Re: Help on disassembler/decompilers

In article <2900@network.ucsd.edu> raul@sdnp1.ucsd.edu (Raul Rathmann) writes:
>Getting it from assembly to C was pretty difficult and was
>mostly an intuitive operation. To make a program that automatically did
>this would probably be a major undertaking and even then I don't think it
>would be able to figure out certain things.


As I've pointed out before, someone once wrote a decompiler for the VAX,
which I've played with. It *knew* how PCC generated code, so, after
"disassembling" (internal use only, generally; it didn't try to decompile
assembly text, in other words), so it would structure the code generated
from that.


It's really not that difficult thing to do, if you don't have to deal with
esoteric instructions and a smart compiler.


Oh, yeah: it didn't use the symbol table, and the code it generated
certainly had some, uhm, quirks. Variable names such as 'r0' through 'r15',
for example (except for global variables, that is). Structure members were
considered different variables (I once tried decompiling fork.o, for
example; something like three quarters of the variables were offsets into
the user structure, and I came up with a little chart that had the offsets
(and sizes) of all the elements). Etc.


But it did work. Thus borneth BSD Empire.


--
Sean Eric Fagan, seanf@sco.COM, uunet!sco!seanf, (408) 458-1422
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