Linux pthread_create 不起作用。传递参数 3 警告
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pthread_create not working. passing argument 3 warning
提问by randomizertech
I am trying to create a thread and from what I remember this should be the right way to do it:
我正在尝试创建一个线程，据我所知，这应该是正确的方法：
#include <pthread.h>
#include <stdio.h>
#include <stdlib.h>
#define NUM_THREADS 5
int SharedVariable =0;
void SimpleThread(int which)
{
int num,val;
for(num=0; num<20; num++){
if(random() > RAND_MAX / 2)
usleep(10);
val = SharedVariable;
printf("*** thread %d sees value %d\n", which, val);
SharedVariable = val+1;
}
val=SharedVariable;
printf("Thread %d sees final value %d\n", which, val);
}
int main (int argc, char *argv[])
{
pthread_t threads[NUM_THREADS];
int rc;
long t;
for(t=0; t< NUM_THREADS; t++){
printf("In main: creating thread %ld\n", t);
rc = pthread_create(&threads[t], NULL, SimpleThread, (void* )t);
if (rc){
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
}
/* Last thing that main() should do */
pthread_exit(NULL);
}
And the error that I'm getting is this one:
我得到的错误是这个：
test.c: In function ‘main': test.c:28: warning: passing argument 3 of ‘pthread_create' from incompatible pointer type /usr/include/pthread.h:227: note: expected ‘void * (*)(void *)' but argument is of type ‘void (*)(int)'
test.c：在函数'main'中：test.c:28：警告：从不兼容的指针类型/usr/include/pthread.h:227传递'pthread_create'的参数3：注意：预期'void * (* )( void *)' 但参数的类型是 'void (*)(int)'
I cannot change the SimpleThread function so changing the type of the parameter is not an option even though I already tried and it didn't work either.
我无法更改 SimpleThread 函数，因此更改参数的类型不是一个选项，即使我已经尝试过并且它也不起作用。
What am I doing wrong?
我究竟做错了什么？
采纳答案by dasblinkenlight
SimpleThreadshould be declared as
SimpleThread应该声明为
void* SimpleThread(void *args) {
}
When you pass parameters to your thread, it is best to define a structfor them, pass a pointer to that structas void*, and cast back to the right type inside the function.
将参数传递给线程时，最好struct为它们定义 a ，将指向该参数的指针传递给structas void*，然后转换回函数内部的正确类型。
回答by Sean Bright
Here's a compiling and "working" version of your program, although I have to admit to not knowing exactly what it's doing. For the critics in the audience, I apologize in advance for the pthread_joinloop at the end.
这是您程序的编译和“工作”版本，尽管我不得不承认不知道它在做什么。对于观众中的批评者，我提前为pthread_join结尾的循环道歉。
#include <stdio.h>
#include <stdlib.h>
#include <pthread.h>
#define NUM_THREADS 5
struct my_thread_info {
long which;
};
int SharedVariable = 0;
void *SimpleThread(void *data)
{
int num, val;
struct my_thread_info *info = data;
for (num = 0; num < 20; num++) {
if (random() > RAND_MAX / 2)
usleep(10);
val = SharedVariable;
printf("*** thread %ld sees value %d\n", info->which, val);
SharedVariable = val + 1;
}
val = SharedVariable;
printf("Thread %ld sees final value %d\n", info->which, val);
free(info);
return NULL;
}
int main(int argc, char *argv[])
{
pthread_t threads[NUM_THREADS];
int rc;
long t;
struct my_thread_info *info;
for (t = 0; t < NUM_THREADS; t++) {
printf("In main: creating thread %ld\n", t);
info = malloc(sizeof(struct my_thread_info));
info->which = t;
rc = pthread_create(&threads[t], NULL, SimpleThread, info);
if (rc) {
printf("ERROR; return code from pthread_create() is %d\n", rc);
exit(-1);
}
}
for (t = 0; t < NUM_THREADS; t++) {
pthread_join(threads[t], NULL);
}
}
