[ECOS] Malloc debug upsets alignment

[Dave Lawrence <dlawrence at ad-holdings dot co dot uk>]

Hi

If CYGDBG_MEMALLOC_MALLOC_DEBUG_GUARDS is set then an 8 byte offset is
added to the start of the buffer.  Therefore if
CYGNUM_MEMALLOC_ALLOCATOR_DLMALLOC_ALIGNMENT is > 3 the returned pointer
is guaranteed to not be aligned the way you expect it.

eg if the alignment specified is 6, one expects that (ptr % 64 == 0)
whereas the actual truth is that ((ptr - 8) % 64 == 0). ["ptr" being the
return value of malloc, in this context]

Having an unexpected alignment can, amongst other things, reduce the
performance of DMA engines and defeat your cache coherency strategy.

I would like to fix this but don't have time at the moment - switching
the debug guards off is an acceptable work around for me.

If / when I get a fix I'll post again -- if / when somebody else fixes
this I would appreciate a post.  Thanks!


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