创建线程-传递参数 [英] create thread - passing arguments
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问题描述
我正在尝试创建多个线程,每个线程计算一个素数.我试图使用线程创建将第二个参数传递给函数.它不断抛出错误.
I am attempting on creating multiple threads that each thread calculates a prime. I am trying to pass a second argument to a function using thread create. It keeps throwing up errors.
void* compute_prime (void* arg, void* arg2)
{
这是我的带有创建线程的main(). & max_prime之后的& primeArray [i]给了我错误.
here is my main() with the create thread. &primeArray[i] after &max_prime is giving me the errors.
for(i=0; i< num_threads; i++)
{
primeArray[i]=0;
printf("creating threads: \n");
pthread_create(&primes[i],NULL, compute_prime, &max_prime, &primeArray[i]);
thread_number = i;
//pthread_create(&primes[i],NULL, compPrime, &max_prime);
}
/* join threads */
for(i=0; i< num_threads; i++)
{
pthread_join(primes[i], NULL);
//pthread_join(primes[i], (void*) &prime);
//pthread_join(primes[i],NULL);
//printf("\nThread %d produced: %d primes\n",i, prime);
printf("\nThread %d produced: %d primes\n",i, primeArray[i]);
sleep(1);
}
我得到的错误是:
myprime.c: In function âmainâ:
myprime.c:123: warning: passing argument 3 of âpthread_createâ from incompatible pointer type
/usr/include/pthread.h:227: note: expected âvoid * (*)(void *)â but argument is of type âvoid * (*)(void *, void *)â
myprime.c:123: error: too many arguments to function âpthread_createâ
如果我删除第二个参数,效果很好.
It works fine if i take out the second argument.
推荐答案
您只能将单个参数传递给在新线程中调用的函数.创建一个结构以容纳这两个值并发送该结构的地址.
You can only pass a single argument to the function that you are calling in the new thread. Create a struct to hold both of the values and send the address of the struct.
#include <pthread.h>
#include <stdlib.h>
typedef struct {
//Or whatever information that you need
int *max_prime;
int *ith_prime;
} compute_prime_struct;
void *compute_prime (void *args) {
compute_prime_struct *actual_args = args;
//...
free(actual_args);
return 0;
}
#define num_threads 10
int main() {
int max_prime = 0;
int primeArray[num_threads];
pthread_t primes[num_threads];
for (int i = 0; i < num_threads; ++i) {
compute_prime_struct *args = malloc(sizeof *args);
args->max_prime = &max_prime;
args->ith_prime = &primeArray[i];
if(pthread_create(&primes[i], NULL, compute_prime, args)) {
free(args);
//goto error_handler;
}
}
return 0;
}
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