在 C 中创建 2 个 pthread

Question

我正在尝试制作一个简单的程序，该程序可以使用两个单独的线程计算圆的面积和周长：第一个线程应该计算周长，第二个pthread应该计算面积。 但是当我尝试编译它时，我收到以下消息：

> test1.c: In function ‘main’: test1.c:32:35: warning: passing argument
> 3 of ‘pthread_create’ from incompatible pointer type
> [-Wincompatible-pointer-types]    32 |     pthread_create (&pt1 , NULL
> , area ,NULL);
>       |                                   ^~~~
>       |                                   |
>       |                                   float * (*)(void *) In file included from test1.c:3: /usr/include/pthread.h:200:15: note: expected
> ‘void * (*)(void *)’ but argument is of type ‘float * (*)(void *)’  
> 200 |       void *(*__start_routine) (void *),
>       |       ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~ test1.c:33:35: warning: passing argument 3 of ‘pthread_create’ from incompatible
> pointer type [-Wincompatible-pointer-types]    33 |     pthread_create
> (&pt2 , NULL , circumference ,NULL);
>       |                                   ^~~~~~~~~~~~~
>       |                                   |
>       |                                   float * (*)(void *) In file included from test1.c:3: /usr/include/pthread.h:200:15: note: expected
> ‘void * (*)(void *)’ but argument is of type ‘float * (*)(void *)’  
> 200 |       void *(*__start_routine) (void *),
>       |       ~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~

这是代码：

#include <unistd.h>
#include <stdio.h>
#include <pthread.h>
#include <stdlib.h>
float *area (void *param)
{
int rad;
float PI = 3.14, area;
printf("nEnter radius of circle: ");
scanf("%d", &rad);
area = PI * rad * rad;
printf("narea: %f ", area);
return 0 ;
}
float *circumference (void *param)
{
int rad;
float PI = 3.14, cir;
printf("nEnter radius of circle: ");
scanf("%d", &rad);
cir = 2 * PI * rad;
printf("nCircumference : %f n", cir);
return 0;
}
int main ()
{
pthread_t pt1 ;
pthread_t pt2 ;
pthread_create (&pt1 , NULL , area ,NULL);
pthread_create (&pt2 , NULL , circumference ,NULL);
pthread_join (pt1 , NULL);
pthread_join (pt2 , NULL);
return 0;
}

Answer 1

将float替换为void

void *area (void *param)
void *circumference (void *param)