On 12/28/2012 06:49 PM, julien2412 wrote:
By reading the function MigrationImpl::subtract in
desktop/source/migration/migration.cxx, see
http://opengrok.libreoffice.org/xref/core/desktop/source/migration/migration.cxx#847
I thought about this patch to use "set_difference"
desktop_patch.txt
<http://nabble.documentfoundation.org/file/n4026318/desktop_patch.txt>
The original code is broken to begin with, as it ignores the return
values from the std::unique calls, so excess elements remain at the end
of va and vb.
However, the patch is also broken:
* Why "vb.end()+5"?
* The output range of std::set_difference must not overlap with either
input range.
* The return value of std::set_difference must be observed, to cut off
excess elements at the end of the returned range.
* If va contains m identical elements and vb contains n < m elements
identical to them, m - n of those elements will remain in the output of
std::set_difference, so avoiding std::unique is unsound here.
Stephan
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