This is gasp.info, produced by makeinfo version 4.0 from
/usr/src/gnu/usr.bin/binutils/gas/doc/gasp.texi.

START-INFO-DIR-ENTRY
* gasp: (gasp).                     The GNU Assembler Preprocessor
END-INFO-DIR-ENTRY

   Copyright (C) 1994, 1995 Free Software Foundation, Inc.

   Permission is granted to make and distribute verbatim copies of this
manual provided the copyright notice and this permission notice are
preserved on all copies.

   Permission is granted to copy and distribute modified versions of
this manual under the conditions for verbatim copying, provided also
that the entire resulting derived work is distributed under the terms
of a permission notice identical to this one.

   Permission is granted to copy and distribute translations of this
manual into another language, under the above conditions for modified
versions.


File: gasp.info,  Node: Top,  Next: Overview,  Up: (dir)

GASP
****

   GASP is a preprocessor for assembly programs.

   This file describes version 1 of GASP.

   Steve Chamberlain wrote GASP; Roland Pesch wrote this manual.

* Menu:

* Overview::                    What is GASP?
* Invoking GASP::               Command line options.
* Commands::                    Preprocessor commands.
* Index::                       Index.


File: gasp.info,  Node: Overview,  Next: Invoking GASP,  Prev: Top,  Up: Top

What is GASP?
*************

   The primary purpose of the GNU assembler is to assemble the output of
other programs--notably compilers.  When you have to hand-code
specialized routines in assembly, that means the GNU assembler is an
unfriendly processor: it has no directives for macros, conditionals, or
many other conveniences that you might expect.

   In some cases you can simply use the C preprocessor, or a generalized
preprocessor like M4; but this can be awkward, since none of these
things are designed with assembly in mind.

   GASP fills this need.  It is expressly designed to provide the
facilities you need with hand-coded assembly code.  Implementing it as a
preprocessor, rather than part of the assembler, allows the maximum
flexibility: you can use it with hand-coded assembly, without paying a
penalty of added complexity in the assembler you use for compiler
output.

   Here is a small example to give the flavor of GASP.  This input to
GASP

             .MACRO  saveregs from=8 to=14
     count   .ASSIGNA \from
             ! save r\from..r\to
             .AWHILE  \&count LE \to
             mov     r\&count,@-sp
     count   .ASSIGNA  \&count + 1
             .AENDW
             .ENDM
     
             saveregs from=12
     
     bar:    mov     #H'dead+10,r0
     foo     .SDATAC "hello"<10>
             .END

generates this assembly program:

             ! save r12..r14
             mov     r12,@-sp
             mov     r13,@-sp
             mov     r14,@-sp
     
     bar:    mov     #57005+10,r0
     foo:    .byte   6,104,101,108,108,111,10


File: gasp.info,  Node: Invoking GASP,  Next: Commands,  Prev: Overview,  Up: Top

Command Line Options
********************

   The simplest way to use GASP is to run it as a filter and assemble
its output.  In Unix and its ilk, you can do this, for example:

     $ gasp prog.asm | as -o prog.o

   Naturally, there are also a few command-line options to allow you to
request variations on this basic theme.  Here is the full set of
possibilities for the GASP command line.

     gasp  [ -a | --alternate ]
           [ -c CHAR | --commentchar CHAR ]
           [ -d | --debug ]  [ -h | --help ] [ -M | --mri ]
           [ -o OUTFILE | --output OUTFILE ]
           [ -p | --print ]  [ -s | --copysource ]
           [ -u | --unreasonable ]  [ -v | --version ]
           INFILE ...

`INFILE ...'
     The input file names.  You must specify at least one input file;
     if you specify more, GASP preprocesses them all, concatenating the
     output in the order you list the INFILE arguments.

     Mark the end of each input file with the preprocessor command
     `.END'.  *Note Miscellaneous commands: Other Commands.

`-a'
`--alternate'
     Use alternative macro syntax.  *Note Alternate macro syntax:
     Alternate, for a discussion of how this syntax differs from the
     default GASP syntax.

`-c 'CHAR''
`--commentchar 'CHAR''
     Use CHAR as the comment character.  The default comment character
     is `!'.  For example, to use a semicolon as the comment character,
     specify `-c ';'' on the GASP command line.  Since assembler
     command characters often have special significance to command
     shells, it is a good idea to quote or escape CHAR when you specify
     a comment character.

     For the sake of simplicity, all examples in this manual use the
     default comment character `!'.

`-d'
`--debug'
     Show debugging statistics.  In this version of GASP, this option
     produces statistics about the string buffers that GASP allocates
     internally.  For each defined buffersize S, GASP shows the number
     of strings N that it allocated, with a line like this:

          strings size S : N

     GASP displays these statistics on the standard error stream, when
     done preprocessing.

`-h'
`--help'
     Display a summary of the GASP command line options.

`-M'
`--mri'
     Use MRI compatibility mode.  Using this option causes GASP to
     accept the syntax and pseudo-ops used by the Microtec Research
     `ASM68K' assembler.

`-o OUTFILE'
`--output OUTFILE'
     Write the output in a file called OUTFILE.  If you do not use the
     `-o' option, GASP writes its output on the standard output stream.

`-p'
`--print'
     Print line numbers.  GASP obeys this option _only_ if you also
     specify `-s' to copy source lines to its output.  With `-s -p',
     GASP displays the line number of each source line copied
     (immediately after the comment character at the beginning of the
     line).

`-s'
`--copysource'
     Copy the source lines to the output file.  Use this option to see
     the effect of each preprocessor line on the GASP output.  GASP
     places a comment character (`!' by default) at the beginning of
     each source line it copies, so that you can use this option and
     still assemble the result.

`-u'
`--unreasonable'
     Bypass "unreasonable expansion" limit.  Since you can define GASP
     macros inside other macro definitions, the preprocessor normally
     includes a sanity check.  If your program requires more than 1,000
     nested expansions, GASP normally exits with an error message.  Use
     this option to turn off this check, allowing unlimited nested
     expansions.

`-v'
`--version'
     Display the GASP version number.


File: gasp.info,  Node: Commands,  Next: Index,  Prev: Invoking GASP,  Up: Top

Preprocessor Commands
*********************

   GASP commands have a straightforward syntax that fits in well with
assembly conventions.  In general, a command extends for a line, and may
have up to three fields: an optional label, the command itself, and
optional arguments to the command.  You can write commands in upper or
lower case, though this manual shows them in upper case.  *Note Details
of the GASP syntax: Syntax Details, for more information.

* Menu:

* Conditionals::
* Loops::
* Variables::
* Macros::
* Data::
* Listings::
* Other Commands::
* Syntax Details::
* Alternate::


File: gasp.info,  Node: Conditionals,  Next: Loops,  Up: Commands

Conditional assembly
====================

   The conditional-assembly directives allow you to include or exclude
portions of an assembly depending on how a pair of expressions, or a
pair of strings, compare.

   The overall structure of conditionals is familiar from many other
contexts.  `.AIF' marks the start of a conditional, and precedes
assembly for the case when the condition is true.   An optional
`.AELSE' precedes assembly for the converse case, and an `.AENDI' marks
the end of the condition.

   You may nest conditionals up to a depth of 100; GASP rejects nesting
beyond that, because it may indicate a bug in your macro structure.

   Conditionals are primarily useful inside macro definitions, where you
often need different effects depending on argument values.  *Note
Defining your own directives: Macros, for details about defining macros.

`.AIF EXPRA CMP EXPRB'
`.AIF "STRA" CMP "STRB"'
     The governing condition goes on the same line as the `.AIF'
     preprocessor command.  You may compare either two strings, or two
     expressions.

     When you compare strings, only two conditional CMP comparison
     operators are available: `EQ' (true if STRA and STRB are
     identical), and `NE' (the opposite).

     When you compare two expressions, _both expressions must be
     absolute_ (*note Arithmetic expressions in GASP: Expressions.).
     You can use these CMP comparison operators with expressions:

    `EQ'
          Are EXPRA and EXPRB equal?  (For strings, are STRA and STRB
          identical?)

    `NE'
          Are EXPRA and EXPRB different?  (For strings, are STRA and
          STRB different?

    `LT'
          Is EXPRA less than EXPRB?  (Not allowed for strings.)

    `LE'
          Is EXPRA less than or equal to EXPRB?  (Not allowed for
          strings.)

    `GT'
          Is EXPRA greater than EXPRB?  (Not allowed for strings.)

    `GE'
          Is EXPRA greater than or equal to EXPRB?  (Not allowed for
          strings.)

`.AELSE'
     Marks the start of assembly code to be included if the condition
     fails.  Optional, and only allowed within a conditional (between
     `.AIF' and `.AENDI').

`.AENDI'
     Marks the end of a conditional assembly.


File: gasp.info,  Node: Loops,  Next: Variables,  Prev: Conditionals,  Up: Commands

Repetitive sections of assembly
===============================

   Two preprocessor directives allow you to repeatedly issue copies of
the same block of assembly code.

`.AREPEAT AEXP'
`.AENDR'
     If you simply need to repeat the same block of assembly over and
     over a fixed number of times, sandwich one instance of the
     repeated block between `.AREPEAT' and `.AENDR'.  Specify the
     number of copies as AEXP (which must be an absolute expression).
     For example, this repeats two assembly statements three times in
     succession:

                  .AREPEAT        3
                  rotcl   r2
                  div1    r0,r1
                  .AENDR

`.AWHILE EXPRA CMP EXPRB'
`.AENDW'
`.AWHILE STRA CMP STRB'
`.AENDW'
     To repeat a block of assembly depending on a conditional test,
     rather than repeating it for a specific number of times, use
     `.AWHILE'.  `.AENDW' marks the end of the repeated block.  The
     conditional comparison works exactly the same way as for `.AIF',
     with the same comparison operators (*note Conditional assembly:
     Conditionals.).

     Since the terms of the comparison must be absolute expression,
     `.AWHILE' is primarily useful within macros.  *Note Defining your
     own directives: Macros.

   You can use the `.EXITM' preprocessor directive to break out of
loops early (as well as to break out of macros).  *Note Defining your
own directives: Macros.


File: gasp.info,  Node: Variables,  Next: Macros,  Prev: Loops,  Up: Commands

Preprocessor variables
======================

   You can use variables in GASP to represent strings, registers, or
the results of expressions.

   You must distinguish two kinds of variables:
  1. Variables defined with `.EQU' or `.ASSIGN'.  To evaluate this kind
     of variable in your assembly output, simply mention its name.  For
     example, these two lines define and use a variable `eg':

          eg     .EQU   FLIP-64
                 ...
                 mov.l  eg,r0

     _Do not use_ this kind of variable in conditional expressions or
     while loops; GASP only evaluates these variables when writing
     assembly output.

  2. Variables for use during preprocessing.  You can define these with
     `.ASSIGNC' or `.ASSIGNA'.  To evaluate this kind of variable,
     write `\&' before the variable name; for example,

          opcit  .ASSIGNA  47
                 ...
                 .AWHILE  \&opcit GT 0
                 ...
                 .AENDW

     GASP treats macro arguments almost the same way, but to evaluate
     them you use the prefix `\' rather than `\&'.  *Note Defining your
     own directives: Macros.

`PVAR .EQU EXPR'
     Assign preprocessor variable PVAR the value of the expression
     EXPR.  There are no restrictions on redefinition; use `.EQU' with
     the same PVAR as often as you find it convenient.

`PVAR .ASSIGN EXPR'
     Almost the same as `.EQU', save that you may not redefine PVAR
     using `.ASSIGN' once it has a value.

`PVAR .ASSIGNA AEXPR'
     Define a variable with a numeric value, for use during
     preprocessing.  AEXPR must be an absolute expression.  You can
     redefine variables with `.ASSIGNA' at any time.

`PVAR .ASSIGNC "STR"'
     Define a variable with a string value, for use during
     preprocessing.  You can redefine variables with `.ASSIGNC' at any
     time.

`PVAR .REG (REGISTER)'
     Use `.REG' to define a variable that represents a register.  In
     particular, REGISTER is _not evaluated_ as an expression.  You may
     use `.REG' at will to redefine register variables.

   All these directives accept the variable name in the "label"
position, that is at the left margin.  You may specify a colon after
the variable name if you wish; the first example above could have
started `eg:' with the same effect.


File: gasp.info,  Node: Macros,  Next: Data,  Prev: Variables,  Up: Commands

Defining your own directives
============================

   The commands `.MACRO' and `.ENDM' allow you to define macros that
generate assembly output.  You can use these macros with a syntax
similar to built-in GASP or assembler directives.  For example, this
definition specifies a macro `SUM' that adds together a range of
consecutive registers:

             .MACRO  SUM FROM=0, TO=9
             ! \FROM \TO
             mov     r\FROM,r10
     COUNT   .ASSIGNA        \FROM+1
             .AWHILE \&COUNT LE \TO
             add     r\&COUNT,r10
     COUNT   .ASSIGNA        \&COUNT+1
             .AENDW
             .ENDM

With that definition, `SUM 0,5' generates this assembly output:

             ! 0 5
             mov     r0,r10
             add     r1,r10
             add     r2,r10
             add     r3,r10
             add     r4,r10
             add     r5,r10

`.MACRO MACNAME'
`.MACRO MACNAME MACARGS ...'
     Begin the definition of a macro called MACNAME.  If your macro
     definition requires arguments, specify their names after the macro
     name, separated by commas or spaces.  You can supply a default
     value for any macro argument by following the name with `=DEFLT'.
     For example, these are all valid `.MACRO' statements:

    `.MACRO COMM'
          Begin the definition of a macro called `COMM', which takes no
          arguments.

    `.MACRO PLUS1 P, P1'
    `.MACRO PLUS1 P P1'
          Either statement begins the definition of a macro called
          `PLUS1', which takes two arguments; within the macro
          definition, write `\P' or `\P1' to evaluate the arguments.

    `.MACRO RESERVE_STR P1=0 P2'
          Begin the definition of a macro called `RESERVE_STR', with two
          arguments.  The first argument has a default value, but not
          the second.  After the definition is complete, you can call
          the macro either as `RESERVE_STR A,B' (with `\P1' evaluating
          to A and `\P2' evaluating to B), or as `RESERVE_STR ,B' (with
          `\P1' evaluating as the default, in this case `0', and `\P2'
          evaluating to B).

     When you call a macro, you can specify the argument values either
     by position, or by keyword.  For example, `SUM 9,17' is equivalent
     to `SUM TO=17, FROM=9'.  Macro arguments are preprocessor variables
     similar to the variables you define with `.ASSIGNA' or `.ASSIGNC';
     in particular, you can use them in conditionals or for loop
     control.  (The only difference is the prefix you write to evaluate
     the variable: for a macro argument, write `\ARGNAME', but for a
     preprocessor variable, write `\&VARNAME'.)

`NAME .MACRO'
`NAME .MACRO ( MACARGS ... )'
     An alternative form of introducing a macro definition: specify the
     macro name in the label position, and the arguments (if any)
     between parentheses after the name.  Defaulting rules and usage
     work the same way as for the other macro definition syntax.

`.ENDM'
     Mark the end of a macro definition.

`.EXITM'
     Exit early from the current macro definition, `.AREPEAT' loop, or
     `.AWHILE' loop.

`\@'
     GASP maintains a counter of how many macros it has executed in
     this pseudo-variable; you can copy that number to your output with
     `\@', but _only within a macro definition_.

`LOCAL NAME [ , ... ]'
     _Warning: `LOCAL' is only available if you select "alternate macro
     syntax" with `-a' or `--alternate'._  *Note Alternate macro
     syntax: Alternate.

     Generate a string replacement for each of the NAME arguments, and
     replace any instances of NAME in each macro expansion.  The
     replacement string is unique in the assembly, and different for
     each separate macro expansion.  `LOCAL' allows you to write macros
     that define symbols, without fear of conflict between separate
     macro expansions.


File: gasp.info,  Node: Data,  Next: Listings,  Prev: Macros,  Up: Commands

Data output
===========

   In assembly code, you often need to specify working areas of memory;
depending on the application, you may want to initialize such memory or
not.  GASP provides preprocessor directives to help you avoid
repetitive coding for both purposes.

   You can use labels as usual to mark the data areas.

* Menu:

* Initialized::
* Uninitialized::


File: gasp.info,  Node: Initialized,  Next: Uninitialized,  Up: Data

Initialized data
----------------

   These are the GASP directives for initialized data, and the standard
GNU assembler directives they expand to:

`.DATA EXPR, EXPR, ...'
`.DATA.B EXPR, EXPR, ...'
`.DATA.W EXPR, EXPR, ...'
`.DATA.L EXPR, EXPR, ...'
     Evaluate arithmetic expressions EXPR, and emit the corresponding
     `as' directive (labelled with LAB).  The unqualified `.DATA' emits
     `.long'; `.DATA.B' emits `.byte'; `.DATA.W' emits `.short'; and
     `.DATA.L' emits `.long'.

     For example, `foo .DATA 1,2,3' emits `foo: .long 1,2,3'.

`.DATAB REPEAT, EXPR'
`.DATAB.B REPEAT, EXPR'
`.DATAB.W REPEAT, EXPR'
`.DATAB.L REPEAT, EXPR'
     Make `as' emit REPEAT copies of the value of the expression EXPR
     (using the `as' directive `.fill').  `.DATAB.B' repeats one-byte
     values; `.DATAB.W' repeats two-byte values; and `.DATAB.L' repeats
     four-byte values.  `.DATAB' without a suffix repeats four-byte
     values, just like `.DATAB.L'.

     REPEAT must be an absolute expression with a positive value.

`.SDATA "STR" ...'
     String data.  Emits a concatenation of bytes, precisely as you
     specify them (in particular, _nothing is added to mark the end_ of
     the string).  *Note String and numeric constants: Constants, for
     details about how to write strings.  `.SDATA' concatenates multiple
     arguments, making it easy to switch between string
     representations.  You can use commas to separate the individual
     arguments for clarity, if you choose.

`.SDATAB REPEAT, "STR" ...'
     Repeated string data.  The first argument specifies how many
     copies of the string to emit; the remaining arguments specify the
     string, in the same way as the arguments to `.SDATA'.

`.SDATAZ "STR" ...'
     Zero-terminated string data.  Just like `.SDATA', except that
     `.SDATAZ' writes a zero byte at the end of the string.

`.SDATAC "STR" ...'
     Count-prefixed string data.  Just like `.SDATA', except that GASP
     precedes the string with a leading one-byte count.  For example,
     `.SDATAC "HI"' generates `.byte 2,72,73'.  Since the count field
     is only one byte, you can only use `.SDATAC' for strings less than
     256 bytes in length.


File: gasp.info,  Node: Uninitialized,  Prev: Initialized,  Up: Data

Uninitialized data
------------------

   Use the `.RES', `.SRES', `.SRESC', and `.SRESZ' directives to
reserve memory and leave it uninitialized.  GASP resolves these
directives to appropriate calls of the GNU `as' `.space' directive.

`.RES COUNT'
`.RES.B COUNT'
`.RES.W COUNT'
`.RES.L COUNT'
     Reserve room for COUNT uninitialized elements of data.  The suffix
     specifies the size of each element: `.RES.B' reserves COUNT bytes,
     `.RES.W' reserves COUNT pairs of bytes, and `.RES.L' reserves
     COUNT quartets.  `.RES' without a suffix is equivalent to `.RES.L'.

`.SRES COUNT'
`.SRES.B COUNT'
`.SRES.W COUNT'
`.SRES.L COUNT'
     `.SRES' is a synonym for `.RES'.

`.SRESC COUNT'
`.SRESC.B COUNT'
`.SRESC.W COUNT'
`.SRESC.L COUNT'
     Like `.SRES', but reserves space for `COUNT+1' elements.

`.SRESZ COUNT'
`.SRESZ.B COUNT'
`.SRESZ.W COUNT'
`.SRESZ.L COUNT'
     Like `.SRES', but reserves space for `COUNT+1' elements.


File: gasp.info,  Node: Listings,  Next: Other Commands,  Prev: Data,  Up: Commands

Assembly listing control
========================

   The GASP listing-control directives correspond to related GNU `as'
directives.

`.PRINT LIST'
`.PRINT NOLIST'
     Print control.  This directive emits the GNU `as' directive
     `.list' or `.nolist', according to its argument.  *Note `.list':
     (as.info)List, for details on how these directives interact.

`.FORM LIN=LN'
`.FORM COL=COLS'
`.FORM LIN=LN COL=COLS'
     Specify the page size for assembly listings: LN represents the
     number of lines, and COLS the number of columns.  You may specify
     either page dimension independently, or both together.  If you do
     not specify the number of lines, GASP assumes 60 lines; if you do
     not specify the number of columns, GASP assumes 132 columns.  (Any
     values you may have specified in previous instances of `.FORM' do
     _not_ carry over as defaults.)  Emits the `.psize' assembler
     directive.

`.HEADING STRING'
     Specify STRING as the title of your assembly listings.  Emits
     `.title "STRING"'.

`.PAGE'
     Force a new page in assembly listings.  Emits `.eject'.


File: gasp.info,  Node: Other Commands,  Next: Syntax Details,  Prev: Listings,  Up: Commands

Miscellaneous commands
======================

`.ALTERNATE'
     Use the alternate macro syntax henceforth in the assembly.  *Note
     Alternate macro syntax: Alternate.

`.ORG'
     This command is recognized, but not yet implemented.  GASP
     generates an error message for programs that use `.ORG'.

`.RADIX S'
     GASP understands numbers in any of base two, eight, ten, or
     sixteen.  You can encode the base explicitly in any numeric
     constant (*note String and numeric constants: Constants.).  If you
     write numbers without an explicit indication of the base, the most
     recent `.RADIX S' command determines how they are interpreted.  S
     is a single letter, one of the following:

    `.RADIX B'
          Base 2.

    `.RADIX Q'
          Base 8.

    `.RADIX D'
          Base 10.  This is the original default radix.

    `.RADIX H'
          Base 16.

     You may specify the argument S in lower case (any of `bqdh') with
     the same effects.

`.EXPORT NAME'
`.GLOBAL NAME'
     Declare NAME global (emits `.global NAME').  The two directives
     are synonymous.

`.PROGRAM'
     No effect: GASP accepts this directive, and silently ignores it.

`.END'
     Mark end of each preprocessor file.  GASP issues a warning if it
     reaches end of file without seeing this command.

`.INCLUDE "STR"'
     Preprocess the file named by STR, as if its contents appeared
     where the `.INCLUDE' directive does.  GASP imposes a maximum limit
     of 30 stacked include files, as a sanity check.

`.ALIGN SIZE'
     Evaluate the absolute expression SIZE, and emit the assembly
     instruction `.align SIZE' using the result.


File: gasp.info,  Node: Syntax Details,  Next: Alternate,  Prev: Other Commands,  Up: Commands

Details of the GASP syntax
==========================

   Since GASP is meant to work with assembly code, its statement syntax
has no surprises for the assembly programmer.

   _Whitespace_ (blanks or tabs; _not_ newline) is partially
significant, in that it delimits up to three fields in a line.  The
amount of whitespace does not matter; you may line up fields in separate
lines if you wish, but GASP does not require that.

   The _first field_, an optional "label", must be flush left in a line
(with no leading whitespace) if it appears at all.  You may use a colon
after the label if you wish; GASP neither requires the colon nor
objects to it (but will not include it as part of the label name).

   The _second field_, which must appear after some whitespace,
contains a GASP or assembly "directive".

   Any _further fields_ on a line are "arguments" to the directive; you
can separate them from one another using either commas or whitespace.

* Menu:

* Markers::
* Constants::
* Symbols::
* Expressions::
* String Builtins::


File: gasp.info,  Node: Markers,  Next: Constants,  Up: Syntax Details

Special syntactic markers
-------------------------

   GASP recognizes a few special markers: to delimit comments, to
continue a statement on the next line, to separate symbols from other
characters, and to copy text to the output literally.  (One other
special marker, `\@', works only within macro definitions; *note
Defining your own directives: Macros..)

   The trailing part of any GASP source line may be a "comment".  A
comment begins with the first unquoted comment character (`!' by
default), or an escaped or doubled comment character (`\!' or `!!' by
default), and extends to the end of a line.  You can specify what
comment character to use with the `-c' option (*note Command Line
Options: Invoking GASP.).  The two kinds of comment markers lead to
slightly different treatment:

`!'
     A single, un-escaped comment character generates an assembly
     comment in the GASP output.  GASP evaluates any preprocessor
     variables (macro arguments, or variables defined with `.ASSIGNA' or
     `.ASSIGNC') present.  For example, a macro that begins like this

                  .MACRO  SUM FROM=0, TO=9
                  ! \FROM \TO

     issues as the first line of output a comment that records the
     values you used to call the macro.

`\!'
`!!'
     Either an escaped comment character, or a double comment character,
     marks a GASP source comment.  GASP does not copy such comments to
     the assembly output.

   To _continue a statement_ on the next line of the file, begin the
second line with the character `+'.

   Occasionally you may want to prevent GASP from preprocessing some
particular bit of text.  To _copy literally_ from the GASP source to
its output, place `\(' before the string to copy, and `)' at the end.
For example, write `\(\!)' if you need the characters `\!' in your
assembly output.

   To _separate a preprocessor variable_ from text to appear
immediately after its value, write a single quote (`'').  For example,
`.SDATA "\P'1"' writes a string built by concatenating the value of `P'
and the digit `1'.  (You cannot achieve this by writing just `\P1',
since `P1' is itself a valid name for a preprocessor variable.)


File: gasp.info,  Node: Constants,  Next: Symbols,  Prev: Markers,  Up: Syntax Details

String and numeric constants
----------------------------

   There are two ways of writing "string constants" in GASP: as literal
text, and by numeric byte value.  Specify a string literal between
double quotes (`"STR"').  Specify an individual numeric byte value as
an absolute expression between angle brackets (`<EXPR>'.  Directives
that output strings allow you to specify any number of either kind of
value, in whatever order is convenient, and concatenate the result.
(Alternate syntax mode introduces a number of alternative string
notations; *note Alternate macro syntax: Alternate..)

   You can write "numeric constants" either in a specific base, or in
whatever base is currently selected (either 10, or selected by the most
recent `.RADIX').

   To write a number in a _specific base_, use the pattern `S'DDD': a
base specifier character S, followed by a single quote followed by
digits DDD.  The base specifier character matches those you can specify
with `.RADIX': `B' for base 2, `Q' for base 8, `D' for base 10, and `H'
for base 16.  (You can write this character in lower case if you
prefer.)


File: gasp.info,  Node: Symbols,  Next: Expressions,  Prev: Constants,  Up: Syntax Details

Symbols
-------

   GASP recognizes symbol names that start with any alphabetic
character, `_', or `$', and continue with any of the same characters or
with digits.  Label names follow the same rules.


File: gasp.info,  Node: Expressions,  Next: String Builtins,  Prev: Symbols,  Up: Syntax Details

Arithmetic expressions in GASP
------------------------------

   There are two kinds of expressions, depending on their result:
"absolute" expressions, which resolve to a constant (that is, they do
not involve any values unknown to GASP), and "relocatable" expressions,
which must reduce to the form

     ADDSYM+CONST-SUBSYM

where ADDSYM and SUBSYM are assembly symbols of unknown value, and
CONST is a constant.

   Arithmetic for GASP expressions follows very similar rules to C.
You can use parentheses to change precedence; otherwise, arithmetic
primitives have decreasing precedence in the order of the following
list.

  1. Single-argument `+' (identity), `-' (arithmetic opposite), or `~'
     (bitwise negation).  _The argument must be an absolute expression._

  2. `*' (multiplication) and `/' (division).  _Both arguments must be
     absolute expressions._

  3. `+' (addition) and `-' (subtraction).  _At least one argument must
     be absolute._

  4. `&' (bitwise and).  _Both arguments must be absolute._

  5. `|' (bitwise or) and `~' (bitwise exclusive or; `^' in C).  _Both
     arguments must be absolute._


File: gasp.info,  Node: String Builtins,  Prev: Expressions,  Up: Syntax Details

String primitives
-----------------

   You can use these primitives to manipulate strings (in the argument
field of GASP statements):

`.LEN("STR")'
     Calculate the length of string `"STR"', as an absolute expression.
     For example, `.RES.B .LEN("sample")' reserves six bytes of memory.

`.INSTR("STRING", "SEG", IX)'
     Search for the first occurrence of SEG after position IX of
     STRING.  For example, `.INSTR("ABCDEFG", "CDE", 0)' evaluates to
     the absolute result `2'.

     The result is `-1' if SEG does not occur in STRING after position
     IX.

`.SUBSTR("STRING",START,LEN)'
     The substring of STRING beginning at byte number START and
     extending for LEN bytes.


File: gasp.info,  Node: Alternate,  Prev: Syntax Details,  Up: Commands

Alternate macro syntax
======================

   If you specify `-a' or `--alternate' on the GASP command line, the
preprocessor uses somewhat different syntax.  This syntax is
reminiscent of the syntax of Phar Lap macro assembler, but it is _not_
meant to be a full emulation of Phar Lap or similar assemblers.  In
particular, GASP does not support directives such as `DB' and `IRP',
even in alternate syntax mode.

   In particular, `-a' (or `--alternate') elicits these differences:

_Preprocessor directives_
     You can use GASP preprocessor directives without a leading `.'
     dot.  For example, you can write `SDATA' with the same effect as
     `.SDATA'.

_LOCAL_
     One additional directive, `LOCAL', is available.  *Note Defining
     your own directives: Macros, for an explanation of how to use
     `LOCAL'.

_String delimiters_
     You can write strings delimited in these other ways besides
     `"STRING"':

    `'STRING''
          You can delimit strings with single-quote charaters.

    `<STRING>'
          You can delimit strings with matching angle brackets.

_single-character string escape_
     To include any single character literally in a string (even if the
     character would otherwise have some special meaning), you can
     prefix the character with `!' (an exclamation mark).  For example,
     you can write `<4.3 !> 5.4!!>' to get the literal text `4.3 >
     5.4!'.

_Expression results as strings_
     You can write `%EXPR' to evaluate the expression EXPR and use the
     result as a string.


File: gasp.info,  Node: Index,  Prev: Commands,  Up: Top

Index
*****

* Menu:

* ! default comment char:                Invoking GASP.
* +:                                     Markers.
* --alternate:                           Invoking GASP.
* --commentchar 'CHAR':                  Invoking GASP.
* --copysource:                          Invoking GASP.
* --debug:                               Invoking GASP.
* --help:                                Invoking GASP.
* --mri:                                 Invoking GASP.
* --output OUTFILE:                      Invoking GASP.
* --print:                               Invoking GASP.
* --unreasonable:                        Invoking GASP.
* --version:                             Invoking GASP.
* -a:                                    Invoking GASP.
* -c 'CHAR':                             Invoking GASP.
* -d:                                    Invoking GASP.
* -h:                                    Invoking GASP.
* -M:                                    Invoking GASP.
* -o OUTFILE:                            Invoking GASP.
* -p:                                    Invoking GASP.
* -s:                                    Invoking GASP.
* -u:                                    Invoking GASP.
* -v:                                    Invoking GASP.
* .AELSE:                                Conditionals.
* .AENDI:                                Conditionals.
* .AENDR:                                Loops.
* .AENDW:                                Loops.
* .AIF "STRA" CMP "STRB":                Conditionals.
* .AIF EXPRA CMP EXPRB:                  Conditionals.
* .ALIGN SIZE:                           Other Commands.
* .ALTERNATE:                            Other Commands.
* .AREPEAT AEXP:                         Loops.
* .AWHILE EXPRA CMP EXPRB:               Loops.
* .AWHILE STRA CMP STRB:                 Loops.
* .DATA EXPR, EXPR, ...:                 Initialized.
* .DATA.B EXPR, EXPR, ...:               Initialized.
* .DATA.L EXPR, EXPR, ...:               Initialized.
* .DATA.W EXPR, EXPR, ...:               Initialized.
* .DATAB REPEAT, EXPR:                   Initialized.
* .DATAB.B REPEAT, EXPR:                 Initialized.
* .DATAB.L REPEAT, EXPR:                 Initialized.
* .DATAB.W REPEAT, EXPR:                 Initialized.
* .END:                                  Other Commands.
* .ENDM:                                 Macros.
* .EXITM:                                Macros.
* .EXPORT NAME:                          Other Commands.
* .FORM COL=COLS:                        Listings.
* .FORM LIN=LN:                          Listings.
* .FORM LIN=LN COL=COLS:                 Listings.
* .GLOBAL NAME:                          Other Commands.
* .HEADING STRING:                       Listings.
* .INCLUDE "STR":                        Other Commands.
* .INSTR("STRING", "SEG", IX):           String Builtins.
* .LEN("STR"):                           String Builtins.
* .MACRO MACNAME:                        Macros.
* .MACRO MACNAME MACARGS ...:            Macros.
* .ORG:                                  Other Commands.
* .PAGE:                                 Listings.
* .PRINT LIST:                           Listings.
* .PRINT NOLIST:                         Listings.
* .PROGRAM:                              Other Commands.
* .RADIX S:                              Other Commands.
* .RES COUNT:                            Uninitialized.
* .RES.B COUNT:                          Uninitialized.
* .RES.L COUNT:                          Uninitialized.
* .RES.W COUNT:                          Uninitialized.
* .SDATA "STR" ...:                      Initialized.
* .SDATAB REPEAT, "STR" ...:             Initialized.
* .SDATAC "STR" ...:                     Initialized.
* .SDATAZ "STR" ...:                     Initialized.
* .SRES COUNT:                           Uninitialized.
* .SRES.B COUNT:                         Uninitialized.
* .SRES.L COUNT:                         Uninitialized.
* .SRES.W COUNT:                         Uninitialized.
* .SRESC COUNT:                          Uninitialized.
* .SRESC.B COUNT:                        Uninitialized.
* .SRESC.L COUNT:                        Uninitialized.
* .SRESC.W COUNT:                        Uninitialized.
* .SRESZ COUNT:                          Uninitialized.
* .SRESZ.B COUNT:                        Uninitialized.
* .SRESZ.L COUNT:                        Uninitialized.
* .SRESZ.W COUNT:                        Uninitialized.
* .SUBSTR("STRING",START,LEN):           String Builtins.
* ; as comment char:                     Invoking GASP.
* \@:                                    Macros.
* absolute expressions:                  Expressions.
* argument fields:                       Syntax Details.
* avoiding preprocessing:                Markers.
* bang, as comment:                      Invoking GASP.
* breaking out of loops:                 Loops.
* comment character, changing:           Invoking GASP.
* comments:                              Markers.
* continuation character:                Markers.
* copying literally to output:           Markers.
* directive field:                       Syntax Details.
* EQ:                                    Conditionals.
* exclamation mark, as comment:          Invoking GASP.
* fields of GASP source line:            Syntax Details.
* GE:                                    Conditionals.
* GT:                                    Conditionals.
* INFILE ...:                            Invoking GASP.
* label field:                           Syntax Details.
* LE:                                    Conditionals.
* literal copy to output:                Markers.
* LOCAL NAME [ , ... ]:                  Macros.
* loops, breaking out of:                Loops.
* LT:                                    Conditionals.
* macros, count executed:                Macros.
* NAME .MACRO:                           Macros.
* NAME .MACRO ( MACARGS ... ):           Macros.
* NE:                                    Conditionals.
* number of macros executed:             Macros.
* preprocessing, avoiding:               Markers.
* PVAR .ASSIGN EXPR:                     Variables.
* PVAR .ASSIGNA AEXPR:                   Variables.
* PVAR .ASSIGNC "STR":                   Variables.
* PVAR .EQU EXPR:                        Variables.
* PVAR .REG (REGISTER):                  Variables.
* relocatable expressions:               Expressions.
* semicolon, as comment:                 Invoking GASP.
* shriek, as comment:                    Invoking GASP.
* symbol separator:                      Markers.
* symbols, separating from text:         Markers.
* text, separating from symbols:         Markers.
* whitespace:                            Syntax Details.



Tag Table:
Node: Top846
Node: Overview1280
Node: Invoking GASP2946
Node: Commands6682
Node: Conditionals7358
Node: Loops9650
Node: Variables11175
Node: Macros13570
Node: Data17532
Node: Initialized17980
Node: Uninitialized20259
Node: Listings21270
Node: Other Commands22466
Node: Syntax Details24218
Node: Markers25354
Node: Constants27602
Node: Symbols28804
Node: Expressions29100
Node: String Builtins30332
Node: Alternate31113
Node: Index32731

End Tag Table
