C++头文件＜bits/stdc++.h＞详解

前言

最近学了几节c++编程课，发现老师经常在代码第一行敲上一句：

#include <bits/c++std.h>

后来知道它原来是所谓的 “万能头文件”。
今天，我就给大家讲解一下它的用法和优缺点。

基本用法

#include <bits/stdc++.h>
using namespace std;
int main() {
	//在此处写代码
}

内容

// C++ includes used for precompiling -*- C++ -*-
 
// Copyright (C) 2003-2013 Free Software Foundation, Inc.
//
// This file is part of the GNU ISO C++ Library.  This library is free
// software; you can redistribute it and/or modify it under the
// terms of the GNU General Public License as published by the
// Free Software Foundation; either version 3, or (at your option)
// any later version.
 
// This library is distributed in the hope that it will be useful,
// but WITHOUT ANY WARRANTY; without even the implied warranty of
// MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
// GNU General Public License for more details.
 
// Under Section 7 of GPL version 3, you are granted additional
// permissions described in the GCC Runtime Library Exception, version
// 3.1, as published by the Free Software Foundation.
 
// You should have received a copy of the GNU General Public License and
// a copy of the GCC Runtime Library Exception along with this program;
// see the files COPYING3 and COPYING.RUNTIME respectively.  If not, see
// <Licenses - GNU Project - Free Software Foundation>.
 
/** @file stdc++.h
 *  This is an implementation file for a precompiled header.
 */
 
// 17.4.1.2 Headers
 
// C
#ifndef _GLIBCXX_NO_ASSERT
#include <cassert>
#endif
#include <cctype>
#include <cerrno>
#include <cfloat>
#include <ciso646>
#include <climits>
#include <clocale>
#include <cmath>
#include <csetjmp>
#include <csignal>
#include <cstdarg>
#include <cstddef>
#include <cstdio>
#include <cstdlib>
#include <cstring>
#include <ctime>
 
#if __cplusplus >= 201103L
#include <ccomplex>
#include <cfenv>
#include <cinttypes>
#include <cstdalign>
#include <cstdbool>
#include <cstdint>
#include <ctgmath>
#include <cwchar>
#include <cwctype>
#endif
 
// C++
#include <algorithm>
#include <bitset>
#include <complex>
#include <deque>
#include <exception>
#include <fstream>
#include <functional>
#include <iomanip>
#include <ios>
#include <iosfwd>
#include <iostream>
#include <istream>
#include <iterator>
#include <limits>
#include <list>
#include <locale>
#include <map>
#include <memory>
#include <new>
#include <numeric>
#include <ostream>
#include <queue>
#include <set>
#include <sstream>
#include <stack>
#include <stdexcept>
#include <streambuf>
#include <string>
#include <typeinfo>
#include <utility>
#include <valarray>
#include <vector>
 
#if __cplusplus >= 201103L
#include <array>
#include <atomic>
#include <chrono>
#include <condition_variable>
#include <forward_list>
#include <future>
#include <initializer_list>
#include <mutex>
#include <random>
#include <ratio>
#include <regex>
#include <scoped_allocator>
#include <system_error>
#include <thread>
#include <tuple>
#include <typeindex>
#include <type_traits>
#include <unordered_map>
#include <unordered_set>
#endif

包含了一大堆头文件，省下了写那么多头文件的时间。在有时限的竞赛中，往往可以用到。

优点和缺点

说了那么多，那么它真的是所有C++程序员们梦寐以求的 “万能头文件”吗？

优点

1. 可以节省大量写和搜头文件的时间。
2. 非常简洁，只需要一行代码就够了。

缺点

1. 包含的头文件太多，编译起来很费时间。
2. 在一些老版本的编译软件里可能并没有该头文件。

---

适用环境

1. 一些新版本的编译器里。
2. 国外一些计算机编程竞赛中可以使用。