Am 26.02.2014 09:41, schrieb Sergei Gorelkin:
26.02.2014 12:09, Sven Barth пишет:
Hello together!
In context of Apple's recent security bug where a "goto fail;" at the
wrong place disabled
certificate checking or something along that lines I've thought
whether it would 1) be worthwhile to
extend FPC with the capability to detect such cases as well and 2) to
see whether it would be
currently feasible at all.
So, how hard would it be to let the compiler detect cases like these:
=== code begin ===
procedure Test1;
begin
Writeln('Test1');
Exit;
Writeln('Test1');
end;
procedure Test2;
label
stop;
begin
Writeln('Test2');
goto stop;
Writeln('Test2');
stop:
end;
=== code end ===
and of course potentially more complex ones...
Also would you think it would be worthwhile to spend time on this?
The definite assignment analysis ported by me four years ago
(http://bugs.freepascal.org/view.php?id=15523) detects all cases of
unreachable code, except backward goto's. Everything but backward
goto's is almost trivial, backward goto's are more complicated because
they require multiple iterations over code tree, but are certainly
feasible.
Nice... does that code still work with current trunk? How does it look
in light of Florian's recent work on SSA? (though it's not yet fully in
trunk AFAIK) Could your DFA be combined combined with the current DFA so
that we would have both definite assignment analysis and live variable
analysis? [ok, after reading your first comment it should be possible]
Since you now have write access to SVN you could finally use a branch
for this. :)
Regards,
Sven
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