/* 

 *   Copyright (c) 1999, 2002 Michael J. Roberts.  All Rights Reserved.

 *   

 *   Please see the accompanying license file, LICENSE.TXT, for information

 *   on using and copying this software.  

 */

/*

Name

  tctarg.h - TADS 3 Compiler Target Selector

Function

Notes

Modified

  04/30/99 MJRoberts  - Creation

*/

#ifndef TCTARG_H

#define TCTARG_H

/* ------------------------------------------------------------------------ */

/*

 *   Target Selection.

 *   

 *   SEE ALSO: tctargty.h - target type header selector

 *   

 *   As the parser scans the source stream, it constructs a parse tree

 *   that represent the parsed form of the source.  After the parsing

 *   pass, the parse tree contains all of the information necessary to

 *   generate code for the translation.

 *   

 *   The parse tree objects are actually the code generators.  So, as the

 *   scanner parses the source file, it must create parse tree objects for

 *   the appropriate target architecture.  However, we want to keep the

 *   scanner independent of the target architecture -- we want the same

 *   scanner to be usable for any target architecture for which we can

 *   provide a code generator.

 *   

 *   To accomplish this, we define a base class for parse tree nodes; the

 *   scanner is only interested in this base class interface.  Then, for

 *   each target architecture, we create a subclass of each parse tree

 *   node that contains the code generator for that node type for the

 *   target.

 *   

 *   However, the scanner must still know enough to create the appropriate

 *   subclass of each parse tree node.  This file contains the target

 *   selection switch that mediates the independence of the scanner from

 *   the target code generator, but still allows the scanner to create the

 *   correct type of parse tree nodes for the desired target.  For each

 *   parse tree node type that the scanner must create, we #define a

 *   generic symbol to a target-specific subclass.  The scanner uses the

 *   generic symbol, but we expand the macro when compiling the compiler

 *   to the correct target.

 *   

 *   Because the target selection is made through macros, the target

 *   architecture is fixed at compile time.  However, the same scanner

 *   source code can be compiled into multiple target compilers.  

 */

/*

 *   Before including this file, #define the appropriate target type.

 *   This should usually be done in the makefile, since this is a

 *   compile-time selection.

 *   

 *   To add a new code generator, define the appropriate subclasses in a

 *   new file.  Add a new #ifdef-#include sequence below that includes the

 *   subclass definitions for your code generator.

 *   

 *   Note that each target uses the same names for the final subclasses.

 *   We choose the target at link time when building the compiler

 *   executable, so we must compile and link only a single target

 *   architecture into a given build of the compiler.  

 */

/* 

 *   make sure TC_TARGET_DEFINED__ isn't defined, so we can use it to

 *   sense whether we defined a code generator or not

 */

#undef TCTARG_TARGET_DEFINED__

/* ------------------------------------------------------------------------ */

/*

 *   T3 Virtual Machine Code Generator 

 */

#ifdef TC_TARGET_T3

#include "tct3.h"

#define TCTARG_TARGET_DEFINED__

#endif

/* ------------------------------------------------------------------------ */

/*

 *   JavaScript code generator

 */

#ifdef TC_TARGET_JS

#include "tcjs.h"

#define TCTARG_TARGET_DEFINED__

#endif

/* ------------------------------------------------------------------------ */

/*

 *   ensure that a code generator was defined - if not, the compilation

 *   cannot proceed 

 */

#ifndef TCTARG_TARGET_DEFINED__

#error No code generator target is defined.  A code generator must be defined in your makefile.  See tctarg.h for details.

#endif

#endif /* TCTARG_H */