我经常听到有人说,在编译C和c++程序时,我应该“总是启用编译器警告”。为什么这是必要的?我怎么做呢?

有时我也听到我应该“把警告当作错误”。我应该吗?我怎么做呢?


当前回答

将警告视为错误只是自律的一种方式:您正在编译一个程序来测试那个闪亮的新功能,但是在您修复那些草率的部分之前,您无法测试。werror提供了其他信息。它只是非常明确地设定了优先级:

在修复现有代码中的问题之前,不要添加新代码

重要的是心态,而不是工具。编译器诊断输出是一种工具。MISRA C(嵌入式C)是另一个工具。使用哪一种并不重要,但可以说编译器警告是最简单的工具(只需设置一个标志),而且信噪比非常高。所以没有理由不使用它。

No tool is infallible. If you write const float pi = 3.14;, most tools won't tell you that you defined π with a bad precision which may lead to problems down the road. Most tools won't raise an eyebrow on if(tmp < 42), even if it's commonly known that giving variables meaningless names and using magic numbers is a way to disaster in big projects. You have to understand that any "quick test" code you write is just that: a test, and you have to get it right before you move on to other tasks, while you still see its shortcomings. If you leave that code as is, debugging it after you spend two months adding new features will be significantly harder.

一旦你进入了正确的心态,使用-Werror就没有意义了。将警告作为警告将允许您做出明智的决定,是否仍然有意义运行您即将开始的调试会话,还是中止它并首先修复警告。

其他回答

这是C的一个具体答案,以及为什么这对C来说比其他任何东西都重要。

#include <stdio.h>

int main()
{
   FILE *fp = "some string";
}

此代码编译时带有警告。地球上几乎所有其他语言(除了汇编语言)中存在的和应该存在的错误都是C语言中的警告。C语言中的警告几乎都是伪装的错误。警告应该被修正,而不是被压制。

对于GCC,我们执行GCC -Wall -Werror。

这也是微软一些不安全API警告引起高度不满的原因。大多数编写C语言的人已经学会了将警告视为错误的艰难方法,而这些东西出现的不是同一种东西,需要不可移植的修复。

众所周知,就hll而言,C是一种相当低级的语言。虽然c++看起来是一种比C高级得多的语言,但它仍然具有C的一些特征。其中一个特点就是这些语言是由程序员设计的,为程序员设计的——特别是那些知道自己在做什么的程序员。

(对于这个答案的其余部分,我将专注于C。我要说的大部分内容也适用于c++,尽管可能没有那么强烈。尽管Bjarne Stroustrup有一句名言:“C很容易搬起石头砸自己的脚;c++让它变得更难,但当你这样做的时候,它会把你的整条腿都炸掉。”)

如果你知道你在做什么——真的知道你在做什么——有时候你可能不得不“打破规则”。但大多数时候,我们大多数人都会同意,善意的规则让我们所有人都远离麻烦,一直肆意违反这些规则是一个坏主意。

But in C and C++, there are surprisingly large numbers of things you can do that are "bad ideas", but which aren't formally "against the rules". Sometimes they're a bad idea some of the time (but might be defensible other times); sometimes they're a bad idea virtually all of the time. But the tradition has always been not to warn about these things — because, again, the assumption is that programmers know what they are doing, they wouldn't be doing these things without a good reason, and they'd be annoyed by a bunch of unnecessary warnings.

当然,并不是所有的程序员都知道自己在做什么。特别是,每个C程序员(无论多么有经验)都要经历一个开始C程序员的阶段。即使是有经验的C程序员也会粗心大意,犯错误。

最后,经验表明,程序员不仅会犯错误,而且这些错误会产生真正的、严重的后果。如果你犯了一个错误,编译器没有警告你,而且程序没有立即崩溃,或者因为它而做一些明显的错误,这个错误可能潜伏在那里,隐藏,有时长达数年,直到它造成一个真正的大问题。

So it turns out that, most of the time, warnings are a good idea, after all. Even the experienced programmers have learned that (actually, it's "especially the experienced programmers have learned that"), on balance, the warnings tend to do more good than harm. For every time you did something wrong deliberately and the warning was a nuisance, there are probably at least ten times you did something wrong by accident and the warning saved you from further trouble. And most warnings can be disabled or worked around for those few times when you really want to do the "wrong" thing.

(这类“错误”的一个经典例子是if(A = b)的测试。大多数时候,这确实是一个错误,所以现在大多数编译器都会对此发出警告——有些甚至是默认的。但是如果你真的想把b赋值给a并测试结果,你可以通过输入if((a = b))来禁用警告。

The second question is, why would you want to ask the compiler to treat warnings as errors? I'd say it's because of human nature, specifically, the all-too-easy reaction of saying "Oh, that's just a warning, that's not so important, I'll clean that up later." But if you're a procrastinator (and I don't know about you, but I'm a world-class procrastinator) it's easy to put off the necessary cleanup for basically ever — and if you get into the habit of ignoring warnings, it gets easier and easier to miss an important warning message that's sitting there, unnoticed, in the midst of all the ones you're relentlessly ignoring.

因此,要求编译器将警告视为错误是你可以对自己玩的一个小技巧,以避免这个人类的弱点,迫使自己立即修复警告,否则你的程序将无法编译。

Personally, I'm not as insistent about treating warnings as errors — in fact, if I'm honest, I can say that I don't tend to enable that option in my "personal" programming. But you can be sure I've got that option enabled at work, where our style guide (which I wrote) mandates its use. And I would say — I suspect most professional programmers would say — that any shop that doesn't treat warnings as errors in C is behaving irresponsibly, is not adhering to commonly-accepted industry best practices.

你一定要启用编译器警告,因为一些编译器不擅长报告一些常见的编程错误,包括以下:

初始化变量会被遗忘 从一个被错过的函数返回一个值 printf和scanf族中的简单参数与格式字符串不匹配 函数的使用没有事先声明,尽管这只在C中发生

所以这些函数可以被检测和报告,只是通常不是默认情况;所以这个特性必须通过编译器选项显式地请求。

警告是等待发生的错误。 因此,您必须启用编译器警告,并整理代码以删除任何警告。

由于某些原因,c++中的编译器警告非常有用。

它可以告诉你,你可能在哪里犯了一个错误,这可能会影响你的操作的最终结果。例如,如果你没有初始化一个变量,或者如果你使用“=”而不是“==”(这只是例子) 它还允许向你展示你的代码不符合c++标准的地方。这很有用,因为如果代码符合实际标准,那么将很容易将代码移到其他平台。

一般来说,警告是非常有用的,可以告诉您代码中哪里有错误,这些错误可能会影响算法的结果,或者在用户使用您的程序时防止出现某些错误。