text: #include <stdio.h>
  // T: 全局变量
  
  int f(void);
  
  int gAll = 12;
  
  int main(int argc, char* argv[]) {
    printf("in %s gAll = %d\n", __func__, gAll);
    f();
    printf("again in %s gAll = %d\n", __func__, gAll);
  
    return 0;
  }
  
  int f(void) {
    // int gAll = 1; // 本地变量隐藏全局变量
  
    printf("in %s gAll = %d\n", __func__, gAll);
    gAll += 2;
    printf("again in %s gAll = %d\n", __func__, gAll);
  
    return gAll;
  }
  