[fpc-devel] extend unreachable code warning for more cases?
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?
Regards,
Sven
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Re: [fpc-devel] extend unreachable code warning for more cases?
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.
Regards,
Sergei
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Re: [fpc-devel] extend unreachable code warning for more cases?
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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Re: [fpc-devel] extend unreachable code warning for more cases?
26.02.2014 13:28, Sven Barth пишет:
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?
Didn't test it, but should not be difficult to fix anyway.
How does it look in light of Florian's recent work on SSA? (though it's not yet
fully in trunk AFAIK)
They are probably two independent things. I've abandoned experiments with trying to use definite
assignment analysis to determine variable lifetime.
Regards,
Sergei
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[fpc-devel] Class property and virtual getter
TSimpleModel = class(TPersistent) protected class function GetResourceClient: IResourceClient; virtual; class property ResourceClient: IResourceClient read GetResourceClient; public end; Trying to compile the above code i get the following error: Error: Illegal symbol for property access Changing the GetResourceClient method from virtual to static works Is this a bug or by design? Luiz ___ fpc-devel maillist - fpc-devel@lists.freepascal.org http://lists.freepascal.org/cgi-bin/mailman/listinfo/fpc-devel
