\input texinfo @c -*-texinfo-*-
@c $Id: ctpp.texi,v 1.3 2009/01/22 01:01:17 kiesling Exp $
@c %**start of header  
@setfilename ctpp.info
@settitle @ctpp
@setchapternewpage odd
@paragraphindent 0
@c %**end of header

@set VERSION 1.0.45

@ifinfo

@dircategory Ctalk
@direntry
* ctpp: (ctpp).	      The Ctalk C preprocessor.
@end direntry

This file documents ctpp version @value{VERSION}.

Copyright @copyright{} 2005-2009  Robert Kiesling, ctalk@@ctalklang.org.

Permission is granted to copy, distribute and/or modify this document
under the terms of the GNU Free Documentation License, Version 1.1 or
any later version published by the Free Software Foundation; with no
Invariant Sections, with no Front-Cover Texts, and with no Back-Cover
Texts.  A copy of the license is included in the section entitled
``Copying.''

@end ifinfo

@titlepage
@title ctpp @value{VERSION}
@subtitle The ctalk preprocessor.
@author Robert Kiesling, rkies@@cpan.org
@end titlepage

@ifnottex

@node Top, About, (dir), (dir)
@c title, next, previous, up

@top Introduction to ctpp

This manual describes ctpp, the ctalk C preprocessor, version @value{VERSION}.


@menu
* About::          An overview of ctpp.
* Options::        Command line options.
* Include::        C header files.
* Macros::         Macro definitions and processing.
* Directives::     The macro directives that ctpp recognizes.
* Copying::        The GNU Free Documentation License.
* Index::
@end menu

@end ifnottex

@node About, Options, Top, Top

@heading About ctpp

Ctpp is the ctalk language's preprocessor.  The preprocessor follows
the C preprocessing conventions of ISO C (C99), and it also provides
extensions for compiler specific features.  At this time, ctpp
provides GNU C compatible extensions, and also extensions of its own.

The preprocessor's command line options are compatible with GNU cpp,
with the addition of options for its own extensions.  Unlike GNU cpp,
however, ctpp does not provide support for other dialects of C, like
Objective C or C++.  However, the preprocessor recognizes the command
line options for those dialects.

Ctpp attempts to comply with C99 as much as possible.  At this time,
however, the preprocessor does not provide support for macros with a
variable number of arguments, and it has been tested only with
operating system-specific implementations of the library headers and
macros described in the C99 standard.  Ctpp also does not implement
macro substitutions in #include statements.

@node Options, Include, About, Top

@heading Command Line Options
@cindex Command line options

Ctpp's command line syntax is:
@example
ctpp [options] [infile|-] [outfile|-]
@end example

The table below lists the options that ctpp recognizes.

@table @code

@cindex -$ command line option
@cindex @code{__CTPP_WARNDOLLAR_OPT__} macro
@item -$
Warn if @samp{$} is an identifier character.  This is a legacy option
because @samp{$} is commonly used in identifier names on some
operating systems.  This option defines the
@code{__CTPP_WARNDOLLAR_OPT__} built-in macro.

@cindex -A command line option
@item -A@var{predicate}[@var{value}]
Assert that macro @var{predicate} has the value @var{value}.  If 
@var{value} is omitted, it defaults to, ``1.'' 

The form @samp{-A-} undefines all predefined macros and assertions.

The preprocessor tests assertions with the @samp{#assert} directive, 
which is a GNU @command{cpp} extension. @xref{Macros}.

@cindex -ansi command line option
@item -ansi
Included for compatibility with GNU cpp.  For ctpp, it is equivalent
to the @samp{lang-c} or @samp{std=}@var{<C language standards}, given
below. 

@cindex -C command line option
@cindex @code{__CTPP_KEEPCOMMENTS_OPT__} macro
@item -C
Pass comments through to the output.  This option defines the
@code{__CTPP_KEEPCOMMENTS_OPT__} built-in macro.

@cindex -D command line option
@item -D@var{name}[=@var{definition}]
Define macro @var{name} as @var{definition}.  If @var{definition} is
omitted, it defaults to, ``1,'' so the preprocessor can test the
macro with @samp{#if} or @samp{#ifdef}.

@cindex -dD command line option
@cindex @code{__CTPP_DEFINESTOOUTPUT_OPT__} macro
@item -dD
Include preprocessor @samp{#define} statements in the output.  This
option defines the @code{__CTPP_DEFINESTOOUTPUT_OPT__} built-in macro.

@cindex -dF command line option
@cindex @code{__CTPP_DEFINESTOFILE_OPT__} macro
@item -dF @var{file}
After processing the input, write the macro defintions to @var{file}.
This option defines the @code{__CTPP_DEFINESTOFILE_OPT__} built-in macro.

@cindex -dM command line option
@cindex @code{__CTPP_DEFINESONLY_OPT__} macro
@item -dM
Instead of writing output to a file, output the macro definitions
to standard output.
This option defines the @code{__CTPP_DEFINESONLY_OPT__} built-in macro.

@cindex -dN command line option
@cindex @code{__CTPP_DEFINENAMESSONLY_OPT__} macro
@item -dN
Instead of writing output to a file, output the macro names only,
without their definitions, to standard output.
This option defines the @code{__CTPP_DEFINENAMESSONLY_OPT__} built-in macro.

@cindex -fpreprocessed command line option
@cindex @code{__CTPP_PRE_PREPROCESSED_OPT__} macro
@item -fpreprocessed
Treat the input file as already preprocessed.
This option defines the @code{__CTPP_PRE_PREPROCESSED_OPT__} built-in macro.

@cindex -gcc command line option
@cindex @code{__CTPP_GCC_MACROS_OPT__} macro
@item -gcc
On systems that use @command{gcc} as the compiler, define the macros
@samp{__GNUC__, __GNUC_MINOR,} and @samp{__GNUC_PATCHLEVEL__}.
This option defines the @code{__CTPP_GCC_MACROS_OPT__} built-in macro.
Ctpp enables this option by default.

@cindex -I command line option
@item -I @var{dir}
Search @var{dir} for files included with the @samp{#include}
directive.

@cindex -I- command line option
@item -I-
Inhibit the search of directories specified with previous @samp{-I} 
command line statements to files included with
@samp{#include"@var{file}"}, but not files included with 
@samp{#include<@var{file}>}.

Directories specified after the @samp{-I-} option with @samp{-I
@var{dir}} are searched for all included files.

@cindex -idirafter command line option
@item -idirafter @var{dir}
Include @var{dir} in the secondary include path list.

@cindex -imacros command line option
@item -imacros @var{file}
Include macro definitions from @var{file} before processing the
input file.

@cindex -iprefix command line option
@item -iprefix @var{prefix}
Use @var{prefix} as the prefix to directories specified with
@samp{-iwithprefix}. 

@cindex -isystem command line option
@item -isystem @var{dir}
Add @var{dir} to the list of system include directories to search for 
included files.  Directories specified with @samp{-isystem} are added to the 
search list after directories that are specified with the @samp{-I}
option.  

The @samp{-isystem} option is used mainly to add system include directories 
when using ctpp with non-standard compiler configurations.  The 
@samp{-nostdinc} option does not affect directories included with
@samp{-isystem}.

@cindex --lang-c++ command line option
@cindex @code{__CTPP_LANG_CPLUSPLUS_OPT__} macro
@item --lang-c++
Adds C++ library include directories to the preprocessor's include
search path.
This option defines the @code{__CTPP_LANG_CPLUSPLUS_OPT__} built-in macro.

@cindex -H command line option
@cindex @code{__CTPP_PRINT_HEADERS_OPT__} macro
@item -H
Print the paths of header files as they are included, indented to 
indicate the level of include nesting.
This option defines the @code{__CTPP_PRINT_HEADERS_OPT__} built-in macro.

@cindex -h command line option
@cindex -help command line option
@cindex --help command line option
@item -h
@item -help
@item --help
Print a help message and exit.

@cindex -M command line option
@cindex @code{__CTPP_MAKERULES_OPT__} macro
@item -M [-MG]
Instead of outputting the preprocessed source, generate to standard
output a @command{make} rule to build the source file.  @samp{-MG} 
directs the preprocessor to assume that missing header files are
generated files and exist in the same directory as the source file.
The @code{-M}@var{n} command line options define the
@code{__CTPP_MAKERULES_OPT__} built-in macro.

@cindex -MD command line option
@item -MD @var{file}
Generate a @command{make} rule, and save the rule in @var{file}.

@cindex -MM command line option
@item -MM
Generate a @command{make} rule to build the source file, but include 
header dependencies only for files included with
@samp{#include"@var{file}"}, and not @samp{#include<@var{file}>}.
@samp{-MMD @var{file}} is the same as @samp{-MM}, but ctpp writes the
make rule to @var{file} instead of standard output.

@cindex -MQ command line option
@item -MQ @var{target}
A synonym for @code{-MT}, included for compatibility with GNU cpp.
Unlike GNU cpp, ctpp does not expand or quote target expressions or
special characters.

@cindex -MT command line option
@item -MT @var{target}
Use @var{target} as the target of the make rule output by ctpp.  
If a target is not specified, it is the base name of the input
file with the extension @samp{.o}.

@cindex -move-includes command line option
@cindex @code{__CTPP_MOVEINCLUDES_OPT__} macro
@item -move-includes
Move @code{#include} preprocessor directives to the beginning
of the input before preprocessing.

The @code{-move-includes} option does not check for
conditional branches, so an @code{#include} directive can be
moved outside of a conditional clause.

This option defines the @code{__CTPP_MOVEINCLUDES_OPT__} built-in macro.

@cindex -no-gcc command line option
@item -no-gcc
On systems that use @command{gcc} as the compiler, don't define 
the macros @samp{__GNUC__, __GNUC_MINOR__}, or @samp{__GNUC_PATCHLEVEL__.}

@cindex -nostdinc command line option
@cindex @code{__CTPP_NOSTDINC_OPT__} macro
@item -nostdinc
Do not search system include directories for include files.
This option defines the @code{__CTPP_NOSTDINC_OPT__} built-in macro.

@cindex -o command line option
@item -o @var{output_file}
Write the preprocessor output to @var{output_file}.

@cindex -P command line option
@cindex @code{__CTPP_NOLINEMARKER_OPT__} macro
@item -P
Do not generate line number information in the output.
This option defines the @code{__CTPP_NOLINEMARKER_OPT__} built-in macro.

@cindex -no-include command line option
@item -no-include
Do not expand include files.  Macro definitions and other
preprocessing directives in the include file are taken into account,
but the expanded include file does not appear in the output.

This option implies -P.

@cindex -no-simple-macros command line option
@cindex @code{__CTPP_NO_SIMPLE_MACROS_OPT__} macro
@item -no-simple-macros
Do not expand simple macros (macros without arguments).  Definitions
for simple macros are also retained in the output.
This option defines the @code{__CTPP_NO_SIMPLE_MACROS_OPT__} built-in macro.

@cindex -std command line option
@item -std=@var{language-standard}
Included for compatibility with GNU cpp.  The following
@var{language-standard} values cause ctpp to follow ANSI and ISO
language guidelines: @samp{iso9899:1990}, @samp{c89},
@samp{iso9899:199409}, @samp{iso9899:1999}, @samp{c99}, @samp{iso9899:199x},
@samp{c9x}, @samp{gnu89}, @samp{gnu99}, and @samp{gnu9x}.

The following @var{language-standard} values cause ctpp to follow C++ 
language standards: @samp{c++98}, and @samp{gnu++98}.

@cindex -target-help command line option
@item -target-help
Print a message displaying ctpp's command line options and exit.

@cindex -trigraphs command line option
@cindex @code{__CTPP_USE_TRIGRAPHS_OPT__} macro
@item -trigraphs
Translate trigraphs into their ASCII equivalents.
This option defines the @code{__CTPP_USE_TRIGRAPHS_OPT__} built-in macro.

@cindex -U command line option
@item -U @var{symbol}
Undefine macro @var{symbol} before processing the main input file.

@cindex -u command line option
@cindex -undef command line option
@item -u
@item -undef
Undefine system and compiler specific built-in macros before
processing.  Does not affect macros defined with the @samp{-imacros} or
@samp{-include} options, or macros defined with the @samp{-D} command
line option.

@cindex -v command line option
@item -v 
Print ctpp's version number and the list of include paths before
preprocessing the input.

@cindex -version command line option
@item -version
Print ctpp's version number before preprocessing the input file.

@cindex --version command line option
@item --version
Print ctpp's version number and exit.

@cindex -w command line option
@cindex @code{__CTPP_NO_WARNINGS_OPT__} macro
@item -w
Suppress all warning messages, including messages generated by other
-W@var{type} options.
This option defines the @code{__CTPP_NO_WARNINGS_OPT__} built-in macro.

@cindex -Wall command line option
@cindex @code{__CTPP_WARNNESTEDCOMMENTS_OPT__} macro
@cindex @code{__CTPP_WARNUNDEFSYMBOLS_OPT__} macro
@cindex @code{__CTPP_WARN_TRIGRAPHS_OPT__} macro
@item -Wall
Issue warning messages about all preprocessor statements that do not
conform with C99, including the deprecated macro keywords
@samp{#ident} and @samp{#sccs}, and the use of extension keywords like
@samp{#assert}, @samp{#unassert}, and @samp{#warning}, and macro
expansions in @samp{#error} and @samp{#warning} messages.

@samp{-Wall} also includes @samp{-Wcomment}, @samp{-Wtrigraphs}, 
@samp{-Wundef}, and @samp{-$}.

This option defines the @code{__CTPP_WARNNESTEDCOMMENTS_OPT__},
@code{__CTPP_WARNUNDEFSYMBOLS_OPT__}, and
@code{__CTPP_WARN_TRIGRAPHS_OPT__} built-in macros.

@cindex -Wcomment command line option
@cindex -Wcomments command line option
@cindex @code{__CTPP_WARNNESTEDCOMMENTS_OPT__} macro
@item -Wcomment
@item -Wcomments
Warn if a comment start character sequence appears within a
comment.
This option defines the @code{__CTPP_WARNNESTEDCOMMENTS_OPT__} built-in macro.

@cindex -Werror command line option.
@item -Werror
Treat warnings as errors.  If a warning is encountered, handle it as
an error and discontinue processing.

@cindex -Wtrigraphs command line option
@item -Wtrigraphs
Print a warning when the preprocessor encounters a trigraph sequence,
if trigraphs are enabled.

@cindex -Wundef command line option
@item -Wundef
Print a warning message if a symbol is undefined.  GNU @command{cpp}
silently evaluates undefined symbols to @var{false}, and this is the
default behavior of ctpp.

@cindex -Wunused-macros command line option
@cindex @code{__CTPP_WARN_UNUSED_OPT__} macro
@item -Wunused-macros
Print a warning message if a symbol is unused when it is undefined, or
after the input file is processed.  This option defines the 
@code{__CTPP_WARN_UNUSED_OPT__} built-in macro.

@cindex -x command line option
@item -x @var{lang}
@var{lang} can be either @samp{c}, @samp{c++}, @samp{objective-c}, or
@samp{assembler-with-cpp}.  These options are equivalent to the 
@samp{-lang-}@var{x} options.  Becuae C is ctpp's default 
language, only @samp{-x} @var{c++} has any effect.

@end table

Ctpp also recognizes the the following options for compatibility with
GNU @command{cpp}, but they are no-ops: 
@samp{-ansi},
@samp{-CC},
@samp{-fno-show-column},
@samp{-lang-c},
@samp{-lang-objc},
@samp{-lang-objc++},
@samp{-lint},
@samp{-nostdinc++},
@samp{-pedantic},
@samp{-pedantic-errors},
@samp{-traditional},
@samp{-traditional-cpp},
@samp{-remap},
@samp{-Wendif-labels},
@samp{-Wimport},
@samp{-Wsystem-headers}, and
@samp{-Wtraditional}.

Ctpp does not implement the following options and will exit:
@samp{-iwithprefixbefore},
@samp{-ftabstop}, and
@samp{-std}.


@node Include, Macros, Options, Top

@heading Including Header Files
@cindex Library header files
@cindex Header files
@cindex Include paths

The most common task of the preprocessor is to include library header
files in the source code file.  These files normally have the
extension @file{.h}.  The preprocessor replaces
@samp{#include} macro directives with the text of a header file, which
contains common definitions of system or program variables and macros.
C99 specifies preprocessor inclusions include both library and program
specific header files.

An @samp{#include} statement with the following form:
@example
#include <stdio.h>
@end example

causes the preprocessor to search the system's library directories
for the header file.  An @samp{#include} statement with the following
form:
@example
#include "mymacros.h"
@end example

@subheading Primary Include Paths

The location of library header files depends on the operating system.
On POSIX systems, the distributed library header files are normally in
@file{/usr/include}, and local library files are in
@file{/usr/local/include}.  Ctpp always includes these directories in
the search path for header files, so the preprocessor searches these 
directories:
@example
  /usr/local/include
  /usr/include
@end example

Ctpp adds directories named with the @samp{-I} option to the end of
the list of directory paths.  @xref{Options}.

Note that the preprocessor always searches @file{/usr/local/include}
first, so that it includes a locally modified header file in 
@file{/usr/local/include} if a file of the same name exists in
@file{/usr/include}. 


@subheading GCC Library Paths

If the system's target compiler is GNU GCC, machine specific include
files are in
@file{@var{libdir}/gcc-lib/@var{TARGET}/@var{VERSION}/include}.  If
the compiler is GCC 2.95.4 and the system is a PC compatible with
GNU/Linux installed, the path for the compiler's include files would
be:
@example
  /usr/lib/gcc-lib/i386-linux/2.95.4/include
@end example
GCC also
can use the path @file{/usr/@var{TARGET}/include}.  For compatibility
with GCC, the search path for library files is as follows
@example
  /usr/local/include
  /usr/lib/gcc-lib/i386-linux/2.95.4/include
  /usr/i386-linux/include
  /usr/include
@end example

Again, ctpp adds directories named with the @samp{-I} option to the
directory search list. @xref{Options}.

@subsubheading Secondary Include Paths

For compatibility with GNU @command{cpp}, ctpp also includes a
secondary include path list, which you can use in complex build
processes.  The secondary include path list is determined by
ctpp's command line options.  @xref{Options}.

@subheading Environment Variable Paths
@cindex Environment variable paths
@cindex Include path environment variables
@cindex CPATH environment variable
@cindex C_INCLUDE_PATH environment variable
@cindex CPLUS_INCLUDE_PATH environment variable
@cindex GCC_LIBDIR environment variable

You can also tell the preprocessor to include library search paths by
setting environment variables.  If defined, the preprocessor adds the
directory paths named in the environment variables @samp{CPATH},
@samp{C_INCLUDE_PATH}, and @samp{CPLUS_INCLUDE_PATH} to its list of
include directory paths.

The values of these variables are one or more paths, separated by
colons (@samp{:}), similar to the format of the @samp{PATH}
environment variable.

With the default language options, which tell ctpp to process ANSI and
ISO C99 input, the preprocessor adds the paths defined by @samp{CPATH}
and @samp{C_INCLUDE_PATH} to the include path list after the
preprocessor's built-in search path list.  With @samp{-lang-c++} as a
command line option, the preprocessor adds the directories defined in
@samp{CPLUS_INCLUDE_PATH}.

Ctpp also checks the environment variable @samp{GCC_LIBDIR} for the
GNU C compiler include directory.  The value should be the path
of the compiler's include subdirectory.  

When looking for the compiler's include directory, ctpp first checks
@samp{GCC_LIBDIR}, then the library directory configured when ctpp was
built, if any, then the directory named by the GCC compiler.

@node Macros, Directives, Include, Top

@heading Macro Definitions
@cindex Macros

Ctpp follows the C99 guidelines for macro replacements.  When you
define a macro, with @samp{-D} and other command line options
@pxref{Options}, or with the @samp{#define} directive in the input
file @pxref{Directives}, the preprocessor replaces the macro name with
its replacement text wherever it appears in the output.
@example
  #define HOST_OS linux-gnu

  #if HOST_OS == linux-gnu
  printf ("Your operating system is GNU/Linux.\n");
  #endif

===>

  #if linux-gnu == linux-gnu
  printf ("Your operating system is GNU/Linux.\n");
  #endif

@end example


If you define only the name of a macro without replacement text, its
definition is, "1."  The preprocessor can then test its value in
conditionals.

@subheading Macro Arguments
@cindex Macro Arguments

You can also provide macros with argument replacements.  When the
preprocessor replaces the macro text, it also replaces the parameters
in the macro definition with the macro arguments in the input text.
Here is an example, with the macro expansion.
@example
   #define MAX(a,b) ((a) > (b) ? (a) : (b))

   printf ("%d is greater.\n", MAX(1,3));

===>

   printf ("%d is greater.\n", ((1) > (3) ? (1) : (3)));

@end example

When writing a macro definition, it is often a good idea to enclose
macros and parameters in parentheses, so that the preprocessor
interprets the macro and its arguments as complete expressions and not
as part of another expression.

@subheading Quoting and Concatenation
@cindex Macro Quoting
@cindex Macro Concatenation

The @samp{#} operator, when used within a macro, quotes the 
text immediately following it.  The @samp{##} operator 
concatenates the text before and after it.

@example
   #define PLAN_NAME(n) _PLAN_NAME(Plan##n)
   #define _PLAN_NAME(n) #n

   printf ("Attached is a copy of %s.\n", PLAN_NAME(B))

===>

   printf ("Attached is a copy of %s.\n", _PLAN_NAME(PlanB))

===>

   printf ("Attached is a copy of %s.\n", "PlanB")

@end example

Note that the C standard requires that preprocessors rescan macro
replacements, so you can replace a macro with another macro, as
in this example.

@subheading Variadic Macros
@cindex Variadic macros

Variadic macros accept argument lists with a variable number of
arguments.  If an ellipsis (@samp{...}) occurs in the parameter
definition of a macro, then the preprocessor replaces the placeholder
(@samp{__VA_ARGS__}) in the body of the macro with the list of
arguments given when the macro is expanded.
@example

   #define stdprintf(...) printf (stdout, __VA_ARGS__)

   #define MAJOR_VERSION 3
   #define MINOR_VERSION 4

   stdprintf ("%d.%d", MAJOR_VERSION, MINOR_VERSION);

===>

   printf (stdout, "%d.%d", 3, 4);

@end example

Ctpp attempts to avoid making assumptions about white space and
precedence when expanding macro arguments, beyond what is specified by
C language standards.  For example, if a concatenation operator
(@samp{##}) occurs within a parameter list, ctpp deletes the white
space between the arguments and the operator.  However, when pasting
and quoting tokens, ctpp follows a left-to-right order of
evaluation, and the preprocessor rescans the arguments after replacing
them.  You need to take care that the results are what you intended.
@example

   stdprintf ("%f", MAJOR_VERSION##.##MINOR_VERSION);

===>

   printf (stderr, "%f", 3##.##3);

===>

   printf (stderr, "%f", 3.3);

@end example

Note that the following will @emph{not} work:
@example

   stdprintf ("%s", #MAJOR_VERSION##.##MINOR_VERSION);

===>

   stdprintf (stdout, "%s", "3".3);

@end example

@subheading Predefined Macros
@cindex Predefined macros

The C standard specifies that preprocessors define internal macros
that provide information about the input text.  Preprocessors also
commonly define macros that provide information about the compiler and
operating system.

Ctpp provides the following built-in macros.

@table @code
@cindex __FILE__ macro
@item __FILE__
Expands to a string with the name of the input file.

@cindex __LINE__ macro
@item __LINE__
Expands to a decimal digit with the number of the line in the input
file that ctpp is processing.

@cindex __DATE__ macro
@item __DATE__
Expands to a string with the current date.

@cindex __TIME__ macro
@item __TIME__
Expands to a string with the current time.

@end table

Ctpp also provides the ability to define compiler, machine, and
operating specific macros.  For examples, look in 
@file{ctpp/config}, and read the comments in @file{ctpp/builtins.c}.

@node Directives, Copying, Macros, Top

@heading Preprocessing Directives
@cindex Preprocessing directives

Preprocessors use directives to include library files, define macros,
display information, and conditionally process or exclude segments of
the input text.  The directives start with a pound sign @samp{#} in
the first column of a line, and the directives and their arguments
continue to the end of the line.

Ctpp provides the directives defined by the C99 standard, as well as
extensions to that standard.

@table @code
@cindex #assert preprocessor directive
@item #assert @var{pred}[(@var{value})]

The @samp{#assert} directive defines an assertion.  Each assertion
predicate has an optional defined value, which can be either a token
or an expression.  You can test assertions in the input by preceding
the predicate with a pound (@samp{#}) sign.

@example
  #assert system (unix)

  #if #system (unix)
  .
  .
  .
  #endif
@end example

If the assertion fails, the preprocessor calls abort () and
terminates.

In addition to tokens, you can also use expressions as assertion
values.  Here is a simple example.

@example
  #assert gcc_version (2)

  #if #gcc_version (__GNUC__)
  .
  .
  .
  #endif
@end example

If you test an assertion predicate without a value, the preprocessor 
evaluates the predicate to true for @emph{any} value of the assertion.

@samp{#assert} is an extension to C99.  If you use the @samp{-Wall} 
option, ctpp prints a warning if the directive appears in the input
text.

@cindex #define preprocessing directive
@item #define @var{symbol} [@var{value}]

Defines a macro that replaces @var{symbol} with @var{value} wherever
@var{symbol} appears in the input text.  Macro replacement is
discussed in a previous section.  @xref{Macros}.

@cindex #elif preprocessing directive
@item #elif @var{expr}

When used as an additional conditional branch after an @samp{#if}
directive, includes input text until the next @samp{#elif},
@samp{#else}, or @samp{#endif} if previous @samp{#if} and @samp{#elif} 
expressions evaluate to False and @var{expr} evaluates to True.

@cindex #else preprocessing directive
@item #else

When used as an additional conditional branch after an @samp{#if} or
@samp{#elif} directive, includes the input text until the next
@samp{#endif} if the previous conditional expressions evaluate to
False.

@cindex #endif preprocessing directive
@item #endif

Ends a section of conditional text from the preceding @samp{#if},
@samp{#ifdef}, @samp{#ifndef}, @samp{#elif}, or @samp{#else} directive.

@cindex #error preprocessing directive
@item #error @var{message}

Prints an error message on the terminal and terminates preprocessing.

Note that @samp{#error} expands macro tokens in its argument.  This is
an extension to standard C and generates a warning message if
@samp{-Wall} is present as a command line option.

@cindex #ident preprocessing directive
@item #ident

The @samp{#ident} directive is deprecated and should not be used in
new code.  If @samp{-Wall} is present as a command line option, ctpp 
generates a warning message if the directive appears in the input text.

@cindex #if preprocessing directive
@cindex defined operator
@item #if @var{expr}

If @var{expr} evaluates to True, include the input text in the output 
until the next @samp{#elif}, @samp{#else}, or @samp{#endif} directive.

You can also use @samp{#if} to test whether a symbol is defined, in a
manner similar to @samp{#ifdef}, by using the @samp{define} function
in an expression.  The following statements function identically.
@example
   #if defined (__GNUC__)

   #ifdef __GNUC__
@end example

@cindex #ifdef preprocessing directive
@item #ifdef @var{expr}

If @var{expr} is defined include the input text until the next 
@samp{#else} or @samp{#elif} directive.

@cindex #ifndef preprocessing directive
@item #ifndef @var{expr}

Operates similarly to @samp{#ifdef}, but the conditional evaluates
to True of @var{expr} evaluates to False.

@cindex #line preprocessor directive
@item #line @var{args}

The @samp{#line} directive adjusts the line number and, optionally, the
name of the input file.  The directive can have the following forms.

@table @code
@item #line @var{n}
The directive numbers all lines beginning with the following line
beginning with @var{n}, which is a decimal integer.

@item #line @var{n} @var{file}
Numbers the following lines beginning with @var{n}, and sets the
name of the input file to @var{file}, which is a quoted string.

@item #line @var{args}
The preprocessor expands @var{args} before adjusting the line number
and input file name.  @var{args} must expand to one of the 
previous forms.
@end table

@cindex #include preprocessor directive
@item #include @var{include_filename}|@var{args}

Replaces the directive with the text of the file named in the
argument.  The argument has several forms depending on which
directories need to be searched for the file, and command line options
direct ctpp to search additional include file
directories. @xref{Include}.

If @var{args} is an expression, it must expand to the name of an
include file as described above.

@cindex #include_next preprocessor directive
@item #include_next @var{include_filename}|@var{args}

The @samp{#include_next} directive replaces the text of the directive
with the file named in its argument.  If ctpp included a header file
with the same name earlier, @samp{#include_next} searches the
include directories after the directory with contains the first
include file.

If @var{args} is an expression, it must expand to the name of an
include file.  @xref{Include}.

@samp{#include_next} is an extension to C99.  If you use the @samp{-Wall} 
option, ctpp prints a warning if the directive appears in the input
text.

@cindex #pragma preprocessor directive
@cindex _Pragma operator
@item #pragma

The @samp{#pragma} directive recognizes the GNU GCC pragmas that
apply to preprocessing.

@table @code
@cindex #pragma GCC dependency
@item #pragma GCC dependency @var{args}

Causes the preprocessor to issue a warning if a file given as
an argument has been updated more recently than the input text.

@cindex #pragma GCC poison
@item #pragma GCC poison @var{args}

Causes the preprocessor to stop processing and exit if it encounters 
any of the identifiers in the input text that are given as arguments
to the pragma.

@end table

The @samp{_Pragma} operator takes as its argument a literal string 
which is identical to the arguments that would be given to a 
@samp{#pragma} directive.

@cindex #undef preprocessing directive
@item #undef @var{macro_symbol}

Undefines a macro defined by an earlier @samp{#define} directive.

@cindex #warning preprocessor directive
@item #warning @var{message}

The @samp{#warning} preprocessor directive prints a message to 
standard output and continues processing the input.

@samp{#warning} is an extension to C99.  If you use the @samp{-Wall}
option, ctpp prints a warning if the directive appears in the input
text.  If @samp{-Wall} is given on the command line, and the argument 
contains macros to be expanded, ctpp also issues a warning in this 
case.

@cindex #import preprocessor directive
@item #import
@cindex #sccs preprocessor directive
@item #sccs
@cindex #unassert preprocessor directive
@item #unassert

The @samp{#import}, @samp{#sccs}, and @samp{#unassert} preprocessor
directives are deprecated and should not be used in new code.

@end table



@node Copying, Index, Directives, Top

@heading GNU Free Documentation License
@cindex GNU Free Documentation License
@example
		GNU Free Documentation License
		  Version 1.2, November 2002


 Copyright (C) 2000,2001,2002  Free Software Foundation, Inc.
     51 Franklin St, Fifth Floor, Boston, MA  02110-1301  USA
 Everyone is permitted to copy and distribute verbatim copies
 of this license document, but changing it is not allowed.


0. PREAMBLE

The purpose of this License is to make a manual, textbook, or other
functional and useful document "free" in the sense of freedom: to
assure everyone the effective freedom to copy and redistribute it,
with or without modifying it, either commercially or noncommercially.
Secondarily, this License preserves for the author and publisher a way
to get credit for their work, while not being considered responsible
for modifications made by others.

This License is a kind of "copyleft", which means that derivative
works of the document must themselves be free in the same sense.  It
complements the GNU General Public License, which is a copyleft
license designed for free software.

We have designed this License in order to use it for manuals for free
software, because free software needs free documentation: a free
program should come with manuals providing the same freedoms that the
software does.  But this License is not limited to software manuals;
it can be used for any textual work, regardless of subject matter or
whether it is published as a printed book.  We recommend this License
principally for works whose purpose is instruction or reference.


1. APPLICABILITY AND DEFINITIONS

This License applies to any manual or other work, in any medium, that
contains a notice placed by the copyright holder saying it can be
distributed under the terms of this License.  Such a notice grants a
world-wide, royalty-free license, unlimited in duration, to use that
work under the conditions stated herein.  The "Document", below,
refers to any such manual or work.  Any member of the public is a
licensee, and is addressed as "you".  You accept the license if you
copy, modify or distribute the work in a way requiring permission
under copyright law.

A "Modified Version" of the Document means any work containing the
Document or a portion of it, either copied verbatim, or with
modifications and/or translated into another language.

A "Secondary Section" is a named appendix or a front-matter section of
the Document that deals exclusively with the relationship of the
publishers or authors of the Document to the Document's overall subject
(or to related matters) and contains nothing that could fall directly
within that overall subject.  (Thus, if the Document is in part a
textbook of mathematics, a Secondary Section may not explain any
mathematics.)  The relationship could be a matter of historical
connection with the subject or with related matters, or of legal,
commercial, philosophical, ethical or political position regarding
them.

The "Invariant Sections" are certain Secondary Sections whose titles
are designated, as being those of Invariant Sections, in the notice
that says that the Document is released under this License.  If a
section does not fit the above definition of Secondary then it is not
allowed to be designated as Invariant.  The Document may contain zero
Invariant Sections.  If the Document does not identify any Invariant
Sections then there are none.

The "Cover Texts" are certain short passages of text that are listed,
as Front-Cover Texts or Back-Cover Texts, in the notice that says that
the Document is released under this License.  A Front-Cover Text may
be at most 5 words, and a Back-Cover Text may be at most 25 words.

A "Transparent" copy of the Document means a machine-readable copy,
represented in a format whose specification is available to the
general public, that is suitable for revising the document
straightforwardly with generic text editors or (for images composed of
pixels) generic paint programs or (for drawings) some widely available
drawing editor, and that is suitable for input to text formatters or
for automatic translation to a variety of formats suitable for input
to text formatters.  A copy made in an otherwise Transparent file
format whose markup, or absence of markup, has been arranged to thwart
or discourage subsequent modification by readers is not Transparent.
An image format is not Transparent if used for any substantial amount
of text.  A copy that is not "Transparent" is called "Opaque".

Examples of suitable formats for Transparent copies include plain
ASCII without markup, Texinfo input format, LaTeX input format, SGML
or XML using a publicly available DTD, and standard-conforming simple
HTML, PostScript or PDF designed for human modification.  Examples of
transparent image formats include PNG, XCF and JPG.  Opaque formats
include proprietary formats that can be read and edited only by
proprietary word processors, SGML or XML for which the DTD and/or
processing tools are not generally available, and the
machine-generated HTML, PostScript or PDF produced by some word
processors for output purposes only.

The "Title Page" means, for a printed book, the title page itself,
plus such following pages as are needed to hold, legibly, the material
this License requires to appear in the title page.  For works in
formats which do not have any title page as such, "Title Page" means
the text near the most prominent appearance of the work's title,
preceding the beginning of the body of the text.

A section "Entitled XYZ" means a named subunit of the Document whose
title either is precisely XYZ or contains XYZ in parentheses following
text that translates XYZ in another language.  (Here XYZ stands for a
specific section name mentioned below, such as "Acknowledgements",
"Dedications", "Endorsements", or "History".)  To "Preserve the Title"
of such a section when you modify the Document means that it remains a
section "Entitled XYZ" according to this definition.

The Document may include Warranty Disclaimers next to the notice which
states that this License applies to the Document.  These Warranty
Disclaimers are considered to be included by reference in this
License, but only as regards disclaiming warranties: any other
implication that these Warranty Disclaimers may have is void and has
no effect on the meaning of this License.


2. VERBATIM COPYING

You may copy and distribute the Document in any medium, either
commercially or noncommercially, provided that this License, the
copyright notices, and the license notice saying this License applies
to the Document are reproduced in all copies, and that you add no other
conditions whatsoever to those of this License.  You may not use
technical measures to obstruct or control the reading or further
copying of the copies you make or distribute.  However, you may accept
compensation in exchange for copies.  If you distribute a large enough
number of copies you must also follow the conditions in section 3.

You may also lend copies, under the same conditions stated above, and
you may publicly display copies.


3. COPYING IN QUANTITY

If you publish printed copies (or copies in media that commonly have
printed covers) of the Document, numbering more than 100, and the
Document's license notice requires Cover Texts, you must enclose the
copies in covers that carry, clearly and legibly, all these Cover
Texts: Front-Cover Texts on the front cover, and Back-Cover Texts on
the back cover.  Both covers must also clearly and legibly identify
you as the publisher of these copies.  The front cover must present
the full title with all words of the title equally prominent and
visible.  You may add other material on the covers in addition.
Copying with changes limited to the covers, as long as they preserve
the title of the Document and satisfy these conditions, can be treated
as verbatim copying in other respects.

If the required texts for either cover are too voluminous to fit
legibly, you should put the first ones listed (as many as fit
reasonably) on the actual cover, and continue the rest onto adjacent
pages.

If you publish or distribute Opaque copies of the Document numbering
more than 100, you must either include a machine-readable Transparent
copy along with each Opaque copy, or state in or with each Opaque copy
a computer-network location from which the general network-using
public has access to download using public-standard network protocols
a complete Transparent copy of the Document, free of added material.
If you use the latter option, you must take reasonably prudent steps,
when you begin distribution of Opaque copies in quantity, to ensure
that this Transparent copy will remain thus accessible at the stated
location until at least one year after the last time you distribute an
Opaque copy (directly or through your agents or retailers) of that
edition to the public.

It is requested, but not required, that you contact the authors of the
Document well before redistributing any large number of copies, to give
them a chance to provide you with an updated version of the Document.


4. MODIFICATIONS

You may copy and distribute a Modified Version of the Document under
the conditions of sections 2 and 3 above, provided that you release
the Modified Version under precisely this License, with the Modified
Version filling the role of the Document, thus licensing distribution
and modification of the Modified Version to whoever possesses a copy
of it.  In addition, you must do these things in the Modified Version:

A. Use in the Title Page (and on the covers, if any) a title distinct
   from that of the Document, and from those of previous versions
   (which should, if there were any, be listed in the History section
   of the Document).  You may use the same title as a previous version
   if the original publisher of that version gives permission.
B. List on the Title Page, as authors, one or more persons or entities
   responsible for authorship of the modifications in the Modified
   Version, together with at least five of the principal authors of the
   Document (all of its principal authors, if it has fewer than five),
   unless they release you from this requirement.
C. State on the Title page the name of the publisher of the
   Modified Version, as the publisher.
D. Preserve all the copyright notices of the Document.
E. Add an appropriate copyright notice for your modifications
   adjacent to the other copyright notices.
F. Include, immediately after the copyright notices, a license notice
   giving the public permission to use the Modified Version under the
   terms of this License, in the form shown in the Addendum below.
G. Preserve in that license notice the full lists of Invariant Sections
   and required Cover Texts given in the Document's license notice.
H. Include an unaltered copy of this License.
I. Preserve the section Entitled "History", Preserve its Title, and add
   to it an item stating at least the title, year, new authors, and
   publisher of the Modified Version as given on the Title Page.  If
   there is no section Entitled "History" in the Document, create one
   stating the title, year, authors, and publisher of the Document as
   given on its Title Page, then add an item describing the Modified
   Version as stated in the previous sentence.
J. Preserve the network location, if any, given in the Document for
   public access to a Transparent copy of the Document, and likewise
   the network locations given in the Document for previous versions
   it was based on.  These may be placed in the "History" section.
   You may omit a network location for a work that was published at
   least four years before the Document itself, or if the original
   publisher of the version it refers to gives permission.
K. For any section Entitled "Acknowledgements" or "Dedications",
   Preserve the Title of the section, and preserve in the section all
   the substance and tone of each of the contributor acknowledgements
   and/or dedications given therein.
L. Preserve all the Invariant Sections of the Document,
   unaltered in their text and in their titles.  Section numbers
   or the equivalent are not considered part of the section titles.
M. Delete any section Entitled "Endorsements".  Such a section
   may not be included in the Modified Version.
N. Do not retitle any existing section to be Entitled "Endorsements"
   or to conflict in title with any Invariant Section.
O. Preserve any Warranty Disclaimers.

If the Modified Version includes new front-matter sections or
appendices that qualify as Secondary Sections and contain no material
copied from the Document, you may at your option designate some or all
of these sections as invariant.  To do this, add their titles to the
list of Invariant Sections in the Modified Version's license notice.
These titles must be distinct from any other section titles.

You may add a section Entitled "Endorsements", provided it contains
nothing but endorsements of your Modified Version by various
parties--for example, statements of peer review or that the text has
been approved by an organization as the authoritative definition of a
standard.

You may add a passage of up to five words as a Front-Cover Text, and a
passage of up to 25 words as a Back-Cover Text, to the end of the list
of Cover Texts in the Modified Version.  Only one passage of
Front-Cover Text and one of Back-Cover Text may be added by (or
through arrangements made by) any one entity.  If the Document already
includes a cover text for the same cover, previously added by you or
by arrangement made by the same entity you are acting on behalf of,
you may not add another; but you may replace the old one, on explicit
permission from the previous publisher that added the old one.

The author(s) and publisher(s) of the Document do not by this License
give permission to use their names for publicity for or to assert or
imply endorsement of any Modified Version.


5. COMBINING DOCUMENTS

You may combine the Document with other documents released under this
License, under the terms defined in section 4 above for modified
versions, provided that you include in the combination all of the
Invariant Sections of all of the original documents, unmodified, and
list them all as Invariant Sections of your combined work in its
license notice, and that you preserve all their Warranty Disclaimers.

The combined work need only contain one copy of this License, and
multiple identical Invariant Sections may be replaced with a single
copy.  If there are multiple Invariant Sections with the same name but
different contents, make the title of each such section unique by
adding at the end of it, in parentheses, the name of the original
author or publisher of that section if known, or else a unique number.
Make the same adjustment to the section titles in the list of
Invariant Sections in the license notice of the combined work.

In the combination, you must combine any sections Entitled "History"
in the various original documents, forming one section Entitled
"History"; likewise combine any sections Entitled "Acknowledgements",
and any sections Entitled "Dedications".  You must delete all sections
Entitled "Endorsements".


6. COLLECTIONS OF DOCUMENTS

You may make a collection consisting of the Document and other documents
released under this License, and replace the individual copies of this
License in the various documents with a single copy that is included in
the collection, provided that you follow the rules of this License for
verbatim copying of each of the documents in all other respects.

You may extract a single document from such a collection, and distribute
it individually under this License, provided you insert a copy of this
License into the extracted document, and follow this License in all
other respects regarding verbatim copying of that document.


7. AGGREGATION WITH INDEPENDENT WORKS

A compilation of the Document or its derivatives with other separate
and independent documents or works, in or on a volume of a storage or
distribution medium, is called an "aggregate" if the copyright
resulting from the compilation is not used to limit the legal rights
of the compilation's users beyond what the individual works permit.
When the Document is included in an aggregate, this License does not
apply to the other works in the aggregate which are not themselves
derivative works of the Document.

If the Cover Text requirement of section 3 is applicable to these
copies of the Document, then if the Document is less than one half of
the entire aggregate, the Document's Cover Texts may be placed on
covers that bracket the Document within the aggregate, or the
electronic equivalent of covers if the Document is in electronic form.
Otherwise they must appear on printed covers that bracket the whole
aggregate.


8. TRANSLATION

Translation is considered a kind of modification, so you may
distribute translations of the Document under the terms of section 4.
Replacing Invariant Sections with translations requires special
permission from their copyright holders, but you may include
translations of some or all Invariant Sections in addition to the
original versions of these Invariant Sections.  You may include a
translation of this License, and all the license notices in the
Document, and any Warranty Disclaimers, provided that you also include
the original English version of this License and the original versions
of those notices and disclaimers.  In case of a disagreement between
the translation and the original version of this License or a notice
or disclaimer, the original version will prevail.

If a section in the Document is Entitled "Acknowledgements",
"Dedications", or "History", the requirement (section 4) to Preserve
its Title (section 1) will typically require changing the actual
title.


9. TERMINATION

You may not copy, modify, sublicense, or distribute the Document except
as expressly provided for under this License.  Any other attempt to
copy, modify, sublicense or distribute the Document is void, and will
automatically terminate your rights under this License.  However,
parties who have received copies, or rights, from you under this
License will not have their licenses terminated so long as such
parties remain in full compliance.


10. FUTURE REVISIONS OF THIS LICENSE

The Free Software Foundation may publish new, revised versions
of the GNU Free Documentation License from time to time.  Such new
versions will be similar in spirit to the present version, but may
differ in detail to address new problems or concerns.  See
http://www.gnu.org/copyleft/.

Each version of the License is given a distinguishing version number.
If the Document specifies that a particular numbered version of this
License "or any later version" applies to it, you have the option of
following the terms and conditions either of that specified version or
of any later version that has been published (not as a draft) by the
Free Software Foundation.  If the Document does not specify a version
number of this License, you may choose any version ever published (not
as a draft) by the Free Software Foundation.


ADDENDUM: How to use this License for your documents

To use this License in a document you have written, include a copy of
the License in the document and put the following copyright and
license notices just after the title page:

    Copyright (c)  YEAR  YOUR NAME.
    Permission is granted to copy, distribute and/or modify this document
    under the terms of the GNU Free Documentation License, Version 1.2
    or any later version published by the Free Software Foundation;
    with no Invariant Sections, no Front-Cover Texts, and no Back-Cover Texts.
    A copy of the license is included in the section entitled "GNU
    Free Documentation License".

If you have Invariant Sections, Front-Cover Texts and Back-Cover Texts,
replace the "with...Texts." line with this:

    with the Invariant Sections being LIST THEIR TITLES, with the
    Front-Cover Texts being LIST, and with the Back-Cover Texts being LIST.

If you have Invariant Sections without Cover Texts, or some other
combination of the three, merge those two alternatives to suit the
situation.

If your document contains nontrivial examples of program code, we
recommend releasing these examples in parallel under your choice of
free software license, such as the GNU General Public License,
to permit their use in free software.

@end example

@node Index, , Copying, Top

@unnumbered Index

@syncodeindex fn cp

@printindex cp

