core.attribute

This module contains UDA's (User Defined Attributes) either used in the runtime or special UDA's recognized by compiler.

License:

Boost License 1.0

Authors:

Jacob Carlborg

Source

core/attribute.d

struct selector;

Use this attribute to attach an Objective-C selector to a method.

This is a special compiler recognized attribute, it has several requirements, which all will be enforced by the compiler:

• The attribute can only be attached to methods or constructors which have Objective-C linkage. That is, a method or a constructor in a class or interface declared as

  extern(Objective-C)

  .
,


• It cannot be attached to a method or constructor that is a template
,


• The number of colons in the string need to match the number of arguments the method accept.
,


• It can only be used once in a method declaration

Examples:

extern (Objective-C)
class NSObject
{
 this() @selector("init");
 static NSObject alloc() @selector("alloc");
 NSObject initWithUTF8String(in char* str) @selector("initWithUTF8String:");
 ObjcObject copyScriptingValue(ObjcObject value, NSString key, NSDictionary properties)
     @selector("copyScriptingValue:forKey:withProperties:");
}

enum optional;

Use this attribute to make an Objective-C interface method optional.

An optional method is a method that does not have to be implemented in the class that implements the interface. To safely call an optional method, a runtime check should be performed to make sure the receiver implements the method.

This is a special compiler recognized attribute, it has several requirements, which all will be enforced by the compiler:

• The attribute can only be attached to methods which have Objective-C linkage. That is, a method inside an interface declared as extern (Objective-C)
• It can only be used for methods that are declared inside an interface
• It can only be used once in a method declaration
• It cannot be attached to a method that is a template

Examples:

import core.attribute : optional, selector;

extern (Objective-C):

struct objc_selector;
alias SEL = objc_selector*;

SEL sel_registerName(in char* str);

extern class NSObject
{
    bool respondsToSelector(SEL sel) @selector("respondsToSelector:");
}

interface Foo
{
    @optional void foo() @selector("foo");
    @optional void bar() @selector("bar");
}

class Bar : NSObject
{
    static Bar alloc() @selector("alloc");
    Bar init() @selector("init");

    void bar() @selector("bar")
    {
    }
}

extern (D) void main()
{
    auto bar = Bar.alloc.init;

    if (bar.respondsToSelector(sel_registerName("bar")))
        bar.bar();
}

struct gnuAbiTag;

Use this attribute to declare an ABI tag on a C++ symbol.

ABI tag is an attribute introduced by the GNU C++ compiler. It modifies the mangled name of the symbol to incorporate the tag name, in order to distinguish from an earlier version with a different ABI.

This is a special compiler recognized attribute, it has a few requirements, which all will be enforced by the compiler:

• There can only be one such attribute per symbol.
,
• The attribute can only be attached to an extern(C++) symbol (struct, class, enum, function, and their templated counterparts).
,
• The attribute cannot be applied to C++ namespaces. This is to prevent confusion with the C++ semantic, which allows it to be applied to namespaces.
,
• The string arguments must only contain valid characters for C++ name mangling which currently include alphanumerics and the underscore character.
,

This UDA is not transitive, and inner scope do not inherit outer scopes' ABI tag. See examples below for how to translate a C++ declaration to D. Also note that entries in this UDA will be automatically sorted alphabetically, hence gnuAbiTag("c", "b", "a") will appear as @gnuAbiTag("a", "b", "c").

See Also:

Itanium ABI spec GCC attributes documentation.

Examples:

// ---- foo.cpp
struct [[gnu::abi_tag ("tag1", "tag2")]] Tagged1_2
{
    struct [[gnu::abi_tag ("tag3")]] Tagged3
    {
        [[gnu::abi_tag ("tag4")]]
        int Tagged4 () { return 42; }
    }
}
Tagged1_2 inst1;
// ---- foo.d
@gnuAbiTag("tag1", "tag2") struct Tagged1_2
{
    // Notice the repetition
    @gnuAbiTag("tag1", "tag2", "tag3") struct Tagged3
    {
        @gnuAbiTag("tag1", "tag2", "tag3", "tag4") int Tagged4 ();
    }
}
extern __gshared Tagged1_2 inst1;