将指针字符参数传递给线程中的函数 [英] passing pointer char argument to function in thread

问题描述

当我执行这段代码时，我收到了一个细分错误（核心笨拙）。

  #include< ; pthread.h> 
 #include< stdio.h> 
 
 void function（char * oz）{
 
 char * y; 
 y =（char *）oz; 
 ** y =asd; 
 
 
返回NULL; 
} 
 
 int main（）{
 char * oz =oz\\\
; 
 
 pthread_t thread1; 
 
 if（pthread_create（& thread1，NULL，function，（void *）oz））{
 fprintf（stderr，Error creating thread \\\
）; 
返回1; 
 
 
 if（pthread_join（thread1，NULL））{
 fprintf（stderr，Error joining thread \\\
）; 
返回2; 
} 
 printf（％s，oz）; 
返回0; 
 
 
 $ / code $ / pre 
 
解决方案
需要决定，如何管理内存：是由调用者分配的内存，还是在线程函数内部。
 
 
 
如果内存由调用者分配，那么线程函数看起来像： 
 
 
  void * function（void * arg）
 {
 char * p = arg; 
 strcpy（p，abc）; // p指向由线程创建者分配的内存区域
返回NULL; 
} 
  
用法： 
 
 
  char数据[10] =oz; //分配10个字节并用'oz'初始化它们
 ... 
 pthread_create（& thread1，NULL，function，data）; 
  
如果内存是在线程函数内部分配的，那么您需要传递指针指针： 
  void * function（void * arg）
 {
 char ** p =（char ** ）精氨酸; 
 * p = strdup（abc）; //相当于malloc + strcpy 
返回NULL; 
} 
  
用法： 
 
 
  char * data =oz; //数据可以指向只读区域
 ... 
 pthread_create（& thread1，NULL，function，& data）; //传递指向变量
 ... 
的指针free（data）; //不需要数据 - 空闲内存 -  
  
 
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\n";

    pthread_t thread1;

    if(pthread_create(&thread1,NULL,function,(void *)oz)){
        fprintf(stderr, "Error creating thread\n");
        return 1;
    }

    if(pthread_join(thread1,NULL)){
        fprintf(stderr, "Error joining thread\n");
        return 2;
    }
    printf("%s",oz);
    return 0;

}

解决方案
First you need to decide, how you want to manage the memory: is the memory allocated by caller, or inside the thread function.


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;
}
Usage:
char data[10] = "oz"; // allocate 10 bytes and initialize them with 'oz'
...
pthread_create(&thread1,NULL,function,data);
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;
}
Usage:
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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