[Vm-dev] Problem in newspeak cogit code generation

David T. Lewis lewis at mail.msen.com
Sun Oct 27 18:58:48 UTC 2019

On Sat, Oct 26, 2019 at 11:45:08PM +0200, Nicolas Cellier wrote:
> Hi all,
> I see what looks like a big problem in those files:
> https://raw.githubusercontent.com/OpenSmalltalk/opensmalltalk-vm/Cog/nsspur64src/vm/cogitX64SysV.c
> https://raw.githubusercontent.com/OpenSmalltalk/opensmalltalk-vm/Cog/nsspursrc/vm/cogitIA32.c
> The generated code for genSendDirectedSuper:numArgs: is bogus.
> the 3 instance variables
> - directedSendUsesBinding
> - directedSuperSendTrampolines
> - directedSuperBindingSendTrampolines
> have been translated into local (thus uninitialized) variables...
> How can this possibly work?
> Is it related to the CI failures?

Very likely the variables are being generated as local because they are
not referenced elsewhere. For example, directedSuperSendTrampolines is
initialized in simulation only by Cogit>>setInterpreter: but apparently
is not set anywhere in the actual translated code.

I don't think that uninitialized locals are set to null in C, so yes
this could be a source of random behavior in the CI tests.

A solution would be to initialize the three variables, possibly just
by referencing them explicitly in one of the declareCVarsIn: methods.


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