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Limitations of decompiling control structures.

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rocky
2016-11-27 14:20:35 -05:00
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@@ -97,7 +97,8 @@ Known Bugs/Restrictions
-----------------------
The biggest known and possibly fixable (but hard) problem has to do
with handling control flow. In some cases we can detect an erroneous
with handling control flow. All of the Python decomilers I have looked
at have the same problem. In some cases we can detect an erroneous
decompilation and report that.
About 90% of the decompilation of Python standard library packages in
@@ -109,14 +110,17 @@ Other versions drop off in quality too.
a Python for that bytecode version, and then comparing the bytecode
produced by the decompiled/compiled program. Some allowance is made
for inessential differences. But other semantically equivalent
differences are not caught. For example ``if x: foo()`` is
equivalent to ``x and foo()`` and decompilation may turn one into the
other. *Weak Verification* on the other hand doesn't check bytecode
for equivalence but does check to see if the resulting decompiled
source is a valid Python program by running the Python
interpreter. Because the Python language has changed so much, for best
results you should use the same Python Version in checking as used in
the bytecode.
differences are not caught. For example ``1 and 0`` is decompiled to
the equivalent ``0``; remnants of the first true evaluation (1) is
lost when Python compiles this. When Python next compiles ``0`` the
resulting code is simpler.
*Weak Verification*
on the other hand doesn't check bytecode for equivalence but does
check to see if the resulting decompiled source is a valid Python
program by running the Python interpreter. Because the Python language
has changed so much, for best results you should use the same Python
Version in checking as used in the bytecode.
Later distributions average about 200 files. There is some work to do
on the lower end Python versions which is more difficult for us to