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>cdl_component</TITLE
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COLSPAN="3"
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>The <SPAN
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CLASS="APPLICATION"
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>eCos</SPAN
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> Component Writer's Guide</TH
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><HR
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WIDTH="100%"></DIV
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><H1
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><A
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NAME="REF.CDL-COMPONENT"><TT
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CLASS="LITERAL"
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>cdl_component</TT
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></H1
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><DIV
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CLASS="REFNAMEDIV"
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><A
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NAME="AEN3091"
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></A
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><H2
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>Name</H2
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>Command <TT
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CLASS="LITERAL"
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>cdl_component</TT
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>&nbsp;--&nbsp;Define a component, a collection of configuration options</DIV
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><DIV
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CLASS="REFSYNOPSISDIV"
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><A
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NAME="AEN3095"><H2
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>Synopsis</H2
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><TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="SYNOPSIS"
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>cdl_component &lt;name&gt; {
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    &#8230;
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}</PRE
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></TD
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></TR
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></TABLE
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN3097"
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></A
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><H2
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>Description</H2
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><P
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>A component is a configuration option that can contain additional
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options and sub-components. The body of a <TT
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CLASS="LITERAL"
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>cdl_component</TT
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> can contain
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the same properties as that of a <TT
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CLASS="LITERAL"
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>cdl_option</TT
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>. There is an additional
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property, <SPAN
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CLASS="PROPERTY"
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>script</SPAN
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> which allows configuration data to be split into
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multiple files. It is also possible for a component body to include
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<TT
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CLASS="LITERAL"
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>cdl_component</TT
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>, <TT
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CLASS="LITERAL"
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>cdl_option</TT
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> and <TT
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CLASS="LITERAL"
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>cdl_interface</TT
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> entities that should
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go below this component in the configuration hierarchy.</P
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><P
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><TT
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CLASS="LITERAL"
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>cdl_component</TT
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> is implemented as a Tcl command that takes two
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arguments, a name and a body. The name must be a valid C preprocessor
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identifier: a sequence of upper or lower case letters, digits or
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underscores, starting with a non-digit character; identifiers
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beginning with an underscore should normally be avoided because they
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may clash with system packages or with identifiers reserved for use by
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the compiler. Within a single configuration, names must be unique. If
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a configuration contained two packages which defined the same entity
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<TT
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CLASS="LITERAL"
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>CYGIMP_SOME_OPTION</TT
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>, any references to that entity
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in a <SPAN
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CLASS="PROPERTY"
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>requires</SPAN
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> property or any other expression would be ambiguous.
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It is possible for a given name to be used by two different packages
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if those packages should never be loaded into a single configuration.
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For example, architectural HAL packages are allowed to re-use certain
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names because a single configuration cannot target two different
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architectures. For a recommended naming convention see <A
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HREF="package.contents.html"
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>the Section called <I
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>Package Contents and Layout</I
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> in Chapter 2</A
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>.</P
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><P
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>The second argument to <TT
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CLASS="LITERAL"
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>cdl_component</TT
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> is a body of properties and
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other commands, typically surrounded by braces so that the Tcl
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interpreter treats it as a single argument. This body will be
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processed by a recursive invocation of the Tcl interpreter, extended
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with additional commands for the various properties that are allowed
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inside a <TT
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CLASS="LITERAL"
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>cdl_component</TT
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>. The valid commands are:</P
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><P
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></P
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><DIV
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CLASS="VARIABLELIST"
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><DL
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><DT
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><A
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HREF="ref.active-if.html"
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><SPAN
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CLASS="PROPERTY"
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>active_if</SPAN
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></A
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></DT
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><DD
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><P
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>Allow additional control over the active state of this component.</P
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></DD
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><DT
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><A
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HREF="ref.calculated.html"
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><SPAN
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CLASS="PROPERTY"
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>calculated</SPAN
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></A
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></DT
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><DD
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><P
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>The component's value is not directly user-modifiable, it is calculated
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using a suitable CDL expression.</P
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></DD
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><DT
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><A
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HREF="ref.cdl-component.html"
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><TT
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CLASS="LITERAL"
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>cdl_component</TT
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></A
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></DT
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><DD
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><P
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>Define a sub-component.</P
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></DD
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><DT
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><A
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HREF="ref.cdl-interface.html"
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><TT
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CLASS="LITERAL"
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>cdl_interface</TT
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></A
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></DT
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><DD
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><P
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>Define an interface which should appear immediately below this
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component in the configuration hierarchy.</P
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></DD
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><DT
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><A
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HREF="ref.cdl-option.html"
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><TT
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CLASS="LITERAL"
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>cdl_option</TT
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></A
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></DT
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><DD
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><P
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>Define a configuration option which should appear immediately below
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this component in the configuration hierarchy.</P
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></DD
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><DT
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><A
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HREF="ref.compile.html"
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><SPAN
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CLASS="PROPERTY"
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>compile</SPAN
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></A
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></DT
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><DD
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><P
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>List the source files that should be built if this component is active
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and enabled.</P
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></DD
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><DT
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><A
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HREF="ref.default-value.html"
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><SPAN
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CLASS="PROPERTY"
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>default_value</SPAN
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></A
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></DT
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><DD
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><P
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>Provide a default value for this component using a CDL expression.</P
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></DD
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><DT
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><A
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HREF="ref.define.html"
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><SPAN
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CLASS="PROPERTY"
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>define</SPAN
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></A
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></DT
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><DD
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><P
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>Specify additional <TT
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CLASS="LITERAL"
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>#define</TT
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> symbols that should go
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into the owning package's configuration header file.</P
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></DD
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><DT
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><A
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HREF="ref.define-format.html"
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><SPAN
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CLASS="PROPERTY"
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>define_format</SPAN
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></A
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></DT
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><DD
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><P
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>Control how the component's value will appear in the configuration header
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file.</P
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></DD
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><DT
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><A
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HREF="ref.define-proc.html"
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><SPAN
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CLASS="PROPERTY"
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>define_proc</SPAN
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></A
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></DT
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><DD
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><P
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>Use a fragment of Tcl code to output additional data to
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configuration header files.</P
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></DD
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><DT
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><A
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HREF="ref.description.html"
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><SPAN
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CLASS="PROPERTY"
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>description</SPAN
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></A
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></DT
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><DD
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><P
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>Provide a textual description for this component.</P
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></DD
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><DT
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><A
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HREF="ref.display.html"
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><SPAN
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CLASS="PROPERTY"
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>display</SPAN
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></A
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></DT
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><DD
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><P
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>Provide a short string describing this component.</P
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></DD
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><DT
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><A
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HREF="ref.doc.html"
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><SPAN
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CLASS="PROPERTY"
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>doc</SPAN
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></A
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></DT
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><DD
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><P
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>The location of on-line documentation for this component.</P
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></DD
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><DT
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><A
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HREF="ref.flavor.html"
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><SPAN
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CLASS="PROPERTY"
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>flavor</SPAN
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></A
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></DT
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><DD
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><P
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>Specify the nature of this component.</P
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></DD
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><DT
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><A
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HREF="ref.if-define.html"
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><SPAN
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CLASS="PROPERTY"
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>if_define</SPAN
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></A
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></DT
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><DD
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><P
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>Output a common preprocessor construct to a configuration header file. </P
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></DD
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><DT
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><A
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HREF="ref.implements.html"
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><SPAN
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CLASS="PROPERTY"
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>implements</SPAN
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></A
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></DT
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><DD
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><P
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>Enabling this component provides one instance of a more general
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interface. </P
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></DD
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><DT
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><A
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HREF="ref.legal-values.html"
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><SPAN
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CLASS="PROPERTY"
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>legal_values</SPAN
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></A
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></DT
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><DD
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><P
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>Impose constraints on the possible values for this component.</P
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></DD
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><DT
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><A
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HREF="ref.make.html"
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><SPAN
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CLASS="PROPERTY"
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>make</SPAN
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></A
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></DT
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><DD
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><P
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>An additional custom build step associated with this component, resulting
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in a target that should not go directly into a library.</P
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></DD
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><DT
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><A
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HREF="ref.make-object.html"
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><SPAN
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CLASS="PROPERTY"
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>make_object</SPAN
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></A
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></DT
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><DD
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><P
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>An additional custom build step associated with this component, resulting
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in an object file that should go into a library.</P
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></DD
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><DT
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><A
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HREF="ref.no-define.html"
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><SPAN
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CLASS="PROPERTY"
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>no_define</SPAN
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></A
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></DT
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><DD
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><P
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>Suppress the normal generation of a preprocessor
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<TT
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CLASS="LITERAL"
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>#define</TT
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> symbol in a configuration header file.</P
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></DD
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><DT
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><A
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HREF="ref.parent.html"
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><SPAN
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CLASS="PROPERTY"
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>parent</SPAN
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></A
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></DT
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><DD
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><P
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>Control the location of this component in the configuration hierarchy. </P
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></DD
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><DT
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><A
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HREF="ref.requires.html"
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><SPAN
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CLASS="PROPERTY"
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>requires</SPAN
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></A
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></DT
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><DD
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><P
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>List constraints that the configuration should satisfy if this component is
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active and enabled.</P
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></DD
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><DT
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><A
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HREF="ref.script.html"
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><SPAN
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CLASS="PROPERTY"
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>script</SPAN
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></A
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></DT
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><DD
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><P
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>Include additional configuration information from another
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CDL script</P
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></DD
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></DL
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></DIV
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN3255"
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></A
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><H2
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>Example</H2
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><P
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><TABLE
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BORDER="5"
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BGCOLOR="#E0E0F0"
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WIDTH="70%"
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><TR
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><TD
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><PRE
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CLASS="PROGRAMLISTING"
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>cdl_component CYGDBG_USE_ASSERTS {
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    display       "Use asserts"
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    default_value 1
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    description   "
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        If this component is enabled, assertions in the code are
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        tested at run-time. Assert functions (CYG_ASSERT()) are
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        defined in 'include/cyg/infra/cyg_ass.h' within the 'install'
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        tree. If the component is disabled, these result in no
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        additional object code and no checking of the asserted
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        conditions."
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    script        assert.cdl
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}</PRE
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></TD
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></TR
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></TABLE
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></P
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></DIV
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><DIV
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CLASS="REFSECT1"
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><A
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NAME="AEN3259"
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></A
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><H2
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>See Also</H2
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><P
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>Command <A
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HREF="ref.cdl-option.html"
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><TT
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CLASS="LITERAL"
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>cdl_option</TT
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></A
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>,
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command <A
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HREF="ref.cdl-package.html"
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><TT
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CLASS="LITERAL"
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>cdl_package</TT
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></A
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>,
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command <A
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HREF="ref.cdl-interface.html"
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><TT
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CLASS="LITERAL"
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>cdl_interface</TT
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></A
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>.</P
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></DIV
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><DIV
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><HR
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WIDTH="100%"><TABLE
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SUMMARY="Footer navigation table"
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><A
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HREF="ref.cdl-option.html"
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ACCESSKEY="P"
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>Prev</A
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></TD
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><TD
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WIDTH="34%"
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ALIGN="center"
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><A
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HREF="cdl-guide.html"
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>Home</A
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></TD
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>Next</A
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><TR
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><TD
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WIDTH="33%"
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ALIGN="left"
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VALIGN="top"
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><TT
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CLASS="LITERAL"
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>cdl_option</TT
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></TD
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ALIGN="center"
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VALIGN="top"
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><A
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><TT
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