任何理由使用运行时断言而不是编译时断言？ [英] Any reason to use a run-time assert instead of compile-time assert?

问题描述

在查看Visual C ++代码库时，我发现了一个很奇怪的事情。在编译时可以评估条件的情况下使用运行时断言（如果条件被违反则检查条件并抛出异常）：

  assert（sizeof（SomeType）== sizeof（SomeOtherType））; 
  

清楚地，编译器将评估条件并替换实际上是

  assert（true）; 
  

不执行任何操作，或

  assert（false）; 
 

每当控件通过该行时都会抛出异常。

IMO应该使用编译时断言，原因如下：

$ b

看起来像编译时断言是唯一正确的事情。有没有可能的理由喜欢这里的运行时断言？

解决方案

没有理由喜欢运行时断言。你应该更喜欢编译时错误超过运行时错误，所以没有一个理由，给定两者之间的选择，选择一个运行时断言。





但是，如果一个静态断言不是一个选项（不知道静态断言的概念，不知道如何使一个可用，或者知道如何使一个可用，但没有时间





对于C ++ 0x，内置的 static_assert 功能应该终止所有原因使用运行时断言其中编译时断言将工作。




While reviewing Visual C++ codebase I found a following strange thing. A run-time assert (which is check the condition and throw an exception if the condition is violated) was used in a case when the condition could be evaluated at compile time:

assert( sizeof( SomeType ) == sizeof( SomeOtherType ) );

clearly the compiler will evaluate the condition and replace the code that will effectively be either

assert( true );

which does nothing or

assert( false );

which throws an exception every time control passes through that line.

IMO a compile-time assert should have be used instead for the following reasons:

• it would expose the condition violation earlier - at compile time - and
• it would let cleaner (thus faster and smaller) machine code be emitted

Looks like a compile-time assert is the only right thing. Is there any possible reason to prefer a run-time assert here?

解决方案

There's no reason to prefer a run-time assert here. You should prefer compile-time errors over run-time errors so there's never a reason, given the option between the two, to choose a run-time assert.

However, if a static assert isn't an option (doesn't know the concept of a static assert, doesn't know how to make one and doesn't have one available, or knows how to make one but doesn't have the time to), a run-time assert is the next best thing.

With C++0x, the built-in static_assert feature should end all reason to use a run-time assert where a compile-time assert would work.

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