On Dec 25, 2008, at 3:54 AM, Oliver Hunt wrote:
On Dec 25, 2008, at 2:18 AM, Javed Rabbani wrote:
Oliver,
<"That call to VirtualAlloc is inside a PLATFORM(WIN_OS) guard --
you should not be hitting it on a non-windows platform">
You are absolutely right about that. The VirtualAlloc() should
never be hit on non-Windows platform. Let me clarify, I am not
hitting the VirtualAlloc call on a non-Windows platform. I was just
referring to the point that what can be a possible alternative to
VirtualAlloc on embedded platforms. Looking through the code, the
VirtualAlloc is enabled for WIN_OS only as expected. For other
platforms like SYMBIAN for example, the fastMalloc() is enabled
with a comment that "VirtualAlloc is not available on Symbian, so
hack with fastMalloc".
It's perfectly possible it's broken in symbian -- the last symbian
release was from more than two years ago.
A bit of digging showed that Simon Hausmann added the SYMBIAN
fastMalloc branch, which implies this was for WebKit/Qt which builds
with fastMalloc disabled. So that call to fastMalloc is actually
just a call to standard system malloc, which i would guess, just by
pure luck allocates adequately aligned memory.
What are specific memory requirements that VirtualAlloc() fulfills
and fastMalloc() does not? What can be the workaround for
VirtualAlloc() on embedded platforms?
Alignment -- VirtualAlloc, mmap, vm_map all produce page aligned
memory (which is at least 4k aligned), and the posix_memalign
version appears to actually over align memory (my following of the
code makes me thinks it's requesting 64k alignment :-/ )
All of the #if branches allocateBlock will guarantee 64k alignment,
which is what is required. That's with the exception of the
PLATFORM(SYMBIAN) branch, which appears to be incorrect. I would
expect it to lead to crashes as a result of incorrect garbage
collection.
Does anyone know if Symbian has an official way to get an aligned
chunk of memory?
Regards,
Maciej
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