如何表示指向我的地址空间开头的指针？ [英] How do I represent a pointer to the beginning of my address space?

问题描述

让我们考虑一些奇怪的假设嵌入式系统，我需要产生和使用一个指针，指向或可能指向我的地址空间的第一个字节。也就是说，指针等于零。不是一个NULL指针，而是一个完全有效的零指针，它可能像任何其他指针一样被取消引用或递增或作为数组处理。我如何在将NULL指针视为特殊的语言，但没有一个真正的NULL类型？

解决方案

在一些罕见的旧机器上，整个具有不同于0的特殊值的NULL指针是可能的，但实际上，指向地址0的NULL / 0指针将具有值0，并且在大多数机器上真正指向地址0 。

这将是完全可解除引用的，如果有一些内存映射到这个区域，你可以在该地址上写。

我曾经在一个嵌入式平台上工作过。所以我习惯在地址0上放置一个调试器观察点，因为对这个区域的所有访问都是NULL指针解引用。以这种方式捕获一些错误^^

Let's consider some strange hypothetical embedded system where I need to produce and use a pointer that points to, or might point to, the first byte of my address space. That is, a pointer equal to zero. Not a NULL pointer, but a perfectly valid zero pointer, which might get dereferenced or incremented or treated as an array just like any other pointer. How would I do this in languages that treat a NULL pointer as special, but don't have a real NULL type?

解决方案

The whole "NULL pointer having a special value different than 0 treated special" is a possibility on some rare old machines, but in practice, your NULL/0 pointer pointing to adress 0 will have value 0 and really point to address 0 on most machines.

It will be perfectly dereferenceable, and you can write on that address if there is some memory mapped to this area.

I used to have that on an embedded platform I worked with. So I used to put a debugger watchpoint on address 0, since all accesses to this area were NULL-pointers dereferences. Caught some errors that way ^^

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