         } else
         {
 			m_internalData->m_createdSharedMemory = allowCreation;
+			m_internalData->m_sharedMemoryId = id;
 			m_internalData->m_sharedMemoryPtr = result.ptr;
             return result.ptr;
         }
@@ -79,16 +82,14 @@ void*   PosixSharedMemory::allocateSharedMemory(int key, int size,  bool allowCr
 void PosixSharedMemory::releaseSharedMemory(int key, int size)
 {
 #ifdef TEST_SHARED_MEMORY
-    int flags = 0666;
-    int id = shmget((key_t) key, (size_t) size,flags);
-    if (id < 0)
+    if (m_internalData->m_sharedMemoryId < 0)
     {
-        b3Error("PosixSharedMemory::releaseSharedMemory: shmget error");
+        b3Error("PosixSharedMemory::releaseSharedMemory: shared memory id is not set");
     } else
     {
 		if (m_internalData->m_createdSharedMemory)
 		{
-			int result = shmctl(id,IPC_RMID,0);
+			int result = shmctl(m_internalData->m_sharedMemoryId,IPC_RMID,0);
 			if (result == -1)
 			{
 				b3Error("PosixSharedMemory::releaseSharedMemory: shmat returned -1");
@@ -97,8 +98,9 @@ void PosixSharedMemory::releaseSharedMemory(int key, int size)
 				b3Printf("PosixSharedMemory::releaseSharedMemory removed shared memory");
 			}
 			m_internalData->m_createdSharedMemory = false;
-			m_internalData->m_sharedMemoryPtr = 0;
-		} else
+			m_internalData->m_sharedMemoryId = -1;
+		}
+		if (m_internalData->m_sharedMemoryPtr)
 		{
 			shmdt(m_internalData->m_sharedMemoryPtr);
 			m_internalData->m_sharedMemoryPtr  = 0;