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Re: Rational

From: Hans Åberg
Subject: Re: Rational
Date: Tue, 22 May 2018 23:07:58 +0200

> On 22 May 2018, at 22:53, David Kastrup <address@hidden> wrote:
>>> This was somewhat complicated by some Midi classes being heap-allocated
>>> and containing Rational/Moment members: those Midi classes would have to
>>> become SCM-connected.  I did some work on that, don't remember how
>>> complete it was.
>> Guile uses the Boehm GC.
> Not Guile 1, and LilyPond will have large amounts of heap space outside
> of Boehm's fully automated sweep areas even in Guile 2 for efficiency
> and compatibility reasons.

Something for the future then.

>> I wrote a C++ wrap for that latter, too. As it turns out to be
>> difficult to keep of pointers into the GC heap, I had to use only
>> those that it supplies. Do you do that?
> I don't know what "I had to use only those that it supplies" is supposed
> to mean, so I cannot answer the question.

In addition to the collected GC_malloc, there are GC_malloc_uncollectable and 
GC_free that correspond to malloc and free. If one uses the latter pair and 
have pointers into the GC heap, they may suddenly disappear, causing strange 
memory errors.

In addition, beware that on some platforms, the GC must be initialized before 
the first use (like on MacOS), and if one is using global C++ objects with heap 
allocations, that must occur before those being initialized, which is before 
'main' starts.

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