pthread 学习系列 case1-- 共享进程数据 VS 进程
1 #include <stdio.h> 2 #include <unistd.h> 3 #include <stdlib.h> 4 #include <pthread.h> 5 6 7 void *thread_foo_func(void *); 8 void *thread_bar_func(void *); 9 10 11 int global = 4; 12 13 14 int main(){ 15 int local = 8; 16 int foo, bar; 17 pthread_t fthread, bthread; 18 foo = pthread_create(&fthread, NULL, thread_foo_func, (void *)&local); 19 bar = pthread_create(&bthread, NULL, thread_bar_func, (void *)&local); 20 if (foo != 0 || bar != 0){ 21 printf("thread creation failed.\n"); 22 return -1; 23 } 24 25 26 foo = pthread_join(fthread, NULL); 27 bar = pthread_join(bthread, NULL); 28 if (foo != 0 || bar != 0){ 29 printf("thread join failed.\n"); 30 return -2; 31 } 32 33 34 printf("In thread main"); 35 printf("address of global %d: %x\n", global, &global); 36 printf("address of main local %d: %x\n", local, &local); 37 38 return 0; 39 } 40 41 42 void *thread_foo_func(void *arg){ 43 int foo_local = 16; 44 global ++; 45 *(int *)arg = 10; 46 printf("In thread foo_func"); 47 printf("address of global %d: %x\n", global, &global); 48 printf("address of main local %d: %x\n", *(int *)arg, arg); 49 printf("address of foo local: %x\n", &foo_local); 50 printf("\n"); 51 } 52 53 54 void *thread_bar_func(void *arg){ 55 int bar_local = 32; 56 global ++; 57 *(int *)arg = 20; 58 printf("In thread bar_func"); 59 printf("address of global %d: %x\n", global, &global); 60 printf("address of main local %d: %x\n", *(int *)arg, arg); 61 printf("address of bar local: %x\n", &bar_local); 62 printf("\n"); 63 }
打印输出结果
In thread foo_funcaddress of global 5: 8049a48 address of main local 10: bfc567b8 address of foo local: b7f553c4 In thread bar_funcaddress of global 6: 8049a48 address of main local 20: bfc567b8 address of bar local: b75543c4 In thread mainaddress of global 6: 8049a48 address of main local 20: bfc567b8
可见：
1 global 在线程中可见，而且共享，
2 main中的loca通过指针传给了进程，进程可以改变
3 两个线程中的私有变量是不同的，是线程私有的。
这和fork出的进程就完全不同
1 int global = 6; 2 3 int main(int argc,char** argv) 4 { 5 int var=10; 6 int pid=fork(); 7 if(pid==-1){ 8 printf("error!"); 9 } 10 else if(pid==0){ 11 global++; 12 var++; 13 printf("This is the child process!\n"); 14 } 15 else{ 16 printf("This is the parent process! child processid=%d\n",pid); 17 } 18 printf("%d, %d, %d \n", getpid(), global, var); 19 20 return 1; 21 }
打印结果：
This is the child process! 10769, 7, 11 This is the parent process! child processid=10769 10768, 6, 10
可见，调用fork，会有两次返回，一次是父进程、一次是子进程，因为子进程是父进程的副本，所以它拥有父进程数据空间、栈和堆的副本，它们并没有共享这些存储空间，它们只共享正文段。
