[GiNaC-devel] remove_dirac_ONE() and documentation patches

[Vladimir V. Kisil]

	Dear Alexey,

	Many thanks for the useful suggestions. I have revised my patch
  in accordance with your first suggestion: both the old and the new
  version are present. This patch is attached below.

  Regarding crashes of my application the situation was solved by
  partial substitution: I was able to avoid crashes keeping the original
  version of GiNaC. It was enough to replace calls to exception-free
  version of remove_dirac_ONE to in my library only. Probably exceptions
  work fine within one library but create crashes if passed between
  different libraries.

  Best wishes,
  Vladimir
-- 
Vladimir V. Kisil                 http://www.maths.leeds.ac.uk/~kisilv/
  Book:     Geometry of Mobius Transformations     http://goo.gl/EaG2Vu
  Software: Geometry of cycles          http://moebinv.sourceforge.net/
>>>>> On Sun, 19 May 2019 19:31:06 +0400, Alexey Sheplyakov <asheplyakov at yandex.ru> said:

    ASh> Hi,


    >>   Thus I re-write remove_dirac_ONE() without exceptions. The
    >> signature   of the method has to change, but a user may not
    >> notice this in the   first approximation.

    ASh> There a few fatal differences (which are indeed not so easy to
    ASh> spot):

    ASh> - A user code might be relying on remove_dirac_ONE() to throw
    ASh> an exception when something goes wrong.  The patch breaks such
    ASh> a code without a slightest warning from the compiler.

    ASh> - Before the patch this:

    ASh>   remove_dirac_ONE(e, 0, 0);

    ASh>   used to compile and work just fine. With the patch it also
    ASh> compiles (without a slightest warning), and segfaults at the
    ASh> run time (for the last 0 is `bool *success` now).0


    >> * @param e Expression to be processed - * @param rl Value of
    >> representation label - * @param options Defines some internal use
    >> */ -ex remove_dirac_ONE(const ex & e, unsigned char rl = 0,
    >> unsigned options = 0); + * @param rl Value of representation
    >> label, all dirac_ONE with this or greater value will be processed
    >> + * @param success It is changed to false if there is at least
    >> one clifford_unit() in the expression + * @param options Defines
    >> some internal value for recursive calls, shall be ommited in user
    >> code */ +ex remove_dirac_ONE(const ex & e, unsigned char rl = 0,
    >> bool *success = new bool, unsigned options = 0);

    ASh> Also there's a memory leak (since nobody is going to release
    ASh> that `new bool`).

    ASh> Therefore I think the patch is wrong and should not be applied.

    ASh> Possible solutions:

    ASh> 1)

    ASh> a) Make a new (overload of) remove_dirac_ONE function:

    ASh>     ex remove_dirac_ONE(const ex& e, bool& success, unsigned
    ASh> char rl = 0, unsigned options = 0);

    ASh>    which reports errors without exceptions

    ASh> b) Don't change the behavior of the existing `ex
    ASh> remove_dirac_ONE(const ex& e, unsigned char rl =0, unsigned
    ASh> options = 0);

    ASh> 2) Leave current `remove_dirac_ONE` as is. It's not broken,
    ASh> there's nothing to fix.

    >> The exceptions in remove_dirac_ONE() terminated a Qt Windows
    >> application

    ASh> And fix that application instead (perhaps I could help if the
    ASh> sources and instructions how to reproduce the problem are
    ASh> available)

    ASh> Best regards, Alexey
    ASh> _______________________________________________ GiNaC-devel
    ASh> mailing list GiNaC-devel at ginac.de
    ASh> https://www.cebix.net/mailman/listinfo/ginac-devel
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