我们模拟一家唐杜里鸡肉自助餐厅，一位厨师和一位厨师 多个来宾，类似于单个生产者/多个消费者问题。我们 实现一个具有多个线程的程序，每个线程都拥有一个厨师或一个客人。 我们还应用了一个同步工具 - 信号量，它可以解决问题 使用多个线程同步公共资源。通过这个项目，我们将学习 如何创建多线程进程以及如何使用信号量同步线程。
#include <stdlib.h>
#include <stdio.h>
#include <pthread.h>
#include <semaphore.h>
struct threadInfo
{
int id;
};
/* input variables */
int nofCustomers=4,item,nofChicken=3;
pthread_attr_t attr; /*Set of thread attributes*/
pthread_t chef_t,customer_t[100];
/* the semaphores */
sem_t full, empty;
void *chef(void *param); /* the producer thread */
void *customer(void *param); /* the consumer thread */
void initializeData()
{
/* Create the full semaphore and initialize to 0 */
sem_init(&full, 0, 0);
/* Create the empty semaphore and initialize to BUFFER_SIZE */
sem_init(&empty, 0, nofChicken);
/* Get the default attributes */
pthread_attr_init(&attr);
}
PRODUCER
/* Producer Thread */
void *chef(void *param)
{
printf("Chef Starts Cooking\n");
while(1)
{
/* acquire the empty lock */
sem_wait(&empty);
if(insert_item())
{
fprintf(stderr, " Producer report error condition\n");
}
/* signal full */
sem_post(&full);
sleep(1);
}
}
消费者
/* Consumer Thread */
void *customer(void *param)
{
int toeat=1+rand()%4,ate=0,t=nofCustomers;
int *id=(int*)param;
printf("Guest %d arrives and wants to eat %d food\n", id, toeat);
while(1)
{
/* aquire the full lock */
sem_wait(&full);
if(remove_item())
{
fprintf(stderr, "Consumer report error condition\n");
}
else
{
ate++;
printf("Guest %d eats a tandoori chicken[%d/%d]\n", id,ate,toeat);
}
if(ate==toeat)
{
nofCustomers--;
printf("Guest %d finishes and exits\n",id);
}
if(nofCustomers==0)
{
printf("All guests finish eating and exit\n");
break ;
}
/* signal empty */
sem_post(&empty);
sleep(toeat);
}
}
iNC在关键部分
/* Cook food */
int insert_item()
{
/* When the item is not full,cook food
increment the item*/
if(item <= nofChicken)
{
item++;
printf("Chef cooks one tandoori chicken.[%d/%d]\n",item,nofChicken);
return 0;
}
else
{ /* Error the items are full */
return -1;
}
}
DEC在关键部分
/* Eat food */
int remove_item() {
/* When the items is/are cooked, eat the item
i.e.., decrement the item */
if(item > 0)
{
item--;
return 0;
}
else { /* Error no items */
return -1;
}
}
主要功能
int main()
{
/* Loop counter */
int i;
struct threadInfo *info;
//input (Havent written code for input includes nofChicken andnofCustomers
/* Initialize the app */
initializeData();
/* Create the producer thread */
pthread_create(&chef_t,&attr,chef,NULL);
/* Create the consumer threads */
for(i = 1; i <= nofCustomers; i++)
{
info->id=i;
pthread_create(&customer_t[i],&attr,customer,(void *)info);
}
return 0;
}
BOVE CODE中的分段错误
答案 0 :(得分：1)
首先，修复这些编译错误：
g++ -std=c++17 -fPIC -g -Wall -Wextra -Wwrite-strings -Wno-parentheses -Wpedantic -Warray-bounds -O2 -Weffc++ 39988874.cpp -o 39988874
39988874.cpp: In function ‘void* chef(void*)’:
39988874.cpp:43:25: error: ‘insert_item’ was not declared in this scope
if (insert_item()) {
^
39988874.cpp:48:16: error: ‘sleep’ was not declared in this scope
sleep(1);
^
39988874.cpp:36:18: warning: unused parameter ‘param’ [-Wunused-parameter]
void *chef(void *param)
^~~~~
39988874.cpp: In function ‘void* customer(void*)’:
39988874.cpp:58:68: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int*’ [-Wformat=]
printf("Guest %d arrives and wants to eat %d food\n", id, toeat);
^
39988874.cpp:63:25: error: ‘remove_item’ was not declared in this scope
if (remove_item()) {
^
39988874.cpp:67:77: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int*’ [-Wformat=]
printf("Guest %d eats a tandoori chicken[%d/%d]\n", id,ate,toeat);
^
39988874.cpp:71:54: warning: format ‘%d’ expects argument of type ‘int’, but argument 2 has type ‘int*’ [-Wformat=]
printf("Guest %d finishes and exits\n",id);
^
39988874.cpp:79:20: error: ‘sleep’ was not declared in this scope
sleep(toeat);
^
39988874.cpp:56:32: warning: unused variable ‘t’ [-Wunused-variable]
int toeat=1+rand()%4,ate=0,t=nofCustomers;
^
39988874.cpp:81:1: warning: no return statement in function returning non-void [-Wreturn-type]
}
^
<builtin>: recipe for target '39988874' failed
make: *** [39988874] Error 1
（提示：您#include <unistd.h>需要sleep();此外，您还需要int id = ((threadInfo*)param)->id）
修好了那些，你将被留下
39988874.cpp: In function ‘int main()’:
39988874.cpp:133:17: warning: ‘info’ may be used uninitialized in this function [-Wmaybe-uninitialized]
info->id=i;
~~~~~~~~^~
这显然是由
引起的struct threadInfo *info;
/* ... */
for (i = 1; i <= nofCustomers; i++) {
info->id=i;
}
有你的问题。您需要将info指向某个有效的存储空间。
答案 1 :(得分：-1)
在编译代码时使用-Wall并消除（或至少仔细观察）所有警告。