如何在 C++ 项目中使用 C 源文件？
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How to use C source files in a C++ project?
提问by Al2O3
In a C++ project, including .h files of C source files will cause many errors because of different standards between C and C++.
How to use C source files in a C++ project (or in main.cpp)?
在C++项目中，包含C源文件的.h文件会因为C和C++的标准不同而导致很多错误。
如何在 C++ 项目（或 main.cpp）中使用 C 源文件？
回答by Jonathan Leffler
For the maximum reliability:
为了获得最大的可靠性：
- Compile the C source with a C compiler.
- Compile the C++ source with a C++ compiler
- Preferably, write the main() function in C++.
- Link the program with a C++ compiler.
- 使用 C 编译器编译 C 源代码。
- 使用 C++ 编译器编译 C++ 源代码
- 最好用 C++ 编写 main() 函数。
- 将程序与 C++ 编译器链接。
Make sure that the C headers are either themselves aware of C++ or that the C++ code includes the C headers inside an extern "C" { ... }block.
确保 C 头文件本身知道 C++，或者 C++ 代码在extern "C" { ... }块内包含 C 头文件。
Either (C header file cheader.h):
任一（C 头文件cheader.h）：
#ifndef CHEADER_H_INCLUDED
#define CHEADER_H_INCLUDED
#ifdef __cplusplus
extern "C" {
#endif
...main contents of header...
#ifdef __cplusplus
}
#endif
#endif /* CHEADER_H_INCLUDED */
or (C++ source code):
或（C++ 源代码）：
extern "C" {
#include "cheader.h"
}
Modern C style is very close to the common subset of the C and C++ languages. However, arbitrary C code is not C++ code for any of a very large number of reasons, and simply calling the C source files C++ source files (by changing the extension, or simply by compiling with the C++ compiler) is not guaranteed to be successful. In general, it is easier to compile C as C and C++ as C++ and then link the resulting object files with the C++ compiler (to ensure the correct support libraries are invoked).
现代 C 风格非常接近 C 和 C++ 语言的公共子集。但是，任意 C 代码由于多种原因都不是 C++ 代码，并且仅调用 C 源文件 C++ 源文件（通过更改扩展名，或仅通过使用 C++ 编译器进行编译）并不能保证成功. 通常，将 C 编译为 C，将 C++ 编译为 C++，然后将生成的目标文件与 C++ 编译器链接（以确保调用正确的支持库）更容易。
However, if the MSVC compiler is saying that programs using MFC have to be written solely in C++ (MFC requires C++ compilation (use a .cpp suffix)is the reported error), then you may have no choice but to ensure that your C code is compilable as C++ code. That means you'll have to cast the return values from malloc()et al; you have to worry about other places where you do not use a cast to convert a void *into some other pointer type; you have to worry about sizeof('a') == 4in C and sizeof('a') == 1in C++; you have to ensure that every function is declared before it is used; you have to ensure your C code does not use any C++ keywords (typename, classin particular; also inlinesometimes — but the complete list is quite large).
但是，如果 MSVC 编译器说使用 MFC 的程序必须仅用 C++ 编写（MFC 需要 C++ 编译（使用 .cpp 后缀）是报告的错误），那么您可能别无选择，只能确保您的 C 代码可编译为 C++ 代码。这意味着您必须转换来自malloc()et al的返回值；您必须担心其他不使用强制转换将 a 转换void *为其他指针类型的地方；你必须sizeof('a') == 4在 C 和sizeof('a') == 1C++ 中担心；您必须确保每个函数在使用之前都已声明；你必须确保你的C代码，不使用任何C ++的关键字（typename，class尤其;也inline有时候-但完整列表是相当大的）。
In some circles, you'd have to worry about the use of features in C99 that are not in C++2003 or C++2011, such as flexible array members, designated initializers, compound literals, variable-length arrays, and so on. However, if the C code is for MSVC, then that probably isn't going to be a problem; those features are not supported by the MSVC C compiler (it only supports C89, not C99).
在某些圈子中，您不得不担心 C99 中 C++2003 或 C++2011 中没有的特性的使用，例如灵活的数组成员、指定的初始值设定项、复合字面量、变长数组等等在。但是，如果 C 代码用于 MSVC，那么这可能不会成为问题；MSVC C 编译器不支持这些功能（它只支持 C89，不支持 C99）。
FWIW: I have a script to hunt down C++ keywords. It contains the following comment:
FWIW：我有一个脚本来寻找 C++ 关键字。它包含以下评论：
# http://en.cppreference.com/w/cpp/keywords
# plus JL annotations
# and C (<iso646.h>)
# and_eq C (<iso646.h>)
# alignas (C++11 feature)
# alignof (C++11 feature)
# asm C (core)
# auto(1) C (core)
# bitand C (<iso646.h>)
# bitor C (<iso646.h>)
# bool C99 (<stdbool.h>)
# break C (core)
# case C (core)
# catch
# char C (core)
# char16_t (C++11 feature)
# char32_t (C++11 feature)
# class
# compl C (<iso646.h>)
# const C (core)
# constexpr (C++11 feature)
# const_cast
# continue C (core)
# decltype (C++11 feature)
# default(1) C (core)
# delete(1)
# double C (core)
# dynamic_cast
# else C (core)
# enum C (core)
# explicit
# export
# extern C (core)
# false C99 (<stdbool.h>)
# float C (core)
# for C (core)
# friend
# goto C (core)
# if C (core)
# inline C (core)
# int C (core)
# long C (core)
# mutable
# namespace
# new
# noexcept (C++11 feature)
# not C (<iso646.h>)
# not_eq C (<iso646.h>)
# nullptr (C++11 feature)
# operator
# or C (<iso646.h>)
# or_eq C (<iso646.h>)
# private
# protected
# public
# register C (core)
# reinterpret_cast
# return C (core)
# short C (core)
# signed C (core)
# sizeof C (core)
# static C (core)
# static_assert (C++11 feature)
# static_cast
# struct C (core)
# switch C (core)
# template
# this
# thread_local (C++11 feature)
# throw
# true C99 (<stdbool.h>)
# try
# typedef C (core)
# typeid
# typename
# union C (core)
# unsigned C (core)
# using(1)
# virtual
# void C (core)
# volatile C (core)
# wchar_t C (core)
# while C (core)
# xor C (<iso646.h>)
# xor_eq C (<iso646.h>)
The (1)suffixes is a footnote at CPP Reference:
该(1)后缀是CPP参考脚注：
(1)— meaning changed in C++11
(1)— 含义在 C++11 中发生了变化
回答by Syntactic Fructose
C++ preaches "backwards compatibility" to C source, so an option would be to copy the C source onto a .cpp file and build. Now C++ is not COMPLETELYbackwards compatible, so you might need to change some things around in the C source, but generally it should build with minimal errors. Just make sure you include the C library's that the .c uses(considering your compiler supports C also)
C++ 宣扬对 C 源代码的“向后兼容性”，因此一个选项是将 C 源代码复制到 .cpp 文件并构建。现在 C++不完全向后兼容，因此您可能需要更改 C 源代码中的一些内容，但通常它应该以最小的错误构建。只需确保包含 .c 使用的 C 库（考虑到您的编译器也支持 C）
#include <stdio.h>
#include <string.h>
//so on
回答by Salchi13
if you are just using the source code and not some precompiled libraries, in most of the cases you could just rename the .c file to a .cpp file
如果您只是使用源代码而不是一些预编译库，在大多数情况下，您只需将 .c 文件重命名为 .cpp 文件
