treelang.texi

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\input texinfo  @c -*-texinfo-*-

@c NOTE THIS IS NOT A GOOD EXAMPLE OF HOW TO DO A MANUAL. FIXME!!!
@c NOTE THIS IS NOT A GOOD EXAMPLE OF HOW TO DO A MANUAL. FIXME!!!


@c %**start of header
@setfilename treelang.info

@include gcc-common.texi

@set copyrights-treelang 1995,1996,1997,1998,1999,2000,2001,2002,2003,2004,2005

@set email-general gcc@@gcc.gnu.org
@set email-bugs gcc-bugs@@gcc.gnu.org or bug-gcc@@gnu.org
@set email-patches gcc-patches@@gcc.gnu.org 
@set path-treelang gcc/gcc/treelang

@ifset VERSION_PACKAGE
@set which-treelang @value{version-GCC} @value{VERSION_PACKAGE}
@end ifset
@ifclear VERSION_PACKAGE
@set which-treelang @value{version-GCC}
@end ifclear
@set which-GCC GCC

@set email-josling tej@@melbpc.org.au
@set www-josling http://www.geocities.com/timjosling

@c This tells @include'd files that they're part of the overall TREELANG doc
@c set.  (They might be part of a higher-level doc set too.)
@set DOC-TREELANG

@c @setfilename usetreelang.info
@c @setfilename maintaintreelang.info
@c To produce the full manual, use the "treelang.info" setfilename, and
@c make sure the following do NOT begin with '@c' (and the @clear lines DO)
@set INTERNALS
@set USING
@c To produce a user-only manual, use the "usetreelang.info" setfilename, and
@c make sure the following does NOT begin with '@c':
@c @clear INTERNALS
@c To produce a maintainer-only manual, use the "maintaintreelang.info" setfilename,
@c and make sure the following does NOT begin with '@c':
@c @clear USING

@ifset INTERNALS
@ifset USING
@settitle Using and Maintaining GNU Treelang
@end ifset
@end ifset
@c seems reasonable to assume at least one of INTERNALS or USING is set...
@ifclear INTERNALS
@settitle Using GNU Treelang
@end ifclear
@ifclear USING
@settitle Maintaining GNU Treelang
@end ifclear
@c then again, have some fun
@ifclear INTERNALS
@ifclear USING
@settitle Doing Very Little at all with GNU Treelang
@end ifclear
@end ifclear

@syncodeindex fn cp
@syncodeindex vr cp
@c %**end of header

@c Cause even numbered pages to be printed on the left hand side of
@c the page and odd numbered pages to be printed on the right hand
@c side of the page.  Using this, you can print on both sides of a
@c sheet of paper and have the text on the same part of the sheet.

@c The text on right hand pages is pushed towards the right hand
@c margin and the text on left hand pages is pushed toward the left
@c hand margin.
@c (To provide the reverse effect, set bindingoffset to -0.75in.)

@c @tex
@c \global\bindingoffset=0.75in
@c \global\normaloffset =0.75in
@c @end tex

@copying
Copyright @copyright{} @value{copyrights-treelang} Free Software Foundation, Inc.

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 the
Invariant Sections being ``GNU General Public License'', the Front-Cover
texts being (a) (see below), and with the Back-Cover Texts being (b)
(see below).  A copy of the license is included in the section entitled
``GNU Free Documentation License''.

(a) The FSF's Front-Cover Text is:

     A GNU Manual

(b) The FSF's Back-Cover Text is:

     You have freedom to copy and modify this GNU Manual, like GNU
     software.  Copies published by the Free Software Foundation raise
     funds for GNU development.
@end copying

@ifnottex
@dircategory Software development
@direntry
* treelang: (treelang).                  The GNU Treelang compiler.
@end direntry
@ifset INTERNALS
@ifset USING
This file documents the use and the internals of the GNU Treelang
(@code{treelang}) compiler.  At the moment this manual is not
incorporated into the main GCC manual as it is incomplete.  It
corresponds to the @value{which-treelang} version of @code{treelang}.
@end ifset
@end ifset
@ifclear USING
This file documents the internals of the GNU Treelang (@code{treelang}) compiler.
It corresponds to the @value{which-treelang} version of @code{treelang}.
@end ifclear
@ifclear INTERNALS
This file documents the use of the GNU Treelang (@code{treelang}) compiler.
It corresponds to the @value{which-treelang} version of @code{treelang}.
@end ifclear

Published by the Free Software Foundation
51 Franklin Street, Fifth Floor
Boston, MA 02110-1301 USA

@insertcopying
@end ifnottex

@setchapternewpage odd
@c @finalout
@titlepage
@ifset INTERNALS
@ifset USING
@title Using and Maintaining GNU Treelang
@end ifset
@end ifset
@ifclear INTERNALS
@title Using GNU Treelang
@end ifclear
@ifclear USING
@title Maintaining GNU Treelang
@end ifclear
@versionsubtitle
@author Tim Josling
@page
@vskip 0pt plus 1filll
Published by the Free Software Foundation @*
51 Franklin Street, Fifth Floor@*
Boston, MA 02110-1301, USA@*
@c Last printed ??ber, 19??.@*
@c Printed copies are available for $? each.@*
@c ISBN ???
@sp 1
@insertcopying
@end titlepage
@page

@ifnottex

@node Top, Copying,, (dir)
@top Introduction
@cindex Introduction

@ifset INTERNALS
@ifset USING
This manual documents how to run, install and maintain @code{treelang}.
It also documents the features and incompatibilities in the @value{which-treelang}
version of @code{treelang}.
@end ifset
@end ifset

@ifclear INTERNALS
This manual documents how to run and install @code{treelang}.
It also documents the features and incompatibilities in the @value{which-treelang}
version of @code{treelang}.
@end ifclear
@ifclear USING
This manual documents how to maintain @code{treelang}.
It also documents the features and incompatibilities in the @value{which-treelang}
version of @code{treelang}.
@end ifclear

@end ifnottex

@menu
* Copying::                     
* Contributors::                
* GNU Free Documentation License::                
* Funding::                     
* Getting Started::             
* What is GNU Treelang?::       
* Lexical Syntax::              
* Parsing Syntax::              
* Compiler Overview::           
* TREELANG and GCC::            
* Compiler::                    
* Other Languages::             
* treelang internals::          
* Open Questions::              
* Bugs::                        
* Service::                     
* Projects::                    
* Index::                       

@detailmenu
 --- The Detailed Node Listing ---

Other Languages

* Interoperating with C and C++::  

treelang internals

* treelang files::              
* treelang compiler interfaces::  
* Hints and tips::              

treelang compiler interfaces

* treelang driver::             
* treelang main compiler::      

treelang main compiler

* Interfacing to toplev.c::     
* Interfacing to the garbage collection::  
* Interfacing to the code generation code. ::  

Reporting Bugs

* Sending Patches::             

@end detailmenu
@end menu

@include gpl.texi

@include fdl.texi

@node Contributors

@unnumbered Contributors to GNU Treelang
@cindex contributors
@cindex credits

Treelang was based on 'toy' by Richard Kenner, and also uses code from
the GCC core code tree.  Tim Josling first created the language and
documentation, based on the GCC Fortran compiler's documentation
framework.  Treelang was updated to use the TreeSSA infrastructure by
James A. Morrison.

@itemize @bullet
@item
The packaging and compiler portions of GNU Treelang are based largely
on the GCC compiler.
@xref{Contributors,,Contributors to GCC,GCC,Using and Maintaining GCC},
for more information.

@item
There is no specific run-time library for treelang, other than the
standard C runtime.

@item
It would have been difficult to build treelang without access to Joachim
Nadler's guide to writing a front end to GCC (written in German).  A
translation of this document into English is available via the
CobolForGCC project or via the documentation links from the GCC home
page @uref{http://gcc.gnu.org}.
@end itemize

@include funding.texi

@node Getting Started
@chapter Getting Started
@cindex getting started
@cindex new users
@cindex newbies
@cindex beginners

Treelang is a sample language, useful only to help people understand how
to implement a new language front end to GCC.  It is not a useful
language in itself other than as an example or basis for building a new
language.  Therefore only language developers are likely to have an
interest in it.

This manual assumes familiarity with GCC, which you can obtain by using
it and by reading the manuals @samp{Using the GNU Compiler Collection (GCC)}
and @samp{GNU Compiler Collection (GCC) Internals}.

To install treelang, follow the GCC installation instructions, 
taking care to ensure you specify treelang in the configure step by adding
treelang to the list of languages specified by @option{--enable-languages}, 
e.g.@: @samp{--enable-languages=all,treelang}.

If you're generally curious about the future of
@code{treelang}, see @ref{Projects}.
If you're curious about its past,
see @ref{Contributors}.

To see a few of the questions maintainers of @code{treelang} have,
and that you might be able to answer,
see @ref{Open Questions}.

@ifset USING
@node What is GNU Treelang?, Lexical Syntax, Getting Started, Top
@chapter What is GNU Treelang?
@cindex concepts, basic
@cindex basic concepts

GNU Treelang, or @code{treelang}, is designed initially as a free
replacement for, or alternative to, the 'toy' language, but which is
amenable to inclusion within the GCC source tree. 

@code{treelang} is largely a cut down version of C, designed to showcase
the features of the GCC code generation back end.  Only those features
that are directly supported by the GCC code generation back end are
implemented.  Features are implemented in a manner which is easiest and
clearest to implement.  Not all or even most code generation back end
features are implemented.  The intention is to add features incrementally
until most features of the GCC back end are implemented in treelang.

The main features missing are structures, arrays and pointers.

A sample program follows:

@smallexample
// @r{function prototypes}
// @r{function 'add' taking two ints and returning an int}
external_definition int add(int arg1, int arg2);
external_definition int subtract(int arg3, int arg4);
external_definition int first_nonzero(int arg5, int arg6);
external_definition int double_plus_one(int arg7);

// @r{function definition}
add 
@{
  // @r{return the sum of arg1 and arg2}
  return arg1 + arg2;
@}

        
subtract 
@{
  return arg3 - arg4;
@}

double_plus_one
@{
  // @r{aaa is a variable, of type integer and allocated at the start of}
  // @r{the function}
  automatic int aaa;
  // @r{set aaa to the value returned from add, when passed arg7 and arg7 as}
  // @r{the two parameters}
  aaa=add(arg7, arg7);
  aaa=add(aaa, aaa);
  aaa=subtract(subtract(aaa, arg7), arg7) + 1;
  return aaa;
@}

first_nonzero
@{
  // @r{C-like if statement}
  if (arg5)
    @{
      return arg5;
    @}
  else
    @{
    @}
  return arg6;
@}
@end smallexample

@node Lexical Syntax, Parsing Syntax, What is GNU Treelang?, Top
@chapter Lexical Syntax
@cindex Lexical Syntax

Treelang programs consist of whitespace, comments, keywords and names.
@itemize @bullet

@item
Whitespace consists of the space character, a tab, and the end of line
character.  Line terminations are as defined by the
standard C library.  Whitespace is ignored except within comments,
and where it separates parts of the program.  In the example below, A and
B are two separate names separated by whitespace. 

@smallexample
A B
@end smallexample

@item
Comments consist of @samp{//} followed by any characters up to the end
of the line.  C style comments (/* */) are not supported.  For example,
the assignment below is followed by a not very helpful comment.

@smallexample
x = 1; // @r{Set X to 1}
@end smallexample

@item
Keywords consist of any of the following reserved words or symbols:

@itemize @bullet
@item @{
used to start the statements in a function
@item @}
used to end the statements in a function
@item (
start list of function arguments, or to change the precedence of operators in
an expression
@item )
end list or prioritized operators in expression
@item ,
used to separate parameters in a function prototype or in a function call 
@item ;
used to end a statement
@item +
addition, or unary plus for signed literals
@item - 
subtraction, or unary minus for signed literals
@item = 
assignment
@item ==
equality test
@item if
begin IF statement
@item else
begin 'else' portion of IF statement
@item static