mac vscode 设置万能头文件的方法

1.首先找到include所在的文件夹。
clang++ -E -x c++ - -v < /dev/null
通过这条命令，找到如下目录：
/usr/local/include
/Library/Developer/CommandLineTools/usr/bin/../include/c++/v1
/Library/Developer/CommandLineTools/usr/lib/clang/12.0.0/include
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/usr/include
/Library/Developer/CommandLineTools/usr/include
/Library/Developer/CommandLineTools/SDKs/MacOSX10.15.sdk/System/Library/Frameworks (framework directory)

逐个进去，在第二个里发现了各种头文件。于是在该文件夹下建立子文件夹bits，然后在命令行模式下通过vi 新建一个stdc++.h文件，
将以下内容拷贝进去：

// C++ includes used for precompiling -*- C++ -*-// Copyright (C) 2003-2014 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
// <http://www.gnu.org/licenses/>./** @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 <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

保存以后，重新打开vscode，输入include<bits/stdc++.h>,可以通过编译了，大功告成！！

task.json:
{"tasks": [{"type": "cppbuild","label": "C/C++: clang++ 生成活动文件","command": "/usr/bin/clang++","args": ["-fcolor-diagnostics","-fansi-escape-codes","-g","${file}","-o","${fileDirname}/${fileBasenameNoExtension}"],"options": {"cwd": "${fileDirname}"},"problemMatcher": ["$gcc"],"group": "build","detail": "调试器生成的任务。"}],"version": "2.0.0"
}launch.json:
{"version": "0.2.0","configurations": [{"name": "C/C++: clang++ 生成和调试活动文件","type": "cppdbg","request": "launch","program": "${fileDirname}/${fileBasenameNoExtension}","args": [],"stopAtEntry": false,"cwd": "${fileDirname}","environment": [],"externalConsole": true,"MIMode": "lldb","preLaunchTask": "C/C++: clang++ 生成活动文件"},{"name": "(lldb) 启动","type": "cppdbg","request": "launch","program": "输入程序名称，例如 ${workspaceFolder}/a.out","args": [],"stopAtEntry": false,"cwd": "${fileDirname}","environment": [],"externalConsole": false,"MIMode": "lldb"}]
}c_cpp_properties.json:{"configurations": [{"name": "Mac","includePath": ["${workspaceFolder}/**","/usr/local/include","/usr/bin/"],"defines": [],"macFrameworkPath": ["/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/System/Library/Frameworks"],"cStandard": "c17","cppStandard": "c++17","intelliSenseMode": "macos-clang-x64"}],"version": 4
}