+++ /dev/null
-<!-- Copyright (C) 2003 Red Hat, Inc. -->
-<!-- This material may be distributed only subject to the terms -->
-<!-- and conditions set forth in the Open Publication License, v1.0 -->
-<!-- or later (the latest version is presently available at -->
-<!-- http://www.opencontent.org/openpub/). -->
-<!-- Distribution of the work or derivative of the work in any -->
-<!-- standard (paper) book form is prohibited unless prior -->
-<!-- permission is obtained from the copyright holder. -->
-<HTML
-><HEAD
-><TITLE
->if_define</TITLE
-><meta name="MSSmartTagsPreventParsing" content="TRUE">
-<META
-NAME="GENERATOR"
-CONTENT="Modular DocBook HTML Stylesheet Version 1.76b+
-"><LINK
-REL="HOME"
-TITLE="The eCos Component Writer's Guide"
-HREF="cdl-guide.html"><LINK
-REL="UP"
-TITLE="CDL Language Specification"
-HREF="reference.html"><LINK
-REL="PREVIOUS"
-TITLE="hardware"
-HREF="ref.hardware.html"><LINK
-REL="NEXT"
-TITLE="implements"
-HREF="ref.implements.html"></HEAD
-><BODY
-CLASS="REFENTRY"
-BGCOLOR="#FFFFFF"
-TEXT="#000000"
-LINK="#0000FF"
-VLINK="#840084"
-ALINK="#0000FF"
-><DIV
-CLASS="NAVHEADER"
-><TABLE
-SUMMARY="Header navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TH
-COLSPAN="3"
-ALIGN="center"
->The <SPAN
-CLASS="APPLICATION"
->eCos</SPAN
-> Component Writer's Guide</TH
-></TR
-><TR
-><TD
-WIDTH="10%"
-ALIGN="left"
-VALIGN="bottom"
-><A
-HREF="ref.hardware.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="80%"
-ALIGN="center"
-VALIGN="bottom"
-></TD
-><TD
-WIDTH="10%"
-ALIGN="right"
-VALIGN="bottom"
-><A
-HREF="ref.implements.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-></TABLE
-><HR
-ALIGN="LEFT"
-WIDTH="100%"></DIV
-><H1
-><A
-NAME="REF.IF-DEFINE"><SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-></H1
-><DIV
-CLASS="REFNAMEDIV"
-><A
-NAME="AEN4442"
-></A
-><H2
->Name</H2
->Property <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> -- Output a common preprocessor construct to a configuration
-header file.</DIV
-><DIV
-CLASS="REFSYNOPSISDIV"
-><A
-NAME="AEN4446"><H2
->Synopsis</H2
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="SYNOPSIS"
->cdl_option <name> {
- if_define [-file=<filename>] <symbol1> <symbol2>
- …
-}</PRE
-></TD
-></TR
-></TABLE
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN4448"
-></A
-><H2
->Description</H2
-><P
->The purpose of the <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> property is best explained by an
-example. Suppose you want finer-grained control over assertions, say
-on a per-package or even a per-file basis rather than globally. The
-assertion macros can be defined by an exported header file in an
-infrastructure package, using code like the following:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#ifdef CYGDBG_USE_ASSERTS
-# define CYG_ASSERT( _bool_, _msg_ ) \
- CYG_MACRO_START \
- if ( ! ( _bool_ ) ) \
- CYG_ASSERT_DOCALL( _msg_ ); \
- CYG_MACRO_END
-#else
-# define CYG_ASSERT( _bool_, _msg_ ) CYG_EMPTY_STATEMENT
-#endif</PRE
-></TD
-></TR
-></TABLE
-><P
->Assuming this header file is <TT
-CLASS="LITERAL"
->#include'd</TT
-> directly or
-indirectly by any code which may need to be built with assertions
-enabled, the challenge is now to control whether or not
-<TT
-CLASS="VARNAME"
->CYGDBG_USE_ASSERTS</TT
-> is defined for any given source
-file. This is the purpose of the <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> property:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->cdl_option CYGDBG_KERNEL_USE_ASSERTS {
- …
- if_define CYGSRC_KERNEL CYGDBG_USE_ASSERTS
- requires CYGDBG_INFRA_ASSERTION_SUPPORT
-}</PRE
-></TD
-></TR
-></TABLE
-><P
->If this option is active and enabled then the kernel's configuration
-header file would end up containing the following:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#ifdef CYGSRC_KERNEL
-# define CYGDBG_USE_ASSERTS 1
-#endif</PRE
-></TD
-></TR
-></TABLE
-><P
->Kernel source code can now begin with the following construct:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGSRC_KERNEL 1
-#include <pkgconf/kernel.h>
-#include <cyg/infra/cyg_ass.h></PRE
-></TD
-></TR
-></TABLE
-><P
->The configuration option only affects kernel source code, assuming
-nothing else <TT
-CLASS="LITERAL"
->#define's</TT
-> the symbol
-<TT
-CLASS="VARNAME"
->CYGSRC_KERNEL</TT
->. If the per-package assertion option
-is disabled then <TT
-CLASS="VARNAME"
->CYGDBG_USE_ASSERTS</TT
-> will not get
-defined. If the option is enabled then
-<TT
-CLASS="VARNAME"
->CYGDBG_USE_ASSERTS</TT
-> will get defined and assertions
-will be enabled for the kernel sources. It is possible to use the same
-mechanism for other facilities such as tracing, and to apply it at a
-finer grain such as individual source files by having multiple options
-with <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> properties and multiple symbols such as
-<TT
-CLASS="VARNAME"
->CYGSRC_KERNEL_SCHED_BITMAP_CXX</TT
->.</P
-><P
->The <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> property takes two arguments, both of which must be
-valid C preprocessor symbols. If the current option is active and
-enabled then three lines will be output to the configuration header
-file:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#ifdef <symbol1>
-# define <symbol2>
-#endif</PRE
-></TD
-></TR
-></TABLE
-><P
->If the option is inactive or disabled then these lines will not be
-output. By default the current package's configuration header file
-will be used, but it is possible to specify an alternative destination
-using a <TT
-CLASS="LITERAL"
->-file</TT
-> option. At present the only
-legitimate alternative destination is <TT
-CLASS="LITERAL"
->system.h</TT
->, the
-global configuration header. <SPAN
-CLASS="PROPERTY"
->if_define</SPAN
-> processing happens in
-addition to, not instead of, the normal <TT
-CLASS="LITERAL"
->#define</TT
->
-processing or the handling of other header-file related properties.</P
-><DIV
-CLASS="NOTE"
-><BLOCKQUOTE
-CLASS="NOTE"
-><P
-><B
->Note: </B
->The infrastructure in the current <SPAN
-CLASS="APPLICATION"
->eCos</SPAN
-> release does not yet work
-this way. In future it may do so, and the intention is that suitable
-configuration options get generated semi-automatically by the
-configuration system rather than having to be defined explicitly.</P
-></BLOCKQUOTE
-></DIV
-><DIV
-CLASS="TIP"
-><BLOCKQUOTE
-CLASS="TIP"
-><P
-><B
->Tip: </B
->As an alternative to changing the configuration, updating the build
-tree, and so on, it is possible to enable assertions by editing a
-source file directly, for example:</P
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->#define CYGSRC_KERNEL 1
-#define CYGDBG_USE_ASSERTS 1
-#include <pkgconf/kernel.h>
-#include <cyg/infra/cyg_ass.h></PRE
-></TD
-></TR
-></TABLE
-><P
->The assertion header file does not care whether
-<TT
-CLASS="VARNAME"
->CYGDBG_USE_ASSERTS</TT
-> is <TT
-CLASS="LITERAL"
->#define'd</TT
->
-via a configuration option or by explicit code. This technique can be
-useful to component writers when debugging their source code, although
-care has to be taken to remove any such <TT
-CLASS="LITERAL"
->#define's</TT
->
-later on.</P
-></BLOCKQUOTE
-></DIV
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN4487"
-></A
-><H2
->Example</H2
-><TABLE
-BORDER="5"
-BGCOLOR="#E0E0F0"
-WIDTH="70%"
-><TR
-><TD
-><PRE
-CLASS="PROGRAMLISTING"
->cdl_option CYGDBG_KERNEL_USE_ASSERTS {
- display "Assertions in the kernel package"
- …
- if_define CYGSRC_KERNEL CYGDBG_USE_ASSERTS
- requires CYGDBG_INFRA_ASSERTION_SUPPORT
-}</PRE
-></TD
-></TR
-></TABLE
-></DIV
-><DIV
-CLASS="REFSECT1"
-><A
-NAME="AEN4490"
-></A
-><H2
->See Also</H2
-><P
->Properties <A
-HREF="ref.define.html"
-><SPAN
-CLASS="PROPERTY"
->define</SPAN
-></A
->,
-<A
-HREF="ref.define-format.html"
-><SPAN
-CLASS="PROPERTY"
->define_format</SPAN
-></A
->,
-<A
-HREF="ref.define-header.html"
-><SPAN
-CLASS="PROPERTY"
->define_header</SPAN
-></A
->,
-<A
-HREF="ref.define-proc.html"
-><SPAN
-CLASS="PROPERTY"
->define_proc</SPAN
-></A
-> and
-<A
-HREF="ref.no-define.html"
-><SPAN
-CLASS="PROPERTY"
->no_define</SPAN
-></A
->.</P
-></DIV
-><DIV
-CLASS="NAVFOOTER"
-><HR
-ALIGN="LEFT"
-WIDTH="100%"><TABLE
-SUMMARY="Footer navigation table"
-WIDTH="100%"
-BORDER="0"
-CELLPADDING="0"
-CELLSPACING="0"
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
-><A
-HREF="ref.hardware.html"
-ACCESSKEY="P"
->Prev</A
-></TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="cdl-guide.html"
-ACCESSKEY="H"
->Home</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
-><A
-HREF="ref.implements.html"
-ACCESSKEY="N"
->Next</A
-></TD
-></TR
-><TR
-><TD
-WIDTH="33%"
-ALIGN="left"
-VALIGN="top"
-><SPAN
-CLASS="PROPERTY"
->hardware</SPAN
-></TD
-><TD
-WIDTH="34%"
-ALIGN="center"
-VALIGN="top"
-><A
-HREF="reference.html"
-ACCESSKEY="U"
->Up</A
-></TD
-><TD
-WIDTH="33%"
-ALIGN="right"
-VALIGN="top"
-><SPAN
-CLASS="PROPERTY"
->implements</SPAN
-></TD
-></TR
-></TABLE
-></DIV
-></BODY
-></HTML
->
\ No newline at end of file
projects / karo-tx-redboot.git / blobdiff