C语言 gcc预处理后可以输出C代码吗？
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Can gcc output C code after preprocessing?
提问by LGTrader
I'm using an open source library which seems to have lots of preprocessing directives to support many languages other than C. So that I can study what the library is doing I'd like to see the C code that I'm compiling after preprocessing, more like what I'd write.
我正在使用一个开源库，它似乎有很多预处理指令来支持除 C 之外的许多语言。这样我就可以研究库正在做什么我想看看我在预处理后编译的 C 代码，更像是我写的。
Can gcc (or any other tool commonly available in Linux) read this library but output C code that has the preprocessing converted to whatever and is also readable by a human?
gcc（或 Linux 中常用的任何其他工具）可以读取这个库，但输出 C 代码，该代码将预处理转换为任何内容并且也可以被人类读取吗？
回答by mipadi
Yes. Pass gcc the -Eoption. This will output preprocessed source code.
是的。通过 gcc-E选项。这将输出预处理的源代码。
回答by tpdi
cppis the preprocessor.
cpp是预处理器。
Run cpp filename.cto output the preprocessed code, or better, redirect it to a file with
cpp filename.c > filename.preprocessed.
运行cpp filename.c以输出预处理的代码，或者更好地将其重定向到带有
cpp filename.c > filename.preprocessed.
回答by Hyman Ritter
I'm using gcc as a preprocessor (for html files.) It does just what you want. It expands "#--" directives, then outputs a readable file. (NONE of the other C/HTML preprocessors I've tried do this- they concatenate lines, choke on special characters, etc.) Asuming you have gcc installed, the command line is:
我使用 gcc 作为预处理器（用于 html 文件）。它可以满足您的需求。它扩展“#--”指令，然后输出一个可读文件。（我尝试过的其他 C/HTML 预处理器都没有这样做 - 它们连接行，阻塞特殊字符等。）假设您安装了 gcc，命令行是：
gcc -E -x c -P -C -traditional-cpp code_before.cpp > code_after.cpp
gcc -E -xc -P -C -traditional-cpp code_before.cpp > code_after.cpp
(Doesn't have to be 'cpp'.) There's an excellent description of this usage at http://www.cs.tut.fi/~jkorpela/html/cpre.html.
（不必是'cpp'。）http://www.cs.tut.fi/~jkorpela/html/cpre.html 上有关于这种用法的精彩描述。
The "-traditional-cpp" preserves whitespace & tabs.
“-traditional-cpp”保留空格和制表符。
回答by Andrii Pyvovar
Run:
跑：
gcc -E <file>.c
or
或者
g++ -E <file>.cpp
回答by Pranav Kumar
Suppose we have a file as Message.cpp or a .c file
假设我们有一个 Message.cpp 或 .c 文件
Steps 1:Preprocessing (Argument -E )
步骤 1：预处理（参数 -E）
g++ -E .\Message.cpp > P1
g++ -E .\Message.cpp > P1
P1 file generated has expanded macros and header file contents and comments are stripped off.
生成的 P1 文件扩展了宏，头文件内容和注释被剥离。
Step 2:Translate Preprocessed file to assembly (Argument -S). This task is done by compiler
步骤 2：将预处理文件转换为程序集（参数 -S）。此任务由编译器完成
g++ -S .\Message.cpp
g++ -S .\Message.cpp
An assembler (ASM) is generated (Message.s). It has all the assembly code.
生成汇编程序 (ASM) (Message.s)。它有所有的汇编代码。
Step 3:Translate assembly code to Object code. Note: Message.s was generated in Step2. g++ -c .\Message.s
第 3 步：将汇编代码转换为目标代码。注意：Message.s 是在 Step2 中生成的。 g++ -c .\Message.s
An Object file with the name Message.o is generated. It is the binary form.
生成名为 Message.o 的对象文件。它是二进制形式。
Step 4:Linking the object file. This task is done by linker
第 4 步：链接目标文件。此任务由链接器完成
g++ .\Message.o -o MessageApp
g++ .\Message.o -o MessageApp
An exe file MessageApp.exe is generated here.
这里生成了一个exe文件MessageApp.exe。
#include <iostream>
using namespace std;
//This a sample program
int main()
{
cout << "Hello" << endl;
cout << PQR(P,K) ;
getchar();
return 0;
}
