The Trunk: Kernel-ct.1296.mcz

Marcel Taeumel uploaded a new version of Kernel to project The Trunk:
http://source.squeak.org/trunk/Kernel-ct.1296.mcz

==================== Summary ====================

Name: Kernel-ct.1296
Author: ct
Time: 27 January 2020, 12:59:15.057199 pm
UUID: e60f4637-b4fc-9947-94d3-50e7aa58ab82
Ancestors: Kernel-tonyg.1293

Fixes context simulation bug in #contextEnsure: and #contextOn:do:

As ctxt is *not* a top context as required by #jump, we need to put a (fake) return value (nil) on its stack. Otherwise, #jump will pop something different from the stack. Concretely, this caused the bug described in [1] (Scenario 1) because the latest stack top was the closure vector {chain}. This closure vector was accidently popped away so that in the final return statement, #pushRemoteTemp:inVectorAt: raised an error subscript bounds (because the next stack item was not variable). Read the linked bug report for more details.

[1] http://forum.world.st/BUG-s-in-Context-control-jump-runUntilErrorOrReturnFrom-td5107263.html

=============== Diff against Kernel-tonyg.1293 ===============

Item was changed:
  ----- Method: Context class>>contextEnsure: (in category 'special context creation') -----
  contextEnsure: block
  "Create an #ensure: context that is ready to return from executing its receiver"
 
  | ctxt chain |
  ctxt := thisContext.
+ [chain := thisContext sender cut: ctxt.
+ ctxt push: nil.
+ ctxt jump] ensure: block.
- [chain := thisContext sender cut: ctxt. ctxt jump] ensure: block.
  "jump above will resume here without unwinding chain"
  ^ chain!

Item was changed:
  ----- Method: Context class>>contextOn:do: (in category 'special context creation') -----
  contextOn: exceptionClass do: block
  "Create an #on:do: context that is ready to return from executing its receiver"
 
  | ctxt chain |
  ctxt := thisContext.
+ [chain := thisContext sender cut: ctxt.
+ ctxt push: nil.
+ ctxt jump] on: exceptionClass do: block.
- [chain := thisContext sender cut: ctxt. ctxt jump] on: exceptionClass do: block.
  "jump above will resume here without unwinding chain"
  ^ chain!