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Improve documentation of 'emacs_function' in modules

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* doc/lispref/internals.texi (Module Functions): Warn about
accessing the ARGS array in module functions.
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Eli Zaretskii 2024-01-13 12:01:47 +02:00
parent a08e6423cc
commit c494a6e879
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doc/lispref/internals.texi
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@ -1371,6 +1371,15 @@ objects between Emacs and the module (@pxref{Module Values}). The
provides facilities for conversion between basic C data types and the
corresponding @code{emacs_value} objects.
In the module function's body, do @emph{not} attempt to access
elements of the @var{args} array beyond the index
@code{@var{nargs}-1}: memory for the @var{args} array is allocated
exactly to accommodate @var{nargs} values, and accessing beyond that
will most probably crash your module. In particular, if the value of
@var{nargs} passed to the function at run time is zero, it must not
access @var{args} at all, as no memory will have been allocated for it
in that case.
A module function always returns a value. If the function returns
normally, the Lisp code which called it will see the Lisp object
corresponding to the @code{emacs_value} value the function returned.