SYMTAB

	SYMBOL TABLE EXTRACTOR:

	 This program will extract global symbols from 	either an
	.OBJ, .STB, or .EXE (you MUST specify the /EXECUTABLE qualifier)
	file and generate an output definition file of the symbols. 
	Symbols may be selected by using standard VMS wildcarding using 
	the /FACILITY qualifier. The output file type is specified by 
	the /LANGUAGE qualifier.

	 This program was originally written for use with SDA, but
	there are now other "languages" supported. Use /LANGUAGE=NULL
	/OUTPUT=TT: to examine .STB and .EXE files on the terminal.

	The languages currently supported are:

	DCL	    - Global symbols can be used by DCL procedures

	LINKER	    - Used to create UNIVERSAL=xxx for input to the linker

	NULL	    - Outputs the symbol name and value

	SDA	    - Used to define image symbols for use within SDA
		      This is enormously use when debugging software using SDA.
		      If all routine names follow a standard convention, you
		      extract all of the routine symbols, which can be used
		      to define all of the routines for SDA. Then you can
		      reference routines by name rather than by computing the
		      address each time. Also, SHOW STACK will identify any
		      routines on the stack by name, rather than by driver plus
		      some offset.

	SDL	    - Used to define image symbols for use by SDL to create
		      definitions for any SDL supported language

	 To run this program, you may either place it in the system directory
	(SYS$SYSTEM) and make the .CLD definition part of your system DCLTABLES
	(SET COMMAND/TABLE=SYS$LIBRARY:DCLTABLES.EXE/OUTPUT=SYS$LIBRARY:DCLTABLE.EXE
	SYMTAB.CLD), or create a symbol pointing to the executable (SYMTAB :==
	$some_dir:SYMTAB.EXE) and still specify the qualifiers as if it were a
	native command. For example: 

	SYMTAB/FACILITY=(SS$*,EXE$GL*)/LANGUAGE=NULL/OUTPUT=TT:

	will display all symbols starting with SS$, or EXE$GL*. When extracting
	symbols from images, specify the /EXECUTABLE qualifier, for example:

	SYMTAB/FAC=*BRK/LAN=NUL/OUT=TT: SYS$LOADABLE_IMAGES:SYSTEM_DEBUG.EXE/EXECUTABLE

	will display all symbols than end in BRK; in this case one.

	QUALIFIERS:

	/ALL	    Outputs all types of symbols found; used for debugging

	/EXECUTABLE Specifies that the input file is an image.

	/FACILITY   VMS wildcard name of the symbols to extract; for a list,
		    enclose the list in parentheses

	/LOG	    Doesn't do much at this time

	/LANGUAGE   Specifies for which language to output the symbol definition
		    Keywords are:

		    DCL		Creates DCL symbol definitions

		    LINKER	Use for specifying UNIVERSAL=symbol-name

		    NULL	Outputs symbol and type

		    SDA		Creates SDA commands for defining symbol;
				specify the /OFFSET qualifier when creating
				routine definitions

		    SDL		Creates SDL CONSTANT definitions; replace
				this if you have a specific language you
				want symbols for

	/OFFSET	    Used only for SDL output; specify the reference point all
		    symbols are to be offset from, i.e. driver name. For
		    example: SYMTAB/LANG=SDL/OFF=XXDRIVER/FAC=XX_* and all 
		    symbol definitions will be of the form :
		    DEFINE XX_symbol = XX_symbol + XXDRIVER

	/OUTPUT	    Specifies the output file to write. If this qualifier is
		    not specified, the output file will be the name of the
		    input file with a .SYM file type

	 In order to process executable images, an UNDOCUMENTED RMS
	function is used. This is because an image file is somewhat
	of a hybrid; it contains fixed length blocks (image stuff - ISDs,
	etc.), followed by variable length records containing the global
	symbol table, the debug symbol table, and the debug module table.
	Therefore, the image file is opened as a fixed block file in
	order to read the header which points to the variable length
	records at the end of the file. RMS's pointers are then updated
	to point to the variable length portion, and no one is the wiser.

	The default input filetype is .STB; the output file will
	have type .SYM and with the same name as the input.


	 This was hacked together in about a day and a half, apologies for 
	the lack of complete commenting.

			Brian Catlin
			Closed Loop Control
			7-DEC-1990