为什么有人会使用#if 1 C预处理程序指令？ [英] Why would somebody use an #if 1 C preprocessor directive?

问题描述

我正在查看一些 C 源代码，但我听不懂以下部分

I am looking through some C source code and I don't understand the following part

#if 1

   typedef unsigned short PronId;
   typedef unsigned short LMId;
#  define LM_NGRAM_INT

#else

   typedef unsigned int LMId;
   typedef unsigned int PronId;
#  undef LM_NGRAM_INT

#endif

为什么有人会这样做 #if 1 ？

Why would someone do #if 1? Isn't it true that only the first block will ever be processed?

推荐答案

是。..仅第一个块会被处理吗？ ---直到有人将1更改为0。然后将编译另一个块。这是在测试不同算法时临时切入和切出代码块的便捷方法。

Yes.. Only the first block will be processed --- until someone changes the 1 to a 0. Then the other block will be compiled. This is a convenient way to temporary switch blocks of code in and out while testing different algorithms.

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