Hi all,
Can anyone does the favour for me by explaining the story of RuntimeTypeInfo in
RPython?
I couldn’t quite understand the description on the online documentation
(http://rpython.readthedocs.io/en/latest/rtyper.html#opaque-types). From
looking at the source code, and inspecting the generated C source, RTTI doesn’t
seem to be used at all at runtime. The generated C source seems to just return
an uninitialised function pointer on the stack when compiling the following
code:
from rpython.rtyper.rclass import OBJECTPTR
class A:
pass
class B(A):
pass
def f(a):
obj = rffi.cast(OBJECTPTR, a)
return lltype.runtime_type_info(obj)
t = Translation(f, [A], backend='c')
t.backendopt(mallocs=True)
t.view()
lib = t.compile()
We were looking at RTTI in finding a solution to the loss of type information
problem at JIT encoding. My collaborators are trying to develop a JIT back-end
targeting a micro virtual machine (Mu). It seems that by default the JIT
transformer throws away the actual type information (GcStruct etc., which is
not representable under RPython, I know) and only keeps the size. However, in
Mu, memory allocation requires specific type information. Thus, among other
ways, we are trying to see how much we can recover this object layout/type
information. RTTI seems promising based on the description on the
documentation, but I can’t picture what it looks like at run time.
Can anyone provide some insight on this?
Thanks,
John Zhang
------------------------------------------------------
John Zhang
Research Assistant
Programming Languages, Design & Implementation Division
Computer Systems Group
ANU College of Engineering & Computer Science
108 North Rd
The Australian National University
Acton ACT 2601
john.zh...@anu.edu.au<mailto:john.zh...@anu.edu.au>
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