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correctly document closure return promotion

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Tom Tromey
2015-12-17 16:58:10 -07:00
parent 8a7cdeb041
commit 6affad7911
1 changed files with 11 additions and 7 deletions
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18
doc/libffi.texi
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@@ -806,13 +806,17 @@ The @code{ffi_cif} passed to @code{ffi_prep_closure_loc}.
@item ret
A pointer to the memory used for the function's return value.
@var{fun} must fill this, unless the function is declared as returning
@code{void}. Note that this points to memory that is exactly the size
of the type given as the return type when initializing the CIF. In
particular, closures do not have the special promotion behavior of
@code{ffi_call}.
@c FIXME: is this NULL for void-returning functions?
@c (experimentally it is not, but it seems like a good idea)
If the function is declared as returning @code{void}, then this value
is garbage and should not be used.
Otherwise, @var{fun} must fill the object to which this points,
following the same special promotion behavior as @code{ffi_call}.
That is, in most cases, @var{ret} points to an object of exactly the
size of the type specified when @var{cif} was constructed. However,
integral types narrower than the system register size are widened. In
these cases your program may assume that @var{ret} points to an
@code{ffi_arg} object.
@item args
A vector of pointers to memory holding the arguments to the function.