Re: get/set wrap methods.

[Pavlo Solntsev <pavlo solntsev gmail com>]

Just submitted a patch for a macro to generate setter for char* member in consistent way. Please review.
https://bugzilla.gnome.org/show_bug.cgi?id=793778

-Pavlo Solntsev

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On Fri, Feb 23, 2018 at 10:12 AM, Pavlo Solntsev <pavlo solntsev gmail com> wrote:

Perfect! Now I understand the methodology to implement setter for a structure. Do you think it would make sense to have a macro for this?  Say, _MEMBER_SET_CHAR. 

-Pavlo Solntsev

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On Fri, Feb 23, 2018 at 9:43 AM, Kjell Ahlstedt <kjellahlstedt gmail com> wrote:

Den 2018-02-23 kl. 15:36, skrev Pavlo Solntsev:

>>>  Your concern is justified. The Glib::ustring must be returned by value. The _MEMBER_GET should be

It is interesting. getter must return by value....

>>> Your _MEMBER_SET macro doesn't seem to fit the generated code that you show. I would think that
>>>  _MEMBER_SET(name, name, const Glib::ustring&, gchar*)

from https://github.com/GNOME/glibmm/blob/master/tools/m4/member.m4

My understanding that the generated type will be const T& if T is provided to the macros. 

dnl Creates accessors for simple types:
	define(`_MEMBER_SET',`dnl
	ifelse(`$5',`deprecated',`_DEPRECATE_IFDEF_START ')dnl
	void set_$1(const $3`'& value);
	ifelse(`$5',`deprecated',`_DEPRECATE_IFDEF_END ')dnl
	_PUSH(SECTION_CC)
	ifelse(`$5',`deprecated',`_DEPRECATE_IFDEF_START ')dnl
	void __CPPNAME__::set_$1(const $3`'& value)
	{
	gobj()->$2 = _CONVERT($3,$4,`value');
	}
	ifelse(`$5',`deprecated',`_DEPRECATE_IFDEF_END ')dnl
	_POP()')

Sorry, I was wrong. _MEMBER_SET(name, name, Glib::ustring, gchar*)
does generate the code you showed.

>> would generate that code. In this case a reference is OK, but it looks like the generated code can cause a memory leak. Who owns the duplicated string? Who deallocates it? What if gobj()->name contains a pointer to a string when set_name() is called?

Basically once again, return by value. What would be the correct wrap for the simple struct? Wrap struct and manually wrap set/get method?

I will investigate how private members are stored and how they related to the original C struct. Thanks

In Glib::OptionEntry, _MEMBER_SET is not used for strings. Those methods are hand-coded to avoid a memory leak. Example:

void OptionEntry::set_long_name(const Glib::ustring& value)
{
  if (gobject_->long_name)
  {
    g_free((gchar*)(gobject_->long_name));
    gobject_->long_name = nullptr;
  }

  gobj()->long_name = (value).c_str() ? g_strdup((value).c_str()) : nullptr;
}

Don't ask me why value.c_str() is tested for nullptr. I don't understand. I don't think it can ever be a nullptr. And even if it is, g_strdup() can handle that.

-Pavlo Solntsev