#2917: alloca and allocaArray do not respect alignment
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Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal | Milestone: _|_
Component: Compiler (FFI) | Version: 6.12.3
Resolution: | Keywords:
Testcase: | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown |
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Comment(by Lemming):
For a wrapper around 'malloc' we could waste less memory, if we would
require that 'free' has a Storable constraint and requires that its
pointer type matches the one of the corresponding 'malloc'. With the size
and alignment information, 'malloc' and 'free' could decide whether to pad
at all. Even if they pad, they can save memory by putting the pointer to
full allocated block ''after'' the block of aligned data. E.g. compare the
layout, where 'p' is a byte of the pointer to the full allocated block,
'a' is a byte of 16-byte aligned data, and '*' is allocated but unused
(=wasted) padding byte.
{{{
0 0 1 2 2
0 C 0 0 F
************ppppaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaa
0 1 2 2
0 0 0 3
aaaaaaaaaaaaaaaaaaaaaaaaaaaaaaaapppp
}}}
--
Ticket URL: <http://hackage.haskell.org/trac/ghc/ticket/2917#comment:25>
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The Glasgow Haskell Compiler
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