小白学c++のマルチスレッド関数の戻り値

#include 
#include 
#include 
#include 

//pthread_mutex_t lock;
int ticketcount=5;

void* salewinds1(void* args)
{
	while(ticketcount>0)
	{
		printf("window1 start %d
",ticketcount);
		sleep(1);
		ticketcount--;
		printf("sale ticket finish:%d
",ticketcount);
	}
}

void* salewinds2(void* args)
{
	while(ticketcount>0)
	{
		printf("windows2 start:%d
",ticketcount);
		sleep(1);
		ticketcount--;
		printf("sale finish:%d
",ticketcount);
	}
}


int main(int argc,const char* argv[])
{

	pthread_t thd1;
	pthread_t thd2;
	int val1=1;
	int val2=2;
	//pthread_mutex_init(&lock,NULL);
	
	pthread_create(&thd1,NULL,salewinds1,NULL);
	pthread_create(&thd2,NULL,salewinds2,NULL);
	pthread_join(thd1,(void**)&val1);
	pthread_join(thd2,(void**)&val2);

	printf("val1:%d....val2:%d
",val1,val2);
	//pthread_mutex_destroy(&lock);
	return 0;
}

このコードの実行結果は次のとおりです.
windows2 start:5 window1 start 5 sale finish:4 windows2 start:4 sale ticket finish:3 window1 start 3 sale finish:2 windows2 start:2 sale ticket finish:1 window1 start 1 sale finish:0 sale ticket finish:-1 val1:-256....val2:0
val 1とval 2の値がゴミ値になりました

#include 
#include 
#include 
#include 

//pthread_mutex_t lock;
int ticketcount=5;

void* salewinds1(void* args)
{
	while(ticketcount>0)
	{
		printf("window1 start %d
",ticketcount);
		sleep(1);
		ticketcount--;
		printf("sale ticket finish:%d
",ticketcount);
	}
	return NULL;
}

void* salewinds2(void* args)
{
	while(ticketcount>0)
	{
		printf("windows2 start:%d
",ticketcount);
		sleep(1);
		ticketcount--;
		printf("sale finish:%d
",ticketcount);
	}
	return NULL;
}


int main(int argc,const char* argv[])
{

	pthread_t thd1;
	pthread_t thd2;
	int val1=1;
	int val2=2;
	//pthread_mutex_init(&lock,NULL);
	
	pthread_create(&thd1,NULL,salewinds1,NULL);
	pthread_create(&thd2,NULL,salewinds2,NULL);
	pthread_join(thd1,(void**)&val1);
	pthread_join(thd2,(void**)&val2);

	printf("val1:%d....val2:%d
",val1,val2);
	//pthread_mutex_destroy(&lock);
	return 0;
}

実行結果:
windows2 start:5 window1 start 5 sale finish:4 windows2 start:4 sale ticket finish:3 window1 start 3 sale finish:2 windows2 start:2 sale ticket finish:1 window1 start 1 sale finish:0 sale ticket finish:-1 val1:0....val2:0