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Documented the new -fconstant-string-class option.

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From-SVN: r35537
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Ovidiu Predescu 2000-08-07 06:27:47 +00:00
parent 9bc3876e69
commit 9f942e8c17
1 changed files with 59 additions and 16 deletions
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75
libobjc/objc-features.texi
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@ -5,7 +5,14 @@
@setchapternewpage odd
@c %**end of header
@node Top, Executing code before main, , (dir), (dir)
@menu
* Executing code before main::
* Type encoding::
* Garbage Collection::
* Constant string objects::
@end menu
@node Top, Executing code before main, (dir), (dir)
@comment node-name, next, previous, up
@chapter GNU Objective-C runtime features
@ -16,14 +23,8 @@ resources on the Internet that present the language. Questions and
comments about this document to Ovidiu Predescu
@code{<ovidiu@@cup.hp.com>}.
@menu
* Executing code before main::
* Type encoding::
* Garbage Collection::
@end menu
@node Executing code before main, What you can and what you cannot do in +load, Top, Top
@node Executing code before main, Type encoding, Top, Top
@section @code{+load}: Executing code before main
@ -101,14 +102,14 @@ You should be aware of its limitations when you decide to use it
instead of @code{+initialize}.
@menu
* What you can and what you cannot do in +load::
* What you can and what you cannot do in +load::
@end menu
@node What you can and what you cannot do in +load, Type encoding, Executing code before main, Executing code before main
@node What you can and what you cannot do in +load, , Executing code before main, Executing code before main
@subsection What you can and what you cannot do in @code{+load}
The +load implementation in the GNU runtime guarantees you the following
The @code{+load} implementation in the GNU runtime guarantees you the following
things:
@itemize @bullet
@ -169,7 +170,7 @@ above apply to classes defined in bundle.
@node Type encoding, Garbage Collection, What you can and what you cannot do in +load, Top
@node Type encoding, Garbage Collection, Executing code before main, Top
@section Type encoding
The Objective-C compiler generates type encodings for all the
@ -309,15 +310,13 @@ however, the type specifiers are only encoded when they appear in method
argument types.
@node Garbage Collection, , Type encoding, Top
@page
@node Garbage Collection, Constant string objects, Type encoding, Top
@section Garbage Collection
Support for a new memory management policy has been added by using a
powerful conservative garbage collector, known as the
Boehm-Demers-Weiser conservative garbage collector. It is available from
@w{@uref{http://reality.sgi.com/boehm_mti/gc.html}}.
@w{@uref{http://www.hpl.hp.com/personal/Hans_Boehm/gc/}}.
To enable the support for it you have to configure the compiler using an
additional argument, @w{@kbd{--enable-objc-gc}}. You need to have
@ -387,6 +386,50 @@ represented by the @code{'!'} character. The
specifier to the string type description of the instance variable named
as argument.
@c =========================================================================
@node Constant string objects, , Garbage Collection, Top
@comment node-name, next, previous, up
@section Constant string objects
GNU Objective-C provides constant string objects that are generated
directly by the compiler. You declare a constant string object by
prefixing a C constant string with the character @code{@@}:
@example
id myString = @@"this is a constant string object";
@end example
The constant string objects are usually instances of the
@code{NXConstantString} class which is provided by the GNU Objective-C
runtime. To get the definition of this class you must include the
@file{objc/NXConstStr.h} header file.
User defined libraries may want to implement their own constant string
class. To be able to support them, the GNU Objective-C compiler provides
a new command line options @code{-fconstant-string-class=<class
name>}. The provided class should adhere to a strict structure, the same
as @code{NXConstantString}'s structure:
@example
@@interface NXConstantString : Object
@{
char *c_string;
unsigned int len;
@}
@@end
@end example
User class libraries may choose to inherit the customized constant
string class from a different class than @code{Object}. There is no
requirement in the methods the constant string class has to implement.
When a file is compiled with the @code{-fconstant-string-class} option,
all the constant string objects will be instances of the class specified
as argument to this option. It is possible to have multiple compilation
units referring to different constant string classes, neither the
compiler nor the linker impose any restrictions in doing this.
@bye