将空指针提供给snprintf时的预期行为 [英] Expected behaviour when null pointer given to snprintf

问题描述

此代码段的预期行为是什么?

What is the expected behaviour for this code snippet?

char * aNullPointer = 0;
snprintf (res, 128, "Testing %s null pointer",aNullPointer);

请注意，我正在故意使它取消引用空指针aNullPointer.

Note that I am deliberately trying to get it to de-reference my null pointer aNullPointer.

行为1)res指向字符串测试(空)空指针"

Behaviour 1) res points to a string "Testing (null) null pointer"

行为2)段故障

根据我的平台，我似乎有不同的行为.有些snprintf实现执行健全性检查，而其他的则没有.

It seems I get differing behaviours depending on my platform. Some snprintf implementations perform a sanity check, whereas others do not.

最常见的行为是什么?

推荐答案

这是未定义的行为-没什么可期待的.某些实现会检查NULL并将其替换为"nil"或"null"的事实只是一个很好的事实，您根本不能依赖它.

It's undefined behavior - there's nothing to expect. The fact that some implementations check for NULL and replace it with "nil" or "null" is just a nicety, you can't rely on it at all.

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