[M3devel] platform-independent packing/alignment?

Mon Feb 1 09:19:06 CET 2010

For what it's worth...

I recall someone (Dragisa?) just complained that he was having problems
unpickling data structures...

I have never had much luck pickling and unpickling MUTEXes, using a few
(not very different) M3 compilers.  I just leave them out of my pickles.
It makes the pickles a lot more compatible across versions.  I'm not
talking recent CM3 versions here but a variety of old versions.
Implementors have seemed to modify MUTEX quite a bit.  What's the point
of pickling it anyhow?  If it's an active mutex the unpickling will
surely lead to garbage, if there are wait queues and things.. then you
wind up un/pickling Thread structures too.

     Mika

Tony Hosking writes:
>
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>That shouldn't affect things since the pickler picks apart the =
>structures and ships the individual primitives.  Right?
>
>On 1 Feb 2010, at 02:41, Jay K wrote:
>
>> Let's say I have:
>> =20
>> =20
>> TYPE FOO =3D RECORD a: LONGFLOAT; b: UINT32; END;
>> TYPE FOOA =3D ARRAY [0..1] OF FOO;
>> =20
>> =20
>> And I have a platform with max_align =3D 32 and a platform with =
>max_align =3D 64.
>> One platform will make FOOA be 24 bytes, the other 32.
>>   One platform will pad out FOO to be align the 8 byte LONGFLOAT, one =
>won't.
>> Can that pickle be read/written by the two platforms?
>> And how does the code know/detect the difference?
>> That is, if a platform changed from max_align =3D 32 to 64, would the =
>pickle code work just
>> as well on the "same" platform as on the "different" platforms?
>> =20
>> =20
>> I very recently changed NT386 max_align from 32 to 64, and I believe
>> the remaining active platforms with max_align =3D 32 should also be =
>64.
>> It would "only" affect pickles with LONGINT or LONGFLOAT, as well
>> as "lining up" such structs with C.
>> =20
>> =20
>> Such alignment shold make us not need the extra "unaligned double" =
>switch
>> on most platforms (some mystery still on some platforms) as well as
>> perhaps be needed for some atomic operations, esp. maybe on
>> LONGINT on 32bit x86.
>> =20
>> =20
>>  - Jay
>>=20
>> =20
>> > From: dragisha at m3w.org
>> > To: rodney_bates at lcwb.coop
>> > Date: Sun, 31 Jan 2010 22:14:47 +0100
>> > CC: m3devel at elegosoft.com
>> > Subject: Re: [M3devel] platform-independent packing/alignment?
>> >=20
>> > I've not changed my code, that is for sure.... But now I am not sure
>> > some parent type (esp MUTEX here an there) was not changed... I'll =
>take
>> > a look on this again sometime soon and report my findings.
>> >=20
>> > Thanks for clues.
>> >=20
>> > On Sun, 2010-01-31 at 14:00 -0600, Rodney M. Bates wrote:
>> > >=20
>> > > Dragi=C5=A1a Duri=C4=87 wrote:
>> > > > I've asked this before, but didn't catch answer:
>> > > >=20
>> > > > On Sun, 2010-01-31 at 12:21 +0000, Jay K wrote:
>> > > >> I suggest we can probably get by with platform-independent
>> > > >> packing/alignment settings.
>> > > >=20
>> > > > Some time ago I've used pickles (CM3) to save some data... My =
>program
>> > > > does not read that pickle anymore....=20
>> > >=20
>> > > And you are certain your program that tries to read still contains
>> > > exact structurally equivalent types to all the types in the =
>pickle?
>> > >=20
>> > > >=20
>> > > > Someone remembers moment when this incompatible changes were =
>made?=20
>> > --=20
>> > Dragi=C5=A1a Duri=C4=87 <dragisha at m3w.org>
>> >=20
>
>
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><html><head><base href=3D"x-msg://140/"></head><body style=3D"word-wrap: =
>break-word; -webkit-nbsp-mode: space; -webkit-line-break: =
>after-white-space; ">That shouldn't affect things since the pickler =
>picks apart the structures and ships the individual primitives. =
> Right?<div>
><br><div><div>On 1 Feb 2010, at 02:41, Jay K wrote:</div><br =
>class=3D"Apple-interchange-newline"><blockquote type=3D"cite"><span =
>class=3D"Apple-style-span" style=3D"border-collapse: separate; =
>font-family: Helvetica; font-size: medium; font-style: normal; =
>font-variant: normal; font-weight: normal; letter-spacing: normal; =
>line-height: normal; orphans: 2; text-indent: 0px; text-transform: none; =
>white-space: normal; widows: 2; word-spacing: 0px; =
>-webkit-border-horizontal-spacing: 0px; -webkit-border-vertical-spacing: =
>0px; -webkit-text-decorations-in-effect: none; -webkit-text-size-adjust: =
>auto; -webkit-text-stroke-width: 0px; "><div class=3D"hmmessage" =
>style=3D"font-size: 10pt; font-family: Verdana; ">Let's say I =
>have:<br> <br> <br>TYPE FOO =3D RECORD a: LONGFLOAT; b: =
>UINT32; END;<br>TYPE FOOA =3D ARRAY [0..1] OF =
>FOO;<br> <br> <br>And I have a platform with max_align =
>=3D 32 and a platform with max_align =3D 64.<br>One platform will =
>make FOOA be 24 bytes, the other 32.<br>  One platform will =
>pad out FOO to be align the 8 byte LONGFLOAT, one won't.<br>Can that =
>pickle be read/written by the two platforms?<br>And how does the code =
>know/detect the difference?<br>That is, if a platform changed from =
>max_align =3D 32 to 64, would the pickle code work just<br>as =
>well on the "same" platform as on the "different" =
>platforms?<br> <br> <br>I very recently changed NT386 =
>max_align from 32 to 64, and I believe<br>the remaining active platforms =
>with max_align =3D 32 should also be 64.<br>It would "only" affect =
>pickles with LONGINT or LONGFLOAT, as well<br>as "lining up" such =
>structs with C.<br> <br> <br>Such alignment shold make us not =
>need the extra "unaligned double" switch<br>on most platforms (some =
>mystery still on some platforms) as well as<br>perhaps be needed for =
>some atomic operations, esp. maybe on<br>LONGINT on 32bit =
>x86.<br> <br> <br> - Jay<br><br> <br>> From:<span =
>class=3D"Apple-converted-space"> </span><a =
>href=3D"mailto:dragisha at m3w.org">dragisha at m3w.org</a><br>> To:<span =
>class=3D"Apple-converted-space"> </span><a =
>href=3D"mailto:rodney_bates at lcwb.coop">rodney_bates at lcwb.coop</a><br>> =
>Date: Sun, 31 Jan 2010 22:14:47 +0100<br>> CC:<span =
>class=3D"Apple-converted-space"> </span><a =
>href=3D"mailto:m3devel at elegosoft.com">m3devel at elegosoft.com</a><br>> =
>Subject: Re: [M3devel] platform-independent =
>packing/alignment?<br>><span =
>class=3D"Apple-converted-space"> </span><br>> I've not changed =
>my code, that is for sure.... But now I am not sure<br>> some parent =
>type (esp MUTEX here an there) was not changed... I'll take<br>> a =
>look on this again sometime soon and report my findings.<br>><span =
>class=3D"Apple-converted-space"> </span><br>> Thanks for =
>clues.<br>><span class=3D"Apple-converted-space"> </span><br>> =
>On Sun, 2010-01-31 at 14:00 -0600, Rodney M. Bates wrote:<br>> =
>><span class=3D"Apple-converted-space"> </span><br>> > =
>Dragi=C5=A1a Duri=C4=87 wrote:<br>> > > I've asked this before, =
>but didn't catch answer:<br>> > ><span =
>class=3D"Apple-converted-space"> </span><br>> > > On Sun, =
>2010-01-31 at 12:21 +0000, Jay K wrote:<br>> > >> I suggest =
>we can probably get by with platform-independent<br>> > >> =
>packing/alignment settings.<br>> > ><span =
>class=3D"Apple-converted-space"> </span><br>> > > Some =
>time ago I've used pickles (CM3) to save some data... My program<br>> =
>> > does not read that pickle anymore....<span =
>class=3D"Apple-converted-space"> </span><br>> ><span =
>class=3D"Apple-converted-space"> </span><br>> > And you are =
>certain your program that tries to read still contains<br>> > =
>exact structurally equivalent types to all the types in the =
>pickle?<br>> ><span =
>class=3D"Apple-converted-space"> </span><br>> > ><span =
>class=3D"Apple-converted-space"> </span><br>> > > Someone =
>remembers moment when this incompatible changes were made?<span =
>class=3D"Apple-converted-space"> </span><br>> --<span =
>class=3D"Apple-converted-space"> </span><br>> Dragi=C5=A1a =
>Duri=C4=87 <<a =
>href=3D"mailto:dragisha at m3w.org">dragisha at m3w.org</a>><br>><span =
>class=3D"Apple-converted-space"> </span><br></div></span></blockquote=
>></div><br></div></body></html>=
>
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