wrong method trailer kind

17618 Failing test: ReleaseTest>>#testInstalledMethodsWithIncorrectTrailerKind

Interesting bug.

someone who can tell me what exactly is this trailer kind and why it is based

on some "flag" in "method at: method size".

And why it seems to be wrong for many GT-methods:

(CompiledMethod allInstances select:[:m | (m at: m size) = 24]) collect:[:k |
    k -> k trailer kind] "an Array(String class>>#gtInspectorFourtyTwo->#EmbeddedSourceQCompress OSEnvironment>>#getEnv:->#EmbeddedSourceQCompress OSEnvironment>>#getEnv:->#EmbeddedSourceQCompress GlobalVariable class>>#gtExampleSmalltalk->#EmbeddedSourceQCompress VirtualMachine class>>#gtExampleBasic->#EmbeddedSourceQCompress GLMBrowser class>>#gtExampleBasic->#EmbeddedSourceQCompress RPackageTag class>>#gtExamplePackageTag->#EmbeddedSourceQCompress Object class>>#gtExampleBasic->#EmbeddedSourceQCompress GLMCompositePresentation class>>#gtExampleCompositePresentation->#EmbeddedSourceQCompress LiteralVariable class>>#gtExampleUniqueLiteralVariable->#EmbeddedSourceQCompress GTSpotterRecorderEvent class>>#gtExampleAnySubclass->#EmbeddedSourceQCompress MetacelloAbstractPackageSpec class>>#gtExamplePackageSpec->#EmbeddedSourceQCompress MetacelloProjectReferenceSpec class>>#gtExampleProjectReferenceSpec->#EmbeddedSourceQCompress MetacelloProjectSpec class>>#gtExampleMetacelloSpec->#EmbeddedSourceQCompress MetacelloSpec class>>#gtExampleMetacelloSpec->#EmbeddedSourceQCompress MetacelloVersion class>>#gtExampleMetacelloVersion->#EmbeddedSourceQCompress GLMPresentation class>>#gtExampleBasic->#EmbeddedSourceQCompress Bag class>>#gtExampleBagWithTenElements->#EmbeddedSourceQCompress Bag class>>#gtExampleBagWithOneElement->#EmbeddedSourceQCompress GTDummyExamplesRecursive class>>#h->#EmbeddedSourceQCompress GLMAlertBrick class>>#gtExample->#EmbeddedSourceQCompress GTDummyExampleProvider>>#a->#EmbeddedSourceQCompress GTDummyExampleProvider>>#b->#EmbeddedSourceQCompress GTDummyExampleWithAssertions>>#a->#EmbeddedSourceQCompress GTDummyExampleWithAssertions>>#b->#EmbeddedSourceQCompress GTDummyExamples class>>#l->#EmbeddedSourceQCompress GTDummyExamples class>>#o->#EmbeddedSourceQCompress GTDummyExamplesInvalid class>>#a:->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#a->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#c->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#b->#EmbeddedSourceQCompress GLMCollapsableBrick class>>#gtExample->#EmbeddedSourceQCompress FileReference class>>#gtExampleText->#EmbeddedSourceQCompress GTSpotterStep class>>#gtExampleBasic->#EmbeddedSourceQCompress GTEventAnnouncement class>>#gtExampleEmptyAnnouncement->#EmbeddedSourceQCompress UndefinedObject>>#DoIt->#EmbeddedSourceQCompress UndefinedObject>>#DoIt->#EmbeddedSourceQCompress)"

Hi Nicolai,

On Fri, Feb 26, 2016 at 1:50 PM, Nicolai Hess <[hidden email]> wrote:

17618 Failing test: ReleaseTest>>#testInstalledMethodsWithIncorrectTrailerKind

Interesting bug.

someone who can tell me what exactly is this trailer kind and why it is based

on some "flag" in "method at: method size".

There's a rich class comment in CompiledMethodTrailer which explains a lot, but let me add a little.

Back in the day the source pointer in methods (the pointer that says which of the two source files and where in the file a method's source is kept) was stored in three bytes added onto the end of a CompiledMethod after its endPC.  Then Dan Ingalls added the ability to not have source files at all but just to have named temporary variables.  he added a compressed version of the temp names in bytes tacked on at the end of a method, replacing the source pointer.  IIRC the difference between a source pointer, no source pointer, or a compressed version of the temp names was all encoded in the last byte.

Round about 2009 Igor Stasenko did a really nice reimplementation of this scheme where he factored out the encoding tricks into CompiledMethodTrailer, allowing one to generalize the scheme and add new encoding types, for a total of 256 different kinds of trailer.

(and if you already know all of this, forgive me for trying to teach you to suck eggs)

Anyway this trailer is

CompiledMethodTrailer >>encodeEmbeddedSourceQCompress

"data is string with method's source code, encode it using qCompress method"

self encodeUsingQCompress

CompiledMethodTrailer >>decodeEmbeddedSourceQCompress

"data is string with method's source code, encoded using qCompress method"

self qDecompress.

HTH

And why it seems to be wrong for many GT-methods:

(CompiledMethod allInstances select:[:m | (m at: m size) = 24]) collect:[:k |
    k -> k trailer kind] "an Array(String class>>#gtInspectorFourtyTwo->#EmbeddedSourceQCompress OSEnvironment>>#getEnv:->#EmbeddedSourceQCompress OSEnvironment>>#getEnv:->#EmbeddedSourceQCompress GlobalVariable class>>#gtExampleSmalltalk->#EmbeddedSourceQCompress VirtualMachine class>>#gtExampleBasic->#EmbeddedSourceQCompress GLMBrowser class>>#gtExampleBasic->#EmbeddedSourceQCompress RPackageTag class>>#gtExamplePackageTag->#EmbeddedSourceQCompress Object class>>#gtExampleBasic->#EmbeddedSourceQCompress GLMCompositePresentation class>>#gtExampleCompositePresentation->#EmbeddedSourceQCompress LiteralVariable class>>#gtExampleUniqueLiteralVariable->#EmbeddedSourceQCompress GTSpotterRecorderEvent class>>#gtExampleAnySubclass->#EmbeddedSourceQCompress MetacelloAbstractPackageSpec class>>#gtExamplePackageSpec->#EmbeddedSourceQCompress MetacelloProjectReferenceSpec class>>#gtExampleProjectReferenceSpec->#EmbeddedSourceQCompress MetacelloProjectSpec class>>#gtExampleMetacelloSpec->#EmbeddedSourceQCompress MetacelloSpec class>>#gtExampleMetacelloSpec->#EmbeddedSourceQCompress MetacelloVersion class>>#gtExampleMetacelloVersion->#EmbeddedSourceQCompress GLMPresentation class>>#gtExampleBasic->#EmbeddedSourceQCompress Bag class>>#gtExampleBagWithTenElements->#EmbeddedSourceQCompress Bag class>>#gtExampleBagWithOneElement->#EmbeddedSourceQCompress GTDummyExamplesRecursive class>>#h->#EmbeddedSourceQCompress GLMAlertBrick class>>#gtExample->#EmbeddedSourceQCompress GTDummyExampleProvider>>#a->#EmbeddedSourceQCompress GTDummyExampleProvider>>#b->#EmbeddedSourceQCompress GTDummyExampleWithAssertions>>#a->#EmbeddedSourceQCompress GTDummyExampleWithAssertions>>#b->#EmbeddedSourceQCompress GTDummyExamples class>>#l->#EmbeddedSourceQCompress GTDummyExamples class>>#o->#EmbeddedSourceQCompress GTDummyExamplesInvalid class>>#a:->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#a->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#c->#EmbeddedSourceQCompress GTDummyExamplesPragmas class>>#b->#EmbeddedSourceQCompress GLMCollapsableBrick class>>#gtExample->#EmbeddedSourceQCompress FileReference class>>#gtExampleText->#EmbeddedSourceQCompress GTSpotterStep class>>#gtExampleBasic->#EmbeddedSourceQCompress GTEventAnnouncement class>>#gtExampleEmptyAnnouncement->#EmbeddedSourceQCompress UndefinedObject>>#DoIt->#EmbeddedSourceQCompress UndefinedObject>>#DoIt->#EmbeddedSourceQCompress)"

_,,,^..^,,,_

best, Eliot