什么是找到一个类型的sizeof没有编译和执行code中的最简单的方法？ [英] What is the easiest way to find the sizeof a type without compiling and executing code?

问题描述

我写了一个bash脚本来确定海湾合作委员会的数据类型（如 ./ sizeof的INT双 的大小输出各自的大小 INT 和双击）通过包装每个参数在以下 p（）宏，然后编译和运行code。

I wrote a bash script to determine the size of gcc's datatypes (e.g. ./sizeof int double outputs the respective sizes of int and double) by wrapping each of its arguments in the following P() macro and then compiling and running the code.

#define P(x) printf("sizeof(" #x ") = %u\n", (unsigned int)sizeof(x))

问题是，这是相对缓慢的（需要整整一秒！），尤其是联步骤（因为有 -c 或编译-S 花费几乎没有时间，所以没有运行输出二进制）。一秒是不是真的由本身慢，但如果我使用其他脚本这个脚本，它会积少成多。

The problem is that this is relative slow (it takes a whole second!), especially the linking step (since compiling with -c or -S takes virtually no time, and so does running the outputted binary). One second is not really that slow by itself, but if I were to use this script in other scripts, it would add up.

有没有办法找到一个更快，更迂回的方式是什么尺寸 GCC 的数据类型使用？

Is there a faster, less roundabout way to find out what sizes gcc uses for datatypes?

推荐答案

可以实现只能使用GCC的preprocessor标准类型的功能。对于标准的类型有predefined宏：

You can achieve the functionality for standard types using the GCC's preprocessor only. For standard types there are predefined macros:

__SIZEOF_INT__
__SIZEOF_LONG__
__SIZEOF_LONG_LONG__
__SIZEOF_SHORT__
__SIZEOF_POINTER__
__SIZEOF_FLOAT__
__SIZEOF_DOUBLE__
__SIZEOF_LONG_DOUBLE__
__SIZEOF_SIZE_T__
__SIZEOF_WCHAR_T__
__SIZEOF_WINT_T__
__SIZEOF_PTRDIFF_T__

因此​​，通过使用code这样的：

So, by using code like the following:

#define TYPE_TO_CHECK __SIZEOF_INT__
#define VAL_TO_STRING(x) #x
#define V_TO_S(x) VAL_TO_STRING(x)
#pragma message V_TO_S(TYPE_TO_CHECK)
#error "terminate"

您将能够获得 __ __ SIZEOF_INT 从preprocessor本身的价值，甚至没有开始编译。在你的脚本，你可以定义 TYPE_TO_CHECK （用 -D ），以任何你需要并将其传递给GCC。当然，你会得到一些垃圾输出，但我相信你可以面对这一切。

you will be able to get the value of __SIZEOF_INT__ from the preprocessor itself without even starting the compilation. In your script you can define the TYPE_TO_CHECK (with -D) to whatever you need and pass it to gcc. Of course you will get some junk output, but I believe you can deal with that.

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