1
//代碼段1thread_specific_ptr多線程混亂
static boost::thread_specific_ptr<StreamX> StreamThreadSpecificPtr;
void thread_proc() {
StreamX * stream = NULL;
stream = StreamThreadSpecificPtr.get();
if (NULL == stream) {
stream = new StreamX();
StreamThreadSpecificPtr.reset(stream);
}
printf("%p\n", stream);
}
int run() {
boost::thread_group threads;
for(int i = 0; i < 5; i ++) {
threads.create_thread(&thread_proc);
}
threads.join_all();
}
// the result is
0x50d560 -- SAME POINTER
0x50d540
0x50bfc0
0x50bef0
0x50d560 -- SAME POINTER
//代碼段2
static boost::thread_specific_ptr<StreamX> StreamThreadSpecificPtr(NULL); // DIFF from code snippet 1
void thread_proc() {
StreamX * stream = NULL;
stream = StreamThreadSpecificPtr.get();
if (NULL == stream) {
stream = new StreamX();
StreamThreadSpecificPtr.reset(stream);
}
printf("%p\n", stream);
}
int run() {
boost::thread_group threads;
for(int i = 0; i < 5; i ++) {
threads.create_thread(&thread_proc);
}
threads.join_all();
}
// the result is
0x50d510
0x50d4f0
0x50bf70
0x50ca70
0x50be50
在代碼段1中,兩個指針相同。它不是預期的。 在代碼片段2中,初始化StreamThreadSpecificPtr爲NULL時,所有接縫都很好。
請您幫忙弄清楚這個困惑的答案嗎?非常感謝。
總是高興地看到你的答案。 –