为什么MSVC产生恒定时使用警告C4127＆QUOT;而＆QUOT; - C [英] Why MSVC generates warning C4127 when constant is used in "while" - C

问题描述

有关code，

while(1)
{
   /* ..... */
}

MSVC生成下列警告。

MSVC generates the following warning.

warning C4127: conditional expression is constant

MSDN ，在警告页面提示使用为（;;）而不是，而（1）。我想知道有什么优势为（;;）所赐，为什么它警告说，在的不断使用，同时？

MSDN page for the warning suggests to use for(;;) instead of while(1). I am wondering what advantage for(;;) is giving and why it warns for the constant usage in while?

我应该使用GCC上什么标志得到同样的警告？

What flag should I use on GCC to get the same warning?

推荐答案

恒条件等都很往往不够简单的错误。试想一下：

Constant conditionals are often enough simply bugs. Consider this:

unsigned k; 
...
while (k>=0) 
{
 ...
}

状况 K＆GT; = 0 才有意义，如果K是一个符号整数，而不是符号。一个不小心忘记了开发商当k被宣布无符号和他/她会使用它，如果它能够作为一个负数。编译器将尝试是有益的，提醒你这件事，而（1）落在编译器同样的问题类。 为（;;）是preferable，因为它明确地意味着永远`循环

The condition k>=0 would make sense if k was a signed int, but not for unsigned. A careless developer forgets that k was declared unsigned and he/she would use it as if it was usable as a negative number. The compiler tries to be helpful and warn you about this and while(1) falls for the compiler into the same problem class. for(;;) is preferable because it unambiguously means `loop forever

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