Age | Commit message (Collapse) | Author |
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Speaking of unclear documentation, it is not obvious whether it is
necessary for programs calling into Prolog to manually mark and
release strings. I suppose that it should be, if the same logic that
applies to terms apply to strings.
On the other hand, the stack in which the strings are stored belongs
to Prolog, and there is nothing that would prevent Prolog from
cleaning up the strings when called at a later time. I am not sure.
But better safe than sorry, I guess.
The Mark class acts like the Frame class. The constructor and
destructor are equivalent to the PL_STRINGS_MARK and
PL_STRINGS_RELEASE macros.
Unlike for 34c3280, I did not notice any differences in memory usage
after this change. Perhaps that is because it has no effect; perhaps
it is because Prolog's stack is very big.
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Apparently foreign frames ARE needed when calling Prolog from C. The
official documentation is very terse and could make this clearer.
To summarize, whenever a term is created (e.g., PL_new_term_refs), its
reference count is increased by one. It is garbage-collected when its
reference count hits zero. But the reference count is never decreased
unless (a) control returns to Prolog after executing a foreign
predicate -- which does not happen in my application -- or (b) the
foreign frame in which the term was created is closed.
In other words, terms must be created within a foreign frame. This is
achieved by initializing a Frame object before creating the term and
destroying it once the term has served its purpose.
The destructor for Frame does not DISCARD the frame, only CLOSE it.
The former would also invalidate all data bound by the terms, which is
usually undesirable.
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It seems that "right-spaced" pointers are more widely used among C++
programmers.
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Note that I did NOT add const to non-pointer/non-reference arguments
in function declarations (without a following definition), as they do
not mean anything there.
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This avoids the use of TsmFromSz.
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I.e. using std::basic_string<TCHAR> instead of TCHAR *. This removes
all unmanaged frees.
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This is feasible now that the makedeps script exists to automatically
manage build dependencies (see 6034fe2, d00f8b3).
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In the future, it may be desirable to convert Prolog exceptions to C++
exceptions.
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This is a bit safer and about as complex.
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I already hit upon some object-oriented programming patterns in
*listview.c, so I felt that it would be natural to use this as an
opportunity to learn C++.
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