gasp.html

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<H3><A NAME="SEC10" HREF="gasp_toc.html#TOC10">Uninitialized data</A></H3>

<P>
Use the <CODE>.RES</CODE>, <CODE>.SRES</CODE>, <CODE>.SRESC</CODE>, and <CODE>.SRESZ</CODE>
directives to reserve memory and leave it uninitialized.  GASP
resolves these directives to appropriate calls of the GNU
<CODE>as</CODE> <CODE>.space</CODE> directive.

</P>
<DL COMPACT>

<DT><CODE>.RES <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX74"></A>
<DT><CODE>.RES.B <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX75"></A>
<DT><CODE>.RES.W <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX76"></A>
<DT><CODE>.RES.L <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX77"></A>
Reserve room for <VAR>count</VAR> uninitialized elements of data.  The
suffix specifies the size of each element: <CODE>.RES.B</CODE> reserves
<VAR>count</VAR> bytes, <CODE>.RES.W</CODE> reserves <VAR>count</VAR> pairs of bytes,
and <CODE>.RES.L</CODE> reserves <VAR>count</VAR> quartets.  <CODE>.RES</CODE> without a
suffix is equivalent to <CODE>.RES.L</CODE>.

<DT><CODE>.SRES <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX78"></A>
<DT><CODE>.SRES.B <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX79"></A>
<DT><CODE>.SRES.W <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX80"></A>
<DT><CODE>.SRES.L <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX81"></A>
<CODE>.SRES</CODE> is a synonym for <SAMP>`.RES'</SAMP>.

<DT><CODE>.SRESC <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX82"></A>
<DT><CODE>.SRESC.B <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX83"></A>
<DT><CODE>.SRESC.W <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX84"></A>
<DT><CODE>.SRESC.L <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX85"></A>
Like <CODE>.SRES</CODE>, but reserves space for <CODE><VAR>count</VAR>+1</CODE> elements.

<DT><CODE>.SRESZ <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX86"></A>
<DT><CODE>.SRESZ.B <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX87"></A>
<DT><CODE>.SRESZ.W <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX88"></A>
<DT><CODE>.SRESZ.L <VAR>count</VAR></CODE>
<DD>
<A NAME="IDX89"></A>
Like <CODE>.SRES</CODE>, but reserves space for <CODE><VAR>count</VAR>+1</CODE> elements.
</DL>



<H2><A NAME="SEC11" HREF="gasp_toc.html#TOC11">Assembly listing control</A></H2>

<P>
The GASP listing-control directives correspond to
related GNU <CODE>as</CODE> directives.

</P>
<DL COMPACT>

<DT><CODE>.PRINT LIST</CODE>
<DD>
<A NAME="IDX90"></A>
<DT><CODE>.PRINT NOLIST</CODE>
<DD>
<A NAME="IDX91"></A>
Print control.  This directive emits the GNU <CODE>as</CODE> directive
<CODE>.list</CODE> or <CODE>.nolist</CODE>, according to its argument.  See section `<CODE>.list</CODE>' in <CITE>Using as</CITE>, for details on how these directives
interact.

<DT><CODE>.FORM LIN=<VAR>ln</VAR></CODE>
<DD>
<A NAME="IDX92"></A>
<DT><CODE>.FORM COL=<VAR>cols</VAR></CODE>
<DD>
<A NAME="IDX93"></A>
<DT><CODE>.FORM LIN=<VAR>ln</VAR> COL=<VAR>cols</VAR></CODE>
<DD>
<A NAME="IDX94"></A>
Specify the page size for assembly listings: <VAR>ln</VAR> represents the
number of lines, and <VAR>cols</VAR> 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 <CODE>.FORM</CODE>
do <EM>not</EM> carry over as defaults.)  Emits the <CODE>.psize</CODE>
assembler directive.

<DT><CODE>.HEADING <VAR>string</VAR></CODE>
<DD>
<A NAME="IDX95"></A>
Specify <VAR>string</VAR> as the title of your assembly listings.  Emits
<SAMP>`.title "<VAR>string</VAR>"'</SAMP>.

<DT><CODE>.PAGE</CODE>
<DD>
<A NAME="IDX96"></A>
Force a new page in assembly listings.  Emits <SAMP>`.eject'</SAMP>.
</DL>



<H2><A NAME="SEC12" HREF="gasp_toc.html#TOC12">Miscellaneous commands</A></H2>

<DL COMPACT>

<DT><CODE>.ALTERNATE</CODE>
<DD>
<A NAME="IDX97"></A>
Use the alternate macro syntax henceforth in the assembly.
See section <A HREF="gasp.html#SEC19">Alternate macro syntax</A>.

<DT><CODE>.ORG</CODE>
<DD>
<A NAME="IDX98"></A>
This command is recognized, but not yet implemented.  GASP
generates an error message for programs that use <CODE>.ORG</CODE>.

<DT><CODE>.RADIX <VAR>s</VAR></CODE>
<DD>
<A NAME="IDX99"></A>
GASP understands numbers in any of base two, eight, ten, or
sixteen.  You can encode the base explicitly in any numeric constant
(see section <A HREF="gasp.html#SEC15">String and numeric constants</A>).  If you write
numbers without an explicit indication of the base, the most recent
<SAMP>`.RADIX <VAR>s</VAR>'</SAMP> command determines how they are interpreted.
<VAR>s</VAR> is a single letter, one of the following:

<DL COMPACT>

<DT><CODE>.RADIX B</CODE>
<DD>
Base 2.

<DT><CODE>.RADIX Q</CODE>
<DD>
Base 8.

<DT><CODE>.RADIX D</CODE>
<DD>
Base 10.  This is the original default radix.

<DT><CODE>.RADIX H</CODE>
<DD>
Base 16.
</DL>

You may specify the argument <VAR>s</VAR> in lower case (any of <SAMP>`bqdh'</SAMP>)
with the same effects.

<DT><CODE>.EXPORT <VAR>name</VAR></CODE>
<DD>
<A NAME="IDX100"></A>
<DT><CODE>.GLOBAL <VAR>name</VAR></CODE>
<DD>
<A NAME="IDX101"></A>
Declare <VAR>name</VAR> global (emits <SAMP>`.global <VAR>name</VAR>'</SAMP>).  The two
directives are synonymous.

<DT><CODE>.PROGRAM</CODE>
<DD>
<A NAME="IDX102"></A>
No effect: GASP accepts this directive, and silently ignores it.

<DT><CODE>.END</CODE>
<DD>
<A NAME="IDX103"></A>
Mark end of each preprocessor file.  GASP issues a warning if it
reaches end of file without seeing this command.

<DT><CODE>.INCLUDE "<VAR>str</VAR>"</CODE>
<DD>
<A NAME="IDX104"></A>
Preprocess the file named by <VAR>str</VAR>, as if its contents appeared
where the <CODE>.INCLUDE</CODE> directive does.  GASP imposes a maximum
limit of 30 stacked include files, as a sanity check.

<DT><CODE>.ALIGN <VAR>size</VAR></CODE>
<DD>
<A NAME="IDX105"></A>
Evaluate the absolute expression <VAR>size</VAR>, and emit the assembly
instruction <SAMP>`.align <VAR>size</VAR>'</SAMP> using the result.
</DL>



<H2><A NAME="SEC13" HREF="gasp_toc.html#TOC13">Details of the GASP syntax</A></H2>

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

</P>
<P>
<A NAME="IDX106"></A>
<EM>Whitespace</EM> (blanks or tabs; <EM>not</EM> 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.

</P>
<P>
<A NAME="IDX107"></A>
<A NAME="IDX108"></A>
The <EM>first field</EM>, an optional <EM>label</EM>, 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).

</P>
<P>
<A NAME="IDX109"></A>
The <EM>second field</EM>, which must appear after some whitespace,
contains a GASP or assembly <EM>directive</EM>.

</P>
<P>
<A NAME="IDX110"></A>
Any <EM>further fields</EM> on a line are <EM>arguments</EM> to the
directive; you can separate them from one another using either commas or
whitespace.

</P>



<H3><A NAME="SEC14" HREF="gasp_toc.html#TOC14">Special syntactic markers</A></H3>

<P>
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, <SAMP>`\@'</SAMP>, works only within macro definitions;
see section <A HREF="gasp.html#SEC7">Defining your own directives</A>.)

</P>
<P>
<A NAME="IDX111"></A>
The trailing part of any GASP source line may be a <EM>comment</EM>.
A comment begins with the first unquoted comment character (<SAMP>`!'</SAMP> by
default), or an escaped or doubled comment character (<SAMP>`\!'</SAMP> or
<SAMP>`!!'</SAMP> by default), and extends to the end of a line.  You can
specify what comment character to use with the <SAMP>`-c'</SAMP> option
(see section <A HREF="gasp.html#SEC2">Command Line Options</A>).  The two kinds of
comment markers lead to slightly different treatment:

</P>
<DL COMPACT>

<DT><CODE>!</CODE>
<DD>
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 <CODE>.ASSIGNA</CODE> or
<CODE>.ASSIGNC</CODE>) present.  For example, a macro that begins like this


<PRE>
        .MACRO  SUM FROM=0, TO=9
        ! \FROM \TO
</PRE>

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

<DT><CODE>\!</CODE>
<DD>
<DT><CODE>!!</CODE>
<DD>
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.
</DL>

<P>
<A NAME="IDX112"></A>
<A NAME="IDX113"></A>
To <EM>continue a statement</EM> on the next line of the file, begin the
second line with the character <SAMP>`+'</SAMP>.

</P>
<P>
<A NAME="IDX114"></A>
<A NAME="IDX115"></A>
<A NAME="IDX116"></A>
<A NAME="IDX117"></A>
Occasionally you may want to prevent GASP from preprocessing some
particular bit of text.  To <EM>copy literally</EM> from the GASP
source to its output, place <SAMP>`\('</SAMP> before the string to copy, and
<SAMP>`)'</SAMP> at the end.  For example, write <SAMP>`\(\!)'</SAMP> if you need the
characters <SAMP>`\!'</SAMP> in your assembly output.

</P>
<P>
<A NAME="IDX118"></A>
<A NAME="IDX119"></A>
<A NAME="IDX120"></A>
To <EM>separate a preprocessor variable</EM> from text to appear
immediately after its value, write a single quote (<CODE>'</CODE>).  For
example, <SAMP>`.SDATA "\P'1"'</SAMP> writes a string built by concatenating the
value of <CODE>P</CODE> and the digit <SAMP>`1'</SAMP>.  (You cannot achieve this by
writing just <SAMP>`\P1'</SAMP>, since <SAMP>`P1'</SAMP> is itself a valid name for a
preprocessor variable.)

</P>


<H3><A NAME="SEC15" HREF="gasp_toc.html#TOC15">String and numeric constants</A></H3>

<P>
There are two ways of writing <EM>string constants</EM> in GASP: as
literal text, and by numeric byte value.  Specify a string literal
between double quotes (<CODE>"<VAR>str</VAR>"</CODE>).  Specify an individual
numeric byte value as an absolute expression between angle brackets
(<CODE>&#60;<VAR>expr</VAR>&#62;</CODE>.  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; see section <A HREF="gasp.html#SEC19">Alternate macro syntax</A>.)

</P>
<P>
You can write <EM>numeric constants</EM> either in a specific base, or in
whatever base is currently selected (either 10, or selected by the most
recent <CODE>.RADIX</CODE>).

</P>
<P>
To write a number in a <EM>specific base</EM>, use the pattern
<CODE><VAR>s</VAR>'<VAR>ddd</VAR></CODE>: a base specifier character <VAR>s</VAR>, followed
by a single quote followed by digits <VAR>ddd</VAR>.  The base specifier
character matches those you can specify with <CODE>.RADIX</CODE>: <SAMP>`B'</SAMP> for
base 2, <SAMP>`Q'</SAMP> for base 8, <SAMP>`D'</SAMP> for base 10, and <SAMP>`H'</SAMP> for base
16.  (You can write this character in lower case if you prefer.)

</P>



<H3><A NAME="SEC16" HREF="gasp_toc.html#TOC16">Symbols</A></H3>

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

</P>


<H3><A NAME="SEC17" HREF="gasp_toc.html#TOC17">Arithmetic expressions in GASP</A></H3>

<P>
<A NAME="IDX121"></A>
<A NAME="IDX122"></A>
There are two kinds of expressions, depending on their result:
<EM>absolute</EM> expressions, which resolve to a constant (that is, they
do not involve any values unknown to GASP), and <EM>relocatable</EM>
expressions, which must reduce to the form

</P>

<PRE>
<VAR>addsym</VAR>+<VAR>const</VAR>-<VAR>subsym</VAR>
</PRE>

<P>