伯爵用C preprocessor ​​2 code地点之间的线 [英] Count lines between two code locations in C preprocessor

问题描述

我想用C preprocessor来，计算两个code地点之间线路的数量。其基本思路是这样的：

I want to use the C preprocessor to count the amount of lines between two code locations. The basic idea is something like this:

#define START __LINE__
static char* string_list[] = {
    "some string",
    "another string",
    ...
    "last string"
};
#define END __LINE__
#if END - START > 42
    #error Too many entries
#endif

当然，这并不在这种情况下，因为工作开始和 END 仅仅是<$的重定义C $ C> __ __ LINE 宏。结果
我被玩弄的＃和 ## 运营商了一点，但我不能得到preprocessor评估开始和结束preprocessor运行时。

Of course this doesn't work because in this case START and END are merely redefinitions of the __LINE__ macro.
I was playing around a bit with the # and ## operators, but I could not get the preprocessor to evaluate START and END while the preprocessor is running.

我的问题是：这是可能在所有

My question is: is this possible at all?

检查运行期间，阵列的大小是不是一种选择。结果，
感谢提前任何提示或想法！

Checking the size of the array during runtime is not an option.
Thanks for any hints or ideas in advance!

推荐答案

您不应该使用这些宏用于此目的：如果你的地方引入一个额外的行code会变得完全不可维护。而如果有太多的几行？

You shouldn't use those macros for that purpose: the code will become completely unmaintainable if you introduce an extra line somewhere. And what if there are too few lines?

代替宏，使用静态断言：

Instead of macros, use a static assert:

static_assert(sizeof(string_list) / sizeof(*string_list) == SOME_CONSTANT,
               "Wrong number of entries in string list.");

如果你不使用它C11有static_assert的支持，你可以写这样的自信心，比如像这样的：

If you aren't using C11 which has support for static_assert, you can write such an assert yourself, for example like this:

#define COMPILE_TIME_ASSERT(expr) {typedef uint8_t COMP_TIME_ASSERT[(expr) ? 1 : 0];}

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