[thirdparty/gcc.git] / gcc / doc / gccint / memory-management-and-type-information / marking-roots-for-the-garbage-collector.rst

..
  Copyright 1988-2022 Free Software Foundation, Inc.
  This is part of the GCC manual.
  For copying conditions, see the copyright.rst file.

.. index:: roots, marking, marking roots

.. _ggc-roots:

Marking Roots for the Garbage Collector
***************************************

In addition to keeping track of types, the type machinery also locates
the global variables (:dfn:`roots`) that the garbage collector starts
at.  Roots must be declared using one of the following syntaxes:

* ``extern GTY(([options])) typename;``

* ``static GTY(([options])) typename;``

The syntax

* ``GTY(([options])) typename;``

is *not* accepted.  There should be an ``extern`` declaration
of such a variable in a header somewhere---mark that, not the
definition.  Or, if the variable is only used in one file, make it
``static``.
Commit	Line	Data
c63539ff ML	1	..
	2	Copyright 1988-2022 Free Software Foundation, Inc.
	3	This is part of the GCC manual.
	4	For copying conditions, see the copyright.rst file.
	5
	6	.. index:: roots, marking, marking roots
	7
	8	.. _ggc-roots:
	9
	10	Marking Roots for the Garbage Collector
	11	***************************************
	12
	13	In addition to keeping track of types, the type machinery also locates
	14	the global variables (:dfn:`roots`) that the garbage collector starts
	15	at. Roots must be declared using one of the following syntaxes:
	16
	17	* ``extern GTY(([options])) typename;``
	18
	19	* ``static GTY(([options])) typename;``
	20
	21	The syntax
	22
	23	* ``GTY(([options])) typename;``
	24
	25	is not accepted. There should be an ``extern`` declaration
	26	of such a variable in a header somewhere---mark that, not the
	27	definition. Or, if the variable is only used in one file, make it
3ed1b4ce	28	``static``.