[ros-kernel] "My Computer" crash

[Mark Tempel]

Quoting Ge van Geldorp <ge at gse.nl>:

> When double-clicking on "My Computer" in VMware, Explorer would often
> crash, shutting down the system. I finally tracked it down to
> HeapAlloc() not always returning 8-byte aligned blocks (sometimes it
> would return blocks at xxxxxxx4 or xxxxxxxC). This causes
> Local/GlobalAlloc to misbehave. Someone before me already tried to fix
> it:

That was me.

>   phandle = RtlAllocateHeap(GetProcessHeap(), 0,
> sizeof(GLOBAL_HANDLE));
>   /* This little hack is to make sure that we get a pointer with 8-byte
>   ** alignment.
>   ** Fixme: When we are sure all allocations are 8-byte aligned,
>   ** we can remove this hack.
>   */
>   if (ISPOINTER(INTERN_TO_HANDLE(phandle)))
>   {
>       hack_fix = RtlAllocateHeap(GetProcessHeap(), 0,
> sizeof(GLOBAL_HANDLE));
>       RtlFreeHeap(GetProcessHeap(), 0, phandle);
>       phandle = hack_fix;
>   }
> 
> Unfortunately, the 2nd call to RtlAllocateHeap() was not guaranteed to
> return an 8-byte aligned block either. The end result was that
> GlobalAlloc returned what looked like a pointer while in reality it was
> a handle. Via a series of 4 memory overwrites this finally caused the
> crash. A small debugging nightmare I might add.

Crap. Sorry about that.  I should have spun on the allocate heap till I got an 8 
byte aligned block, but I like your fix better.


> Normally, I wouldn't bother y'all with this. However, I fixed it by
> adjusting some structures in reactos/lib/ntdll/rtl/heap.c and making a
> change to one of these low-level memory allocation routines while we're
> in a freeze period makes me feel slightly uneasy. OTOH, the problem in
> my opinion was seriously enough to need a fix ASAP.

This is extremly important.  It should be included.

one question: Did you remove the kludge code in GlobalAlloc ?

--mark