cpp和gcc -E之间的区别 [英] Difference between cpp and gcc -E

问题描述

我认为 cpp foo.c 和 gcc -E foo.c 都可以对源文件进行预处理

I thought that both cpp foo.c and gcc -E foo.c do preprocess the source file the same way, but I got their output to differ for the same file.

$ cat foo.c
#define VARIABLE 3
#define PASTER(x,y) x ## _ ## y
#define EVALUATOR(x,y)  PASTER(x,y)
#define NAME(fun) EVALUATOR(fun, VARIABLE)

extern void NAME(mine);

cpp 的结果：

$ cpp foo.c
# 1 "foo.c"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 329 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "foo.c" 2





extern void mine ## _ ## 3;

$

gcc -E 和 clang -E ：

$ gcc -E foo.c
# 1 "foo.c"
# 1 "<built-in>" 1
# 1 "<built-in>" 3
# 330 "<built-in>" 3
# 1 "<command line>" 1
# 1 "<built-in>" 2
# 1 "foo.c" 2





extern void mine_3;
$

为什么这些输出会有所不同，以及当我想要使用哪个输出时请参阅预处理的源代码？

Why do those outputs differ, and which one should I use when I want to see the preprocessed source ?

原始代码此处

推荐答案

两者之间的区别在于 gcc -E 将消除 -traditional-cpp 。如果包含该选项，则应该收到与 cpp 相同的结果。

The difference between the two is that gcc -E will eliminate -traditional-cpp. If you include the option then you should receive the same result as cpp.

↳ https://gcc.gnu.org/onlinedocs/cpp/Traditional-Mode.html

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