为什么使用g ++而不是gcc来编译* .cc文件？ [英] why use g++ instead of gcc to compile *.cc files?

问题描述

我编译了一个使用g ++而不是gcc的库。首先我认为源代码是用C ++编写的，但我后来发现，在* .cc文件中没有任何C ++代码。

I compiled a library which use the g++ instead gcc. First I thought the source code was written in C++ but I found out later that there was not any C++ code in the *.cc files.

为了确认这一点，我用gcc替换了原来makefile中的g ++。我还是得到了正确的程序。

To confirm this, I replaced the g++ in the original makefile with gcc. And I still got the correct program.

任何人都可以解释这一点？这不是我第一次遇到这种情况。

Anyone can explain this? It was not the first time I met such a situation.

推荐答案

这取决于你在makefile中改变了什么。 gcc / g ++ 实际上只是一个前端驱动程序，它调用实际的编译器和/

It depends on what exactly you changed in the makefile. gcc / g++ is really just a front-end driver program which invokes the actual compiler and / or linker based on the options you give it.

如果您调用编译器 gcc ：

• 它会根据文件扩展名（ .c ）将编译为C或C ++ .cc / .cpp ）;


• 作为C，即它不会拉入C ++库，除非你专门添加额外的参数这样做。

• it will compile as C or C++ based on the file extension (.c, or .cc / .cpp);
• it will link as C, i.e. it will not pull in C++ libraries unless you specifically add additional arguments to do so.

调用编译器 g ++ ：

• 无论文件扩展名是 .c 还是 .cc / .cpp ;


• 会将链接为C ++，即自动拉入标准C ++库。

• it will compile as C++ regardless of whether or not the file extension is .c or .cc / .cpp;
• it will link as C++, i.e. automatically pull in the standard C++ libraries.

（请参阅 GCC文档的相关位）。

这是一个简单的程序，或者不是它已经编译为C或C ++。

Here's a simple program which detects whether or not it has been compiled as C or C++.

（它使用一个字符常量的大小为 int 或C ++中的 char 。 sizeof（char）根据定义为1; sizeof（int）通常会更大 - 除非你使用一个含有> = 16位字节的模糊平台，你可能不是这样。）

(It makes use of the fact that a character constant has the size of an int in C, or a char in C++. sizeof(char) is 1 by definition; sizeof(int) will generally be larger - unless you're using an obscure platform with >= 16-bit bytes, which you're probably not.)

我调用它 test.c 并将其复制为 test.cc 以及：

I've called it test.c and copied it as test.cc as well:

$ cat test.c
#include <stdio.h>

int main(void)
{
  printf("I was compiled as %s!\n", sizeof('a') == 1 ? "C++" : "C");
  return 0;
}
$ cp test.c test.cc
$

使用 gcc 和 test.cc 编译和链接 test.c $ c>与 g ++ 可按预期工作：

Compiling and linking test.c with gcc, and test.cc with g++, works as expected:

$ gcc -o test test.c
$ ./test
I was compiled as C!
$ g++ -o test test.cc
$ ./test
I was compiled as C++!
$ 

编译和链接 test.cc 与 gcc 不工作：它编译代码为C ++，因为文件以 .cc 但在链接阶段失败：

Compiling and linking test.cc with gcc doesn't work: it compiles the code as C++ because the file ends in .cc, but fails at the link stage:

$ gcc -o test test.cc
/tmp/ccyb1he5.o:(.eh_frame+0x11): undefined reference to `__gxx_personality_v0'
collect2: ld returned 1 exit status
$ 

我们可以通过单独编译 gcc 并链接到 g ++ 拉入正确的库）：

which we can prove by separately compiling with gcc, and linking with g++ (to pull in the right libraries):

$ gcc -c test.cc
$ g++ -o test test.o
$ ./test
I was compiled as C++!
$

... gcc 将代码编译为C ++而不是C，因为它有一个 .cc 文件扩展名。

...gcc has compiled the code as C++ rather than C, because it had a .cc file extension.

code> g ++ 不会将 .c 编译为纯C：

Whereas g++ does not compile .c files as plain C:

$ g++ -o test test.c 
$ ./test
I was compiled as C++!
$ 

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