[Mono-bugs] [Bug 487410] mprof-decoder finds unknown directive LAST

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http://bugzilla.novell.com/show_bug.cgi?id=487410

User massi at ximian.com added comment
http://bugzilla.novell.com/show_bug.cgi?id=487410#c3


Massimiliano Mantione <massi at ximian.com> changed:

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--- Comment #3 from Massimiliano Mantione <massi at ximian.com>  2009-04-22 02:09:46 MDT ---
I see what you mean by "graceful degradation".

However in this case I don't think it's feasible.
Or, better, we are *already* degrading gracefully: the decoder works if it does
not see new profiler features in the mprof file.

I could have used a simple version number, then the decoder would stopped
working completely on newer mprof file versions.
Instead I write in the log file some sort of "flags" (the directives) that
instruct the decoder about file format changes, and I write them only if the
feature is actually used in the file.

This way an old decoder will work also on newer "file versions" as long as the
file format is compatible.
But if the byte format has changed, well... you really need a new decoder.
The directive is there to tell the old decoder "please give up, this file is
just rubbish for you".

Of course the error message should suggest you that you need a new decoder, on
this you are right, the solution is not self-evident.
I'll surely change the error message :-)

Does this make sense?

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