#789: Make All PMCs Subclassable
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Reporter: whiteknight | Owner:
Type: todo | Status: new
Priority: normal | Milestone: 2.0
Component: none | Version: 1.3.0
Severity: medium | Keywords: pmc subclass
Lang: | Patch:
Platform: |
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Several core PMC types are not subclassable because they have attributes
that are not the "register" types (P, S, N, I). What happens is that the
subclass operation acts like normal, but Objects of the resultant class
are not usable for normal operations.
Some examples:
- FileHandle (see #681)
- ExceptionHandler (See #154)
Any other PMC type that uses a non-subclassable ATTR will have the same
problem, although to my knowledge no tickets for these have been opened
yet.
I had been working in #681 in a branch, but after talking with Allison we
decided that the approach had the right idea but the wrong implementation.
From IRC today (paraphrased):
{{{
allison> give PIR Classes the ability to create a delegate or proxy
structure for ATTRs that aren't register types
allison> the basic problem is, attributes in PIR Classes are stored in an
array
allison> That array can only have PMC elements
allison> so, it knows how to box and unbox the basic register types
whiteknight> so do something like box C types into ManagedStruct or
something similar?
allison> the best place to start is probably with a list of C types in the
current C PMCs, and how they can be represented as a PMC
}}}
See the whole discussion here:
[http://irclog.perlgeek.de/parrot/2009-06-24#i_1263385]
So here's a quick list of tasks that we can do to fix this problem:
# Get a list together of all ATTRs in built-in PMC types that are not
INTVAL, FLOATVAL, STRING* or PMC*
# Determine how to store each of those types in PMCs. This could mean
using ManagedStruct or UnmanagedStruct, Pointer, CPointer, or some new
type entirely
# Teach the GETATTR/SETATTR macros how to access values that are boxed
like this.
This whole process probably requires a little bit more thought and
planning, I'll try to create a page on the wiki somewhere so that we can
plan this in more detail.
--
Ticket URL: <https://trac.parrot.org/parrot/ticket/789>
Parrot <https://trac.parrot.org/parrot/>
Parrot Development
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