Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- 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| -+-- Changes (by dterei): * cc: dterei (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:26 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- 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| -+-- Changes (by Lemming): * cc: g...@… (added) Comment: Replying to [comment:22 simonmar]: Taking it off the milestone. The only remaining things to do are `malloc` and `mallocBytes`: these use C malloc, which satisfies the minimum alignment requirement for any native datatype, so there shouldn't be a problem in most cases. On my machine the 'malloc' manpage says, that 'malloc' aligns correctly for any variable, but apparently it does not. Maybe the statement was true before the 16-byte vectors of SSE. We are not the first ones who use SSE, how could the problem be missed by the kernel developers? So I'm uncertain whether the behaviour of 'malloc' is intended or not and thus whether we should fix Haskell libraries or the Linux kernel. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:24 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment
-+--
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|
-+--
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
0 1 2 2
0 0 0 3
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:25
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment
-+--
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|
-+--
Changes (by guest):
* cc: danield...@… (added)
* version: 6.10.1 = 6.12.3
Comment:
I wasted several hours to find out that my LLVM related Haskell code is
also affected by this problem (I found it in mallocArray). I already found
out, that LLVM's malloc intrinsic is broken in this way, but I expected
Haskell's malloc is correct in this respect. My malloc(C) manpage says:
For calloc() and malloc(), return a pointer to the allocated
memory, which is suitably aligned for any kind of variable. But sometimes
it returns pointers that are not divisible by 16, only by 8. Thus it
seems, that malloc or its manpage is buggy.
My solution is to allocate a memory chunk that is 16+sizeof(ptr) bytes
larger. Then I choose a start address within that chunk that is divisible
by 16 and leaves space for a pointer to the full allocated chunk, that I
store just before that 16-byte-aligned address.
{{{
#include stdlib.h
void *aligned_malloc(size_t size) {
const int ptrsize = sizeof(void *);
void *ptr = malloc(size+16+ptrsize);
if (ptr) {
void **alignedptr = (void **)((size_t)(ptr+16+ptrsize) (-16));
*(alignedptr-1) = ptr;
return alignedptr;
} else {
return NULL;
}
};
void aligned_free(void *alignedptr) {
void **sptr = (void **) alignedptr;
void *ptr = *(sptr - 1);
free(ptr);
};
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:23
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment
-+--
Reporter: guest | Owner:
Type: bug | Status: new
Priority: high| Milestone: 6.14.1
Component: Compiler (FFI) |Version: 6.10.1
Resolution: | Keywords:
Testcase: | Blockedby:
Difficulty: Unknown | Os: Unknown/Multiple
Blocking: | Architecture: Unknown/Multiple
Failure: None/Unknown|
-+--
Comment(by simonmar):
Also fixed `allocaArray`:
{{{
Thu Aug 12 03:55:24 PDT 2010 Simon Marlow marlo...@gmail.com
* export allocaBytesAligned; make allocaArray use the correct alignment
(#2917)
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:21
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler
___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest | Owner: Type: bug | Status: new Priority: normal | Milestone: _|_ Component: Compiler (FFI) |Version: 6.10.1 Resolution: | Keywords: Testcase: | Blockedby: Difficulty: Unknown | Os: Unknown/Multiple Blocking: | Architecture: Unknown/Multiple Failure: None/Unknown| -+-- Changes (by simonmar): * priority: high = normal * milestone: 6.14.1 = _|_ Comment: Taking it off the milestone. The only remaining things to do are `malloc` and `mallocBytes`: these use C malloc, which satisfies the minimum alignment requirement for any native datatype, so there shouldn't be a problem in most cases. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:22 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest | Owner: Type: bug | Status: new Priority: high| Milestone: 6.14.1 Component: Compiler (FFI) |Version: 6.10.1 Resolution: | Keywords: Difficulty: Unknown | Os: Unknown/Multiple Testcase: | Architecture: Unknown/Multiple Failure: None/Unknown| -+-- Changes (by kfrdbs): * cc: kfr...@… (added) -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:21 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler ___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: Type: bug | Status: new Priority: high |Milestone: 6.12 branch Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Comment (by igloo): See also #1605. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:19 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: Type: bug | Status: new Priority: high |Milestone: 6.12 branch Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by igloo): * status: reopened = new * owner: igloo = -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:18 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: igloo Type: bug | Status: reopened Priority: high |Milestone: 6.12 branch Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by igloo): * type: merge = bug -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:17 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: igloo Type: merge | Status: reopened Priority: high |Milestone: 6.12 branch Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by igloo): * status: closed = reopened * resolution: fixed = * milestone: 6.10.2 = 6.12 branch -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:16 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: simonmar Type: bug | Status: new Priority: high |Milestone: 6.10.2 Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by igloo): * owner: igloo = simonmar -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:13 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: igloo Type: bug | Status: new Priority: high |Milestone: 6.10.2 Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Comment (by igloo): See also #2983. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:12 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment -+-- Reporter: guest |Owner: igloo Type: bug | Status: new Priority: high |Milestone: 6.10.2 Component: Compiler (FFI)| Version: 6.10.1 Severity: normal| Resolution: Keywords:| Difficulty: Unknown Testcase:| Os: Unknown/Multiple Architecture: Unknown/Multiple | -+-- Changes (by igloo): * type: merge = bug Comment: That patch was buggy (segfaults on 32-bit platforms, amongst other problems), so I've rolled it back. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:11 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: simonmar Type: bug | Status: new Priority: high|Milestone: 6.10.2 Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Changes (by simonmar): * owner: = simonmar Comment: I'll do as Lennart suggests and bump the default alignment to 16 bytes. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:9 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment
---+
Reporter: guest |Owner:
Type: bug | Status: new
Priority: high|Milestone: 6.10.2
Component: Compiler (FFI) | Version: 6.10.1
Severity: normal | Resolution:
Keywords: | Difficulty: Unknown
Testcase: | Os: Unknown/Multiple
Architecture: x86 |
---+
Comment (by igloo):
I'm a little nervous about rushing this in, particularly as it changes
(adds to) some APIs, and I'm not sure exactly what the behaviour should
be.
You say
{{{
mallocAlignment :: Int
mallocAlignment = 16
allocaAlignment :: Int
allocaAlignment = 8
}}}
but my manpage says
{{{
GNU libc malloc() always returns 8-byte aligned memory addresses
}}}
Where did 16 come from? It also seems strange to me that `allocaAlignment`
should be different to `mallocAlignment`.
According to my OS X manpages, OS X doesn't have `posix_memalign` or
`memalign`, although it does have `valloc` (The allocated memory is
aligned on a page boundary.). However, for all the allocation functions
on OS X, The allocated memory is aligned such that it can be used for any
data type, including AltiVec- and SSE-related types.. So if we're told
the alignment is 32, and we get memory 16-byte aligned, should we fail?
It's not clear to me.
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:7
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: high|Milestone: 6.10.2 Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Comment (by guest): The mallocAlignment is the alignment returned by C malloc(), the allocaAlignment is the alignment for ghc's heap based allocation. I should have spelled that out. Those two things should not be numbers, of course, but determined by the configure script. yes, OS X malloc() works fine, but ghc's internal allocation fails since it allocates on 8 byte boundary. I don't want to rush this in either. But the bug makes large parts of the FFI library unusable with LLVM, so I'd like some fix. How about a band aid that changes ghc's internal alloca to 16 byte boundary? That will make things work, and we have a chance to test my patch further. -- Lennart -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:8 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: high|Milestone: 6.10.2 Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Changes (by igloo): * priority: normal = high * milestone: = 6.10.2 -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:6 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: normal |Milestone: Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Comment (by simonmar): Yes, good point. The `allocaBytes` version is fine, btw (except that it should avoid wasting memory when alignement = 8). `posix_memalign()` is the only way I know to allocate aligned memory from the OS. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:5 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: normal |Milestone: Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Comment (by guest): Trying to fix my patch to not waste memory I realized that the patch is broken. It takes a pointer from some internal malloc and adjusts it for alignment. This will not work when that pointer is later given to free. I'm not sure how to fix this. It seems we need to have the low level allocator return a pointer that is properly aligned, otherwise giving the block back to the low level free will never work. In short, I don't know how to fix this. Note that this is a real problem. Using SSE instructions on the x86 requires the vectors to be properly aligned, otherwise you get a fault. So I can't use any of the allocators for Storable in Foreign (nor Data.Array.Storable) when allocating vectors. A hack would be to have the allocator return everything 16 byte aligned, but that really is a hack. The longer term solution must take alignment into account. -- Lennart -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:3 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: normal |Milestone: Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Comment (by guest): I'm working on a new patch that I think will work, except it relies on posix_memalign() which seems to be a rare beast. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:4 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment ---+ Reporter: guest |Owner: Type: bug | Status: new Priority: normal |Milestone: Component: Compiler (FFI) | Version: 6.10.1 Severity: normal | Resolution: Keywords: | Difficulty: Unknown Testcase: | Os: Unknown/Multiple Architecture: x86 | ---+ Changes (by simonmar): * difficulty: = Unknown Comment: Thanks for the patch. As it stands, this will waste memory when the required alignment is = 8 bytes, since `allocaBytes` and `mallocBytes` both always return 8-byte aligned memory. Could you modify the patch to take that into account? -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:2 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
Re: [GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment --+- Reporter: guest | Owner: Type: bug | Status: new Priority: normal| Milestone: Component: Compiler (FFI)|Version: 6.10.1 Severity: normal| Resolution: Keywords:| Testcase: Os: Unknown/Multiple | Architecture: x86 --+- Comment (by guest): I've added a patch to use the alignment when allocating. -- Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917#comment:1 GHC http://www.haskell.org/ghc/ The Glasgow Haskell Compiler___ Glasgow-haskell-bugs mailing list Glasgow-haskell-bugs@haskell.org http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
[GHC] #2917: alloca and allocaArray do not respect alignment
#2917: alloca and allocaArray do not respect alignment
-+--
Reporter: guest | Owner:
Type: bug | Status: new
Priority: normal| Component: Compiler (FFI)
Version: 6.10.1| Severity: normal
Keywords:| Testcase:
Os: Unknown/Multiple | Architecture: x86
-+--
When allocating memory with alloca or allocaArray the alignment of the
Storable is not respected, alignment seems to be on 8 byte boundary.
malloc and mallocArray seem to have the same problem. And because of this
functions like withArray etc also break the alignment restriction of the
array element.
Run this and look at the pointer.
{{{
import Foreign.Ptr
import Foreign.Storable
import Foreign.Marshal.Array
import Foreign.Marshal
data Foo = Foo
instance Storable Foo where
sizeOf _ = 8
alignment _ = 256
main =
allocaArray 5 $ \ p - do
let _ = p :: Ptr Foo
print p
q - mallocArray 5
let _ = q :: Ptr Foo
print q
}}}
--
Ticket URL: http://hackage.haskell.org/trac/ghc/ticket/2917
GHC http://www.haskell.org/ghc/
The Glasgow Haskell Compiler___
Glasgow-haskell-bugs mailing list
Glasgow-haskell-bugs@haskell.org
http://www.haskell.org/mailman/listinfo/glasgow-haskell-bugs
