From 11e1a6f969dc0b255dd7aed12509484cf7c7ed60 Mon Sep 17 00:00:00 2001 From: Amar Takhar Date: Mon, 18 Jan 2016 00:06:41 -0500 Subject: Remove ada_user document. We are going to make Ada a chapter in the c_user manual to simplify things. Talked it over with Joel the differences between ada_user and c_users are a lot smaller than they used to be. A simple few page chapter will be enough for anyone to know the differences and will be a lot easier to maintain. --- ada_user/linker_sets.rst | 447 ----------------------------------------------- 1 file changed, 447 deletions(-) delete mode 100644 ada_user/linker_sets.rst (limited to 'ada_user/linker_sets.rst') diff --git a/ada_user/linker_sets.rst b/ada_user/linker_sets.rst deleted file mode 100644 index d314758..0000000 --- a/ada_user/linker_sets.rst +++ /dev/null @@ -1,447 +0,0 @@ -Linker Sets -########### - -.. index:: linkersets - -Introduction -============ - -Linker sets are a flexible means to create arrays of items out of a set of -object files at link-time. For example its possible to define an item *I* -of type *T* in object file *A* and an item *J* of type *T* -in object file *B* to be a member of a linker set *S*. The linker -will then collect these two items *I* and *J* and place them in -consecutive memory locations, so that they can be accessed like a normal array -defined in one object file. The size of a linker set is defined by its begin -and end markers. A linker set may be empty. It should only contain items of -the same type. - -The following macros are provided to create, populate and use linker sets. - -- ``RTEMS_LINKER_SET_BEGIN`` - Designator of the linker set begin marker - -- ``RTEMS_LINKER_SET_END`` - Designator of the linker set end marker - -- ``RTEMS_LINKER_SET_SIZE`` - The linker set size in characters - -- ``RTEMS_LINKER_ROSET_DECLARE`` - Declares a read-only linker set - -- ``RTEMS_LINKER_ROSET`` - Defines a read-only linker set - -- ``RTEMS_LINKER_ROSET_ITEM_DECLARE`` - Declares a read-only linker set item - -- ``RTEMS_LINKER_ROSET_ITEM_REFERENCE`` - References a read-only linker set item - -- ``RTEMS_LINKER_ROSET_ITEM`` - Defines a read-only linker set item - -- ``RTEMS_LINKER_ROSET_ITEM_ORDERED`` - Defines an ordered read-only linker set item - -- ``RTEMS_LINKER_RWSET_DECLARE`` - Declares a read-write linker set - -- ``RTEMS_LINKER_RWSET`` - Defines a read-write linker set - -- ``RTEMS_LINKER_RWSET_ITEM_DECLARE`` - Declares a read-write linker set item - -- ``RTEMS_LINKER_RWSET_ITEM_REFERENCE`` - References a read-write linker set item - -- ``RTEMS_LINKER_RWSET_ITEM`` - Defines a read-write linker set item - -- ``RTEMS_LINKER_RWSET_ITEM_ORDERED`` - Defines an ordered read-write linker set item - -Background -========== - -Linker sets are used not only in RTEMS, but also for example in Linux, in -FreeBSD, for the GNU C constructor extension and for global C++ constructors. -They provide a space efficient and flexible means to initialize modules. A -linker set consists of - -- dedicated input sections for the linker (e.g. ``.ctors`` and``.ctors.*`` in the case of global constructors), - -- a begin marker (e.g. provided by ``crtbegin.o``, and - -- an end marker (e.g. provided by ``ctrend.o``). - -A module may place a certain data item into the dedicated input section. The -linker will collect all such data items in this section and creates a begin and -end marker. The initialization code can then use the begin and end markers to -find all the collected data items (e.g. pointers to initialization functions). - -In the linker command file of the GNU linker we need the following output -section descriptions. -.. code:: c - - /* To be placed in a read-only memory region \*/ - .rtemsroset : { - KEEP (\*(SORT(.rtemsroset.*))) - } - /* To be placed in a read-write memory region \*/ - .rtemsrwset : { - KEEP (\*(SORT(.rtemsrwset.*))) - } - -The ``KEEP()`` ensures that a garbage collection by the linker will not -discard the content of this section. This would normally be the case since the -linker set items are not referenced directly. The ``SORT()`` directive -sorts the input sections lexicographically. Please note the lexicographical -order of the ``.begin``, ``.content`` and ``.end`` section name parts -in the RTEMS linker sets macros which ensures that the position of the begin -and end markers are right. - -So, what is the benefit of using linker sets to initialize modules? It can be -used to initialize and include only those RTEMS managers and other components -which are used by the application. For example, in case an application uses -message queues, it must call ``rtems_message_queue_create()``. In the -module implementing this function, we can place a linker set item and register -the message queue handler constructor. Otherwise, in case the application does -not use message queues, there will be no reference to the``rtems_message_queue_create()`` function and the constructor is not -registered, thus nothing of the message queue handler will be in the final -executable. - -For an example see test program :file:`sptests/splinkersets01`. - -Directives -========== - -RTEMS_LINKER_SET_BEGIN - Designator of the linker set begin marker ------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_SET_BEGIN - -.. code:: c - - volatile type \*begin = RTEMS_LINKER_SET_BEGIN( set ); - -**DESCRIPTION:** - -This macro generates the designator of the begin marker of the linker set -identified by ``set``. The item at the begin marker address is the first -member of the linker set if it exists, e.g. the linker set is not empty. A -linker set is empty, if and only if the begin and end markers have the same -address. -The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. - -RTEMS_LINKER_SET_END - Designator of the linker set end marker --------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_SET_END - -.. code:: c - - volatile type \*end = RTEMS_LINKER_SET_END( set ); - -**DESCRIPTION:** - -This macro generates the designator of the end marker of the linker set -identified by ``set``. The item at the end marker address is not a member -of the linker set. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. - -RTEMS_LINKER_SET_SIZE - The linker set size in characters ---------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_SET_SIZE - -.. code:: c - - size_t size = RTEMS_LINKER_SET_SIZE( set ); - -**DESCRIPTION:** - -This macro returns the size of the linker set identified by ``set`` in -characters. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. - -RTEMS_LINKER_ROSET_DECLARE - Declares a read-only linker set ------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET_DECLARE - -.. code:: c - - RTEMS_LINKER_ROSET_DECLARE( set, type ); - -**DESCRIPTION:** - -This macro generates declarations for the begin and end markers of a read-only -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. - -RTEMS_LINKER_ROSET - Defines a read-only linker set ---------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET - -.. code:: c - - RTEMS_LINKER_ROSET( set, type ); - -**DESCRIPTION:** - -This macro generates definitions for the begin and end markers of a read-only -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. - -RTEMS_LINKER_ROSET_ITEM_DECLARE - Declares a read-only linker set item ----------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET_ITEM_DECLARE - -.. code:: c - - RTEMS_LINKER_ROSET_ITEM_DECLARE( set, type, item ); - -**DESCRIPTION:** - -This macro generates a declaration of an item contained in the read-only linker -set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_ROSET_ITEM_REFERENCE - References a read-only linker set item --------------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET_ITEM_REFERENCE - -.. code:: c - - RTEMS_LINKER_ROSET_ITEM_REFERENCE( set, type, item ); - -**DESCRIPTION:** - -This macro generates a reference to an item contained in the read-only linker set -identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_ROSET_ITEM - Defines a read-only linker set item -------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET_ITEM - -.. code:: c - - RTEMS_LINKER_ROSET_ITEM( set, type, item ); - -**DESCRIPTION:** - -This macro generates a definition of an item contained in the read-only linker set -identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_ROSET_ITEM_ORDERED - Defines an ordered read-only linker set item ------------------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_ROSET_ITEM_ORDERED - -.. code:: c - - RTEMS_LINKER_ROSET_ITEM_ORDERED( set, type, item, order ); - -**DESCRIPTION:** - -This macro generates a definition of an ordered item contained in the read-only -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. -The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. The ``order`` parameter must be a valid linker input section name part on -which macro expansion is performed. The items are lexicographically ordered -according to the ``order`` parameter within a linker set. Ordered items are -placed before unordered items in the linker set. - -**NOTES:** - -To be resilient to typos in the order parameter, it is recommended to use the -following construct in macros defining items for a particular linker set (see -enum in ``XYZ_ITEM()``). -.. code:: c - - #include - typedef struct { - int foo; - } xyz_item; - /* The XYZ-order defines \*/ - #define XYZ_ORDER_FIRST 0x00001000 - #define XYZ_ORDER_AND_SO_ON 0x00002000 - /* Defines an ordered XYZ-item \*/ - #define XYZ_ITEM( item, order ) \\ - enum { xyz_##item = order - order }; \\ - RTEMS_LINKER_ROSET_ITEM_ORDERED( \\ - xyz, const xyz_item \*, item, order \\ - ) = { &item } - /* Example item \*/ - static const xyz_item some_item = { 123 }; - XYZ_ITEM( some_item, XYZ_ORDER_FIRST ); - -RTEMS_LINKER_RWSET_DECLARE - Declares a read-write linker set -------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET_DECLARE - -.. code:: c - - RTEMS_LINKER_RWSET_DECLARE( set, type ); - -**DESCRIPTION:** - -This macro generates declarations for the begin and end markers of a read-write -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. - -RTEMS_LINKER_RWSET - Defines a read-write linker set ----------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET - -.. code:: c - - RTEMS_LINKER_RWSET( set, type ); - -**DESCRIPTION:** - -This macro generates definitions for the begin and end markers of a read-write -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. - -RTEMS_LINKER_RWSET_ITEM_DECLARE - Declares a read-write linker set item ------------------------------------------------------------------------ - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET_ITEM_DECLARE - -.. code:: c - - RTEMS_LINKER_RWSET_ITEM_DECLARE( set, type, item ); - -**DESCRIPTION:** - -This macro generates a declaration of an item contained in the read-write linker -set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_RWSET_ITEM_REFERENCE - References a read-write linker set item ---------------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET_ITEM_REFERENCE - -.. code:: c - - RTEMS_LINKER_RWSET_ITEM_REFERENCE( set, type, item ); - -**DESCRIPTION:** - -This macro generates a reference to an item contained in the read-write linker set -identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_RWSET_ITEM - Defines a read-write linker set item --------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET_ITEM - -.. code:: c - - RTEMS_LINKER_RWSET_ITEM( set, type, item ); - -**DESCRIPTION:** - -This macro generates a definition of an item contained in the read-write linker set -identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. - -RTEMS_LINKER_RWSET_ITEM_ORDERED - Defines an ordered read-write linker set item -------------------------------------------------------------------------------- - -**CALLING SEQUENCE:** - -.. index:: RTEMS_LINKER_RWSET_ITEM_ORDERED - -.. code:: c - - RTEMS_LINKER_RWSET_ITEM_ORDERED( set, type, item, order ); - -**DESCRIPTION:** - -This macro generates a definition of an ordered item contained in the read-write -linker set identified by ``set``. The ``set`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies the linker set. The ``type`` parameter defines the type of the linker set items. The type -must be the same for all macro invocations of a particular linker set. -The ``item`` parameter itself must be a valid C designator on which no macro -expansion is performed. It uniquely identifies an item in the linker set. The ``order`` parameter must be a valid linker input section name part on -which macro expansion is performed. The items are lexicographically ordered -according to the ``order`` parameter within a linker set. Ordered items are -placed before unordered items in the linker set. - -**NOTES:** - -To be resilient to typos in the order parameter, it is recommended to use the -following construct in macros defining items for a particular linker set (see -enum in ``XYZ_ITEM()``). -.. code:: c - - #include - typedef struct { - int foo; - } xyz_item; - /* The XYZ-order defines \*/ - #define XYZ_ORDER_FIRST 0x00001000 - #define XYZ_ORDER_AND_SO_ON 0x00002000 - /* Defines an ordered XYZ-item \*/ - #define XYZ_ITEM( item, order ) \\ - enum { xyz_##item = order - order }; \\ - RTEMS_LINKER_RWSET_ITEM_ORDERED( \\ - xyz, const xyz_item \*, item, order \\ - ) = { &item } - /* Example item \*/ - static const xyz_item some_item = { 123 }; - XYZ_ITEM( some_item, XYZ_ORDER_FIRST ); - -.. COMMENT: COPYRIGHT (c) 1989-2014. - -.. COMMENT: On-Line Applications Research Corporation (OAR). - -.. COMMENT: All rights reserved. - -- cgit v1.2.3