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Setup showstopper

     Hey all,

  As long as we're talking about setup, let me raise the one I've just run

  When there's an error validating the checksum of a package (to be precise,
when validateCachedPackage() returns an error indication to
check_for_cached() in, setup raises an exception and aborts,
because there's no handler to catch it.  For example:

Fatal Error: Uncaught Exception
Thread: DialogProc
Type: 9Exception
Message: Package validation failure for
AppErrNo: 1

  This isn't very helpful, as it will only fail again in the same way next
time it gets to try and validate that package.

  In other words, a validation error becomes permanent and fatal and there's
no way to ever recover/repair/upgrade/revert your cygwin installation
without manually going into the local package dir, finding the relevant
file, and getting rid of it.  Which is not newbie-friendly.  (It can of
course be worked around with --no-md5, but no newbie is going to type "setup
--help" and guess where the hell the output has gone!).

1)  Wouldn't the best thing be to just delete (or rename-aside, or even
ignore) the apparently-corrupt package?

2)  check_for_cached is supposed to return 0 for failure.  Why is it
throwing an exception?

3)  The functions download_one and do_download_thread, which call
check_for_cached, do in fact wrap the call in try...except handlers, but as
soon as they catch the exception they pass it straight to fatal (...); why
should it be regarded as a fatal error?

4)  The only function to call check_for_cached as an extern is
packageversion::scan in package_version.h; this function fails to wrap it in
any kind of exception handler at all, which is presumably because someone
looked at the check_for_cached function, saw the comment about "Return 0 for
failure", and didn't look through the source and see that it might also
raise an exception.  (This is a good argument against ever using two
different and non-commensurate mechanisms to return error indications from a
function, incidentally!)

  So, what do you reckon?  Should I make check_for_cached just quietly
return zero if the package validates wrong?  That would (I think) have the
effect of making setup redownload the package and overwrite the old corrupt
one, wouldn't it?  

  Or should I leave it to the callers to decide what to do, but perhaps find
a better error return mechanism (zero for 'not found', -ve for 'error', +ve
for 'success' perhaps?) that's more logical and maintainable?

  Perhaps a corrupted package be warned about, with a "Rename/Delete/Ignore"

Can't think of a witty .sigline today....

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