Re: [Vala] memory management class struct

[Yu Feng <rainwoodman gmail com>]

On Sat, 2008-08-23 at 10:00 -0300, Martin (OpenGeoMap) wrote:
> Hi:
> 
> Someone know how c++ manage the member in classes. 
You might want to read this.
http://en.wikipedia.org/wiki/Virtual_table

Look at the examples section. The vtable pointer in is similar to
GTypeInstance member in GLib.

I guess if there is no virtual member functions, there is no
GTypeInstance alike field in C++(gcc at least)'s memory layout. I didn't
find a ref source to support my assumptions.

For your case if you don't use any features that requires a vtable, each
of your lidar point object will use sizeof(GTypeInstance) less memory in
g++ than in GLib. A overhead of around several mega bytes for GLib code.

Yu
> I am asking this 
> because in vala i know member funcions in classes are shared between all 
> objects. This is important for me because if i want build engineering 
> apps i use many entities of the same class. For example for the lidar 
> point class i have to use 1 million of instances of the same class.
> 
> I see blender is 100% C source code in the kernel, but for example K-3D 
> is C++ pure code with extensive use of STL.
> I know microstation kernel is C pure code because i have the header of 
> all entities of the DGN format and itś only C structs.
> 
> /* Our "Instance struct" defines all the data fields that make our object unique. */f 
> typedef struct _SomeObject SomeObject;
> struct _SomeObject
> {
> 	GTypeInstance	gtype;
> 
> 	gint 		m_a;
> 	gchar*		m_b;
> 	gfloat		m_c;
> };
> 
> /* Our "Class struct" defines all the method functions that our objects will share. */
> typedef struct _SomeObjectClass SomeObjectClass;
> struct _SomeObjectClass
> {
> 	GTypeClass	gtypeclass;
> 
> 	void		(*method1)	(SomeObject *self, gint);
> 	void		(*method2)	(SomeObject *self, gchar*);
> };
> 
> 
> 
> Regards.
> 
> 
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