将指针 char 参数传递给线程中的函数 [英] passing pointer char argument to function in thread
本文介绍了将指针 char 参数传递给线程中的函数的处理方法,对大家解决问题具有一定的参考价值,需要的朋友们下面随着小编来一起学习吧!
问题描述
当我执行此代码时,我收到分段错误(核心愚蠢)".
When I execute this code, I'm receiving a "segmentation error (core dumbed)".
#include <pthread.h>
#include <stdio.h>
void function(char *oz){
char *y;
y = (char*)oz;
**y="asd";
return NULL;
}
int main(){
char *oz="oz
";
pthread_t thread1;
if(pthread_create(&thread1,NULL,function,(void *)oz)){
fprintf(stderr, "Error creating thread
");
return 1;
}
if(pthread_join(thread1,NULL)){
fprintf(stderr, "Error joining thread
");
return 2;
}
printf("%s",oz);
return 0;
}
推荐答案
首先你需要决定,你想如何管理内存:是调用者分配的内存,还是线程函数内部.
First you need to decide, how you want to manage the memory: is the memory allocated by caller, or inside the thread function.
如果内存是由调用者分配的,那么线程函数将如下所示:
If the memory is allocated by caller, then the thread function will look like:
void *function(void *arg)
{
char *p = arg;
strcpy(p, "abc"); // p points to memory area allocated by thread creator
return NULL;
}
用法:
char data[10] = "oz"; // allocate 10 bytes and initialize them with 'oz'
...
pthread_create(&thread1,NULL,function,data);
如果内存是在线程函数内部分配的,那么你需要传递指针到指针:
If the memory is allocated inside the thread function, then you need to pass pointer-to-pointer:
void *function(void *arg)
{
char **p = (char**)arg;
*p = strdup("abc"); // equivalent of malloc + strcpy
return NULL;
}
用法:
char *data = "oz"; // data can point even to read-only area
...
pthread_create(&thread1,NULL,function,&data); // pass pointer to variable
...
free(data); // after data is not needed - free memory-
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