[Stk] unhandled exception when using BlitSaw with std::vector
Stephen Sinclair
sinclair at music.mcgill.ca
Tue Jul 2 15:36:34 PDT 2013
My apologies, I was indeed testing this on an old version. If the
problem is rectified now, all the better! :)
Sorry about that.
Steve
On Tue, Jul 2, 2013 at 4:59 PM, Nick Dika <nhdika at gmail.com> wrote:
> Hi Gary,
>
> Thanks for looking into this. I thought I was on the latest version, but
> looks like i'm on 4.4.3 -- perhaps whoever wrapped STK up as a Juce module
> hasn't updated it to the latest version. Let me see if I can get 4.4.4
> working with Juce. In the meantime, I'm curious to see if Stephen is also on
> an older version ...
>
> nick
>
>
> On Tue, Jul 2, 2013 at 10:43 AM, Gary Scavone <gary at ccrma.stanford.edu>
> wrote:
>>
>> Hi Nick and Stephen,
>>
>> I didn't have a problem compiling and running either example using gcc
>> 4.2.1 on OS-X. Again, did you check to make sure you were using the latest
>> release of STK?
>>
>> --gary
>>
>> On 2013-06-19, at 12:43 PM, Stephen Sinclair <sinclair at music.mcgill.ca>
>> wrote:
>>
>> > By the way, I tried compiling STK without the errorString_ member
>> > variable and then your initial examples worked fine. I guess the
>> > lesson is that an ostringstream is not a "value" and can't be copied,
>> > so shouldn't be used to contain data, but only to construct it.
>> >
>> > On Wed, Jun 19, 2013 at 6:03 PM, Nick Dika <nhdika at gmail.com> wrote:
>> >> Thanks Stephen for your detailed explanation. I realize what I was
>> >> doing
>> >> with the array example was sloppy, the goal was really to get it
>> >> working
>> >> with Vector and push_back() so that I can scale the container as
>> >> needed. I
>> >> will try your suggestion later and see if I'm able to get it working.
>> >>
>> >> n
>> >>
>> >>
>> >> On Wed, Jun 19, 2013 at 9:45 AM, Stephen Sinclair
>> >> <sinclair at music.mcgill.ca>
>> >> wrote:
>> >>>
>> >>> Hi Nick,
>> >>>
>> >>> On Wed, Jun 19, 2013 at 3:09 PM, Nick Dika <nhdika at gmail.com> wrote:
>> >>>> Thanks Stephen. Here's a simplified version of what I'm doing.
>> >>>>
>> >>>> This works:
>> >>>>
>> >>>> stk::BlitSaw oscArray[10];
>> >>>>
>> >>>> for( int i=0; i < 10; i++ )
>> >>>> {
>> >>>> stk::BlitSaw saw;
>> >>>> saw.setHarmonics(0);
>> >>>> saw.setFrequency(220);
>> >>>> oscArray[i] = saw;
>> >>>> }
>> >>>
>> >>> Actually in g++-4.7 at least, this code does not compile. The BlitSaw
>> >>> class is unassignable.
>> >>>
>> >>> (I'm not 100% sure why, but it seems to be because objects of class
>> >>> Stk contain a std::ostringstream member which is unassignable.)
>> >>>
>> >>>
>> >>>> This breaks:
>> >>>>
>> >>>> std::vector<stk::BlitSaw> oscs;
>> >>>>
>> >>>> for( int i=0; i < 10; i++ )
>> >>>> {
>> >>>> stk::BlitSaw saw;
>> >>>> saw.setHarmonics(0);
>> >>>> saw.setFrequency(220);
>> >>>> oscs.push_back(saw);
>> >>>> }
>> >>>
>> >>> This is effectively equivalent to the above code so I'm not 100% why
>> >>> it's breaking things but probably the object is not being properly
>> >>> copied within the vector. In particular, since you have a vector of
>> >>> instances of BlitSaw, when the internal array in the std::vector is
>> >>> re-allocated, perhaps the new, copied memory is not properly
>> >>> initialized 100%, since the object type is not assignable. Just a
>> >>> guess, but it's weird behaviour for sure, but due to undefined
>> >>> behaviour because this isn't how you should do what you're trying to
>> >>> do.
>> >>>
>> >>>>
>> >>>> the second example causes an unhandled exception/access violation
>> >>>> reading
>> >>>> from a location. As mentioned this appears to happen after
>> >>>> StkFrames::resize() is called (I don't fully understand why this
>> >>>> would
>> >>>> be
>> >>>> called).
>> >>>
>> >>> All Generators, which BlitSaw is one, have an StkFrame called
>> >>> lastFrames_, and it's resize() method is called during initialization.
>> >>> Not sure why it's leading to an exception but like your array doesn't
>> >>> contain valid BlitSaw instances.
>> >>>
>> >>> Anyways, to elaborate, the way you're initializing things isn't
>> >>> fundamentally wrong, so it could indicate some bugs somewhere, but
>> >>> it's certainly not the ideal way to work with Stk objects. You are
>> >>> creating an array of objects, such that their constructors are called,
>> >>> and then a loop you are constructing a new object on the stack,
>> >>> setting its parameters, and then copying that object over top of the
>> >>> objects already in the array and letting it destruct. Not the most
>> >>> efficient approach.
>> >>>
>> >>> (Note, your push_back() call also doesn't compile in g++-4.7.)
>> >>>
>> >>> Instead I'd suggest either directly initializing the objects that are
>> >>> already in the array, or initializing them and then storing their
>> >>> pointers in the array. i.e., either:
>> >>>
>> >>> #include <iostream>
>> >>> #include <Stk.h>
>> >>> #include <BlitSaw.h>
>> >>>
>> >>> int main()
>> >>> {
>> >>> stk::BlitSaw oscs[10];
>> >>>
>> >>> for( int i=0; i < 10; i++ )
>> >>> {
>> >>> stk::BlitSaw *saw = &oscs[i];
>> >>> saw->setHarmonics(0);
>> >>> saw->setFrequency(220);
>> >>> }
>> >>>
>> >>> return 0;
>> >>> }
>> >>>
>> >>>
>> >>> .. or ..
>> >>>
>> >>>
>> >>> #include <iostream>
>> >>> #include <memory>
>> >>> #include <Stk.h>
>> >>> #include <BlitSaw.h>
>> >>>
>> >>> int main()
>> >>> {
>> >>> std::vector<std::unique_ptr<stk::BlitSaw>> oscs;
>> >>>
>> >>> for( int i=0; i < 10; i++ )
>> >>> {
>> >>> std::unique_ptr<stk::BlitSaw> saw(new stk::BlitSaw);
>> >>> saw->setHarmonics(0);
>> >>> saw->setFrequency(220);
>> >>> oscs.push_back(std::move(saw));
>> >>> }
>> >>>
>> >>> return 0;
>> >>> }
>> >>>
>> >>>
>> >>> Steve
>> >>>
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>> >>
>> >>
>> >>
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