2014-07-13 16:22 GMT+02:00 David T. Lewis lewis@mail.msen.com:
On Sun, Jul 13, 2014 at 09:55:41AM -0400, David T. Lewis wrote:
On Sun, Jul 06, 2014 at 12:47:25PM -0400, David T. Lewis wrote:
On Sun, Jul 06, 2014 at 12:23:11PM -0400, David T. Lewis wrote:
On Sun, Jul 06, 2014 at 10:34:15AM +0200, Nicolas Cellier wrote:
2014-07-04 0:47 GMT+02:00 Nicolas Cellier < nicolas.cellier.aka.nice@gmail.com>:
2014-07-04 0:09 GMT+02:00 Eliot Miranda <eliot.miranda@gmail.com
:
> > > On Thu, Jul 3, 2014 at 12:33 PM, Nicolas Cellier < > nicolas.cellier.aka.nice@gmail.com> wrote: > >> The bug is repeatable, i simply have to execute this snippet
with my
>> test file: >> >> (FileStream fileNamed: 'snapshot.bin') binary
contentsOfEntireFile
>> asString zipped. >> >> The file is too big for an attachment here - 7.3 Mbytes - or
1.7 Mbytes
>> gzipped by external tool. >> If someone can suggest an upload site, or want it by mail,
just ask.
>> > > You're welcome to put it on ftp.mirandanamda.org, cogftpuser,
pw cogging
> with 0's & 1's. > > done, pollution of your site engaged... Thanks Eliot!
>
I inquired a bit more about this bug. An important clue is that it does not happen in Pharo3.0!
But Pharo3.0 did not fundamentally change compression (except some FileSystem related changes, separation of CRC stuff
in another
package, some other cosmetic changes like replacing some self
assert: ...
by [...] assert and a potential bug in DeflateStream>>nextPutAll:startingAt: introduced by CamilleTeruel). Squeak behavior is presumably not due to a Compression change.
Neither is it a VM problem, the bugs still shows up when running
the Squeak
image with Pharo VM.
Yes, it is definite a problem in the Squeak trunk image.
So the difference lies somewhere else: in our beloved Stream. I remembered a recent change of Eliot related to handling of
Stream created
with on:from:to: (Collections-eem.567). Reverting those changes just make the snippet pass!
Ah ah! At the time, i found the change of Eliot quite minimal and
nice.
But I wish I had time to analyze this small innocent change deeper. Indeed, I remembered I previously broke my teeth on this one 2
years or so
ago, and preferred to adopt another strategy: avoid using
on:from:to: and
ReadWriteStream as much as possible. Why? because when analyzing the usage of inst.var. in Stream
hierarchy, it
gave me headaches, some subclass are just ignoring superclass
variables, or
worse are bending the semantics of superclass variables. I came to the conclusion that I could not decently master a change
of
on:from:to:
I can not confirm this. I have an image in which I can reliably
reproduce the
failure in writing the MCZ to a file. I tried reverting the methods
that were
introduced in Collections-eem.567 and I am still getting the same
failure.
Dave
Oops, I spoke too soon. Indeed the problem appears as of
Collections-eem.567,
and does not appear in Collections-nice.566.
So I am confirming Nicolas' observations ... now to find the bug :)
Dave
This seems to be a rather tricky bug, and I don't think any of us knows
the
cause right now. In case anyone else wants to have a look at it, here is
a
recipe for reproducing the bug in a clean 4.5 image:
Start with a clean Squeak 4.5 image in and empty working directory. ftp://ftp.squeak.org/4.5/Squeak4.5-13680.zip
Open the image, do not update it.
Open an MC browser and add the http://source.squeak.org/trunk
repository for the Help-Squeak-Project package and Collections package.
Load Help-Squeak-Project-kfr.18 from trunk.
Load Collections-eem.567 from trunk.
Open a browser on class SqueakToolsDebuggerHelp, and delete the class
side method #showDebuggerMenuForm.
- Remove the http://source.squeak.org/trunk repository form the
Help-Squeak-Project package in the MC browser.
- Highlight your package-cache repository and try to save
Help-Squeak-project to the package-cache repository.
Enter author initials 'dtl'.
For the package comment, enter 'Remove unreferenced method'.
Package save will fail part way through saving the MCZ.
To reproduce the failure in this image, do the following in a
workspace:
mcv := MCVersion allInstances detect: [:e | e name = 'a
MCVersion(Help-Squeak-Project-dtl.19)'].
[f := FileStream fileNamed: 'junk.mcz'. mcv fileOutOn: f] ensure: [f close].
In addition to the above recipe, here are some other observations:
Reverting from Collections-eem.567 to Collections-nice.566 makes the problem go away, but ONLY if the DeflatePlugin is active.
The failure appears while executing the fallback code for
#primitiveDeflateBlock in ZipWriteStream>>deflateBlock:chainLength:goodMatch:
If this primitive is deactivate by commenting out the <primitive: 'primitiveDeflateBlock' module: 'ZipPlugin'> in ZipWriteStream>>deflateBlock:chainLength:goodMatch: then the problem will occur regardless of which version of Collections is loaded.
When Collections-eem.567 is loaded, the primitive will fail on the 22nd call to #deflateBlock:chainLength:goodMatch: and a debugger appears
during execution of the fallback code.
- When Collections-nice.566 is loaded, the primitive does not fail on the
22nd call to #deflateBlock:chainLength:goodMatch:, the fallback code is never run, and no error appears.
- When Collections-nice.566 is loaded and the primitive is disabled to
force use of the fallback code, the error appears on on the 22nd call to #deflateBlock:chainLength:goodMatch: in exactlly the same place as when Collections-eem.567 is loaded.
- If I inspect the ZipWriteStream at the failure point (when the debugger
pops up after the problem), I see no obvious difference in the state of the stream between the Collections-eem.567 case versus the Collections-nice.566 with primitive disabled case.
Dave
Very good mining work!
When I hear Stream, I think fluid... But these snags make it so viscous, it's like our Stream is going to freeze soon. Or is it more than frozen? The vein you're after sounds as hard as diamond, we gonna need a sharp peak pickaxe.