What is a bus error?

“总线错误”消息的含义是什么，它与段错误有什么不同？

---

Bus errors are rare nowadays on x86 and occur when your processor cannot even attempt the memory access requested, typically:

using a processor instruction with an address that does not satisfy its alignment requirements.

Segmentation faults occur when accessing memory which does not belong to your process, they are very common and are typically the result of:

using a pointer to something that was deallocated.

using an uninitialized hence bogus pointer.

using a null pointer.

overflowing a buffer.

PS: To be more precise this is not manipulating the pointer itself that will cause issues, it's accessing the memory it points to (dereferencing).

---

A segfault is accessing memory that you're not allowed to access. It's read-only, you don't have permission, etc...

A bus error is trying to access memory that can't possibly be there. You've used an address that's meaningless to the system, or the wrong kind of address for that operation.

---

I believe the kernel raises SIGBUS when an application exhibits data misalignment on the data bus. I think that since most[?] modern compilers for most processors pad / align the data for the programmers, the alignment troubles of yore (at least) mitigated, and hence one does not see SIGBUS too often these days (AFAIK).

From: Here

链接地址: http://www.djcxy.com/p/35370.html

上一篇: 我如何在Xcode 4中设置NSZombieEnabled？

下一篇: 什么是巴士错误？