#include <stdlib.h>
#include <string.h>
#include <stdio.h>
#include <pthread.h>
void* th_func(){
        char c[100];
        printf("c=%p, tid=%d\n", c, pthread_self());
        return (void*)0;
}
void p(char* x[]){
        printf("pppp=%d\n", sizeof(x));
}
void c(int v, int d){
        if(d>3) return;
        v+=v*d;
        printf("v=%p\n", &v);
        c(v,d+1);
}
int main(){
        printf("int=%d, long=%d, long long=%d\n", sizeof(int), sizeof(long), sizeof(long long));
        int i;

        printf("Test in main:\n----------------------------------------\n");
        th_func();
        th_func();

        printf("Abort size of arr arr*\n----------------------------------------\n");
        short ss[]={1,23,4,5,55,5,6,7};
        char* xx[]={"sadl","da","22","dd","sd"};

        printf("short=%d,char*=%d\n----------------------------------------\n", sizeof(ss), sizeof(xx));
        p(xx);

        printf("String char action:\n----------------------------------------\n");
        char *str="123456789";
        if(str[1]>0)
                printf("%d > 0\n",str[1]);
        else
                printf("%d < 0\n",str[1]);


        char* x = "TO019";
        printf("mah num=%d\n", atoi(x+4));
        printf("----------------------------------------\n");
        printf("Function call itself:\n----------------------------------------\n");
        c(1,0);


        printf("Test in thread:\n----------------------------------------\n");
        for(i=0;i<5;i++){
                pthread_t tid;
                if(pthread_create(&tid, NULL, th_func, NULL)!=0)
                {
                        printf(" pthread_create failed\n");
                        exit(1);
                }
        }

        sleep(3);
return 0;}

 

結果：

int=4, long=8, long long=8
Test in main:
----------------------------------------
c=0x7ffc9df43fb0, tid=2116724480
c=0x7ffc9df43fb0, tid=2116724480
Abort size of arr arr*
----------------------------------------
short=16,char*=40
----------------------------------------
pppp=8
String char action:
----------------------------------------
50 > 0
mah num=9
----------------------------------------
Function call itself:
----------------------------------------
v=0x7ffc9df4401c
v=0x7ffc9df43ffc
v=0x7ffc9df43fdc
v=0x7ffc9df43fbc
Test in thread:
----------------------------------------
c=0x7f1a7c4a4e40, tid=2085246720
c=0x7f1a7baa3e40, tid=2074756864
c=0x7f1a7cea5e40, tid=2095736576
c=0x7f1a7d8a6e40, tid=2106226432
c=0x7f1a7e2a7e40, tid=2116716288
 

結論：

在同一個執行緒反覆呼叫一個函式，其區域性變數使用同一個記憶體空間；

在不同執行緒呼叫一個函式、或函式多次遞迴呼叫自己，其區域性變數使用不同記憶體空間；

因此，執行緒安全要解決的是全域性變數、靜態變數。