在派生的class中分配虚方法时如何处理"incompatible pointer type"？

Question

我有 GLib classes Foo 和 DerivedFoo.

Fooclass有一个bar ()方法：

typedef struct _FooClass
{
  GObjectClass parent_class;

  void (*bar) (Foo *self);
} FooClass;

DerivedFooclass派生自Foo并实现了bar ()方法：

void derived_foo_bar (DerivedFoo *self);

static void
derived_foo_class_init (DerivedFooClass *klass)
{
  FooClass *foo_class = FOO_CLASS (klass);
  // Compiler warning appears here
  foo_class->bar = derived_foo_bar;
}

警告信息是：

warning: assignment from incompatible pointer type

指针不兼容，因为 self 参数的类型不同（Foo * 与 DerivedFoo *）。

这是在 GObject 中实现虚方法的正确方法吗？

如果是这样，can/should我对编译器警告做些什么？

Answer 1

您保留函数原型以尊重虚拟基础 class，并使用 glib macros/functions.

在您的函数中对其进行类型转换

void derived_foo_bar (Foo *self);

static void
derived_foo_class_init (DerivedFooClass *klass)
{
  FooClass *foo_class = FOO_CLASS (klass);
  // Compiler warning appears here
  foo_class->bar = derived_foo_bar;
}

void derived_foo_bar (Foo *_self)
{
  DerivedFoo *self = DERIVED_FOO (self); /* or whatever you have named this macro, using the standard GLIB semantics */
 /* If self is not compatible with DerivedFoo, a warning will be issued from glib typecasting logic */
}

在派生的class中分配虚方法时如何处理"incompatible pointer type"？

How to deal with "incompatible pointer type" when assigning virtual methods in a derived class?

c

compiler-warnings

glib

gobject

virtual-functions