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Represent empty shared pointers by null pointers at C level

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This is much more convenient and allows checking if the shared pointer
is empty easily, unlike before, when it couldn't be done and adding
support for it would have required adding extra functions.

Also add a way to check whether an object is null in C++ wrappers of the
classes handled via shared pointers and static null() method for
creating null objects of such classes.
This commit is contained in:
Vadim Zeitlin 2021-12-06 21:52:21 +01:00
commit b072b2dc87
1 changed files with 20 additions and 3 deletions
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23
Lib/c/std_shared_ptr.i
View file

@ -17,9 +17,20 @@
SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE >*
"$typemap(ctype, TYPE)";
// Typemap for smart pointer type itself.
%typemap(out) SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE >
"$result = new $1_ltype($1);"
// Typemap for smart pointer type itself: these are somewhat special because we represent empty shared pointers as null pointers at C level because there is
// no advantage in using a non-null pointer in this case, while testing for NULL is much simpler than testing whether a shared pointer is empty.
%typemap(in) SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE > (SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE > empty) %{
$1 = $input ? *(SWIG_SHARED_PTR_QNAMESPACE::shared_ptr<CONST TYPE>*)$input : empty; %}
%typemap(in) const SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE >& (SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE > empty) %{
$1 = $input ? (SWIG_SHARED_PTR_QNAMESPACE::shared_ptr<CONST TYPE>*)$input : &empty; %}
// Note that "&" here is required because "$1" ends up being SwigValueWrapper and not the shared pointer itself. This is wrong and should be fixed by disabling
// the use of SwigValueWrapper for shared pointers entirely, as it's never needed for them.
%typemap(out) SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE > %{ $result = (&$1 ? new $1_ltype($1) : 0); %}
// Use of "*" here is due to the fact that "$1" is a pointer, but we want to test the smart pointer itself.
%typemap(out) const SWIG_SHARED_PTR_QNAMESPACE::shared_ptr<CONST TYPE>& %{ $result = (*$1 ? $1 : 0); %}
// And for the plain type.
%typemap(in) CONST TYPE (SWIG_SHARED_PTR_QNAMESPACE::shared_ptr< CONST TYPE > *smartarg = 0) %{
@ -50,6 +61,12 @@
%typemap(out, fragment="SWIG_null_deleter") CONST TYPE & %{
$result = (SwigObj*) new SWIG_SHARED_PTR_QNAMESPACE::shared_ptr<CONST TYPE >($1 SWIG_NO_NULL_DELETER_$owner);%}
// Allow creating null shared pointers and testing them for validity.
%typemap(cxxcode) TYPE %{
static $cxxclassname null() { return $cxxclassname{($cclassptrname)nullptr, false}; }
explicit operator bool() const { return swig_self_ != nullptr; }
%}
%enddef
%include <shared_ptr.i>