因为你没有显式地用struct stat而是直接用stat来定义结构体吧，毕竟stat函数和结构体都是一个名字。参考下面代码，编译会报错 $ cat a.cpp #include <stdio.h> struct foo { int i = 1; }; void foo(struct foo& x) { printf("%d\n", x.i); } int main() { foo x; foo(x); return 0; } $ g++ a.cpp -std=c++11 a.cpp: In function ‘int main()’: a.cpp:10:9: error: expected ‘;’ before ‘x’ foo x; ^ a.cpp:11:9: error: ‘x’ was not declared in this scope foo(x);