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author William Astle <lost@l-w.ca>
date Thu, 13 Jun 2013 22:12:35 -0600
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CLASS="SECTION"
><H1
CLASS="SECTION"
><A
NAME="AEN200"
>3.6. Assembler Directives</A
></H1
><P
>Various directives can be used to control the behaviour of the
assembler or to include non-code/data in the resulting output. Those directives
that are not described in detail in other sections of this document are
described below.</P
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN203"
>3.6.1. Data Directives</A
></H2
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>FCB <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .DB <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .BYTE <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
></DT
><DD
><P
>Include one or more constant bytes (separated by commas) in the output.</P
></DD
><DT
>FDB <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .DW <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .WORD <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
></DT
><DD
><P
>Include one or more words (separated by commas) in the output.</P
></DD
><DT
>FQB <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .QUAD <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
>, .4BYTE <CODE
CLASS="PARAMETER"
>expr[,...]</CODE
></DT
><DD
><P
>Include one or more double words (separated by commas) in the output.</P
></DD
><DT
>FCC <CODE
CLASS="PARAMETER"
>string</CODE
>, .ASCII <CODE
CLASS="PARAMETER"
>string</CODE
>, .STR <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>Include a string of text in the output. The first character of the operand
is the delimiter which must appear as the last character and cannot appear
within the string. The string is included with no modifications&#62;</P
></DD
><DT
>FCN <CODE
CLASS="PARAMETER"
>string</CODE
>, .ASCIZ <CODE
CLASS="PARAMETER"
>string</CODE
>, .STRZ <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>Include a NUL terminated string of text in the output. The first character of
the operand is the delimiter which must appear as the last character and
cannot appear within the string. A NUL byte is automatically appended to
the string.</P
></DD
><DT
>FCS <CODE
CLASS="PARAMETER"
>string</CODE
>, .ASCIS <CODE
CLASS="PARAMETER"
>string</CODE
>, .STRS <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>Include a string of text in the output with bit 7 of the final byte set. The
first character of the operand is the delimiter which must appear as the last
character and cannot appear within the string.</P
></DD
><DT
>ZMB <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Include a number of NUL bytes in the output. The number must be fully resolvable
during pass 1 of assembly so no forward or external references are permitted.</P
></DD
><DT
>ZMD <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Include a number of zero words in the output. The number must be fully
resolvable during pass 1 of assembly so no forward or external references are
permitted.</P
></DD
><DT
>ZMQ <CODE
CLASS="PARAMETER"
>expr<CODE
CLASS="PARAMETER"
></CODE
></CODE
></DT
><DD
><P
>Include a number of zero double-words in the output. The number must be fully
resolvable during pass 1 of assembly so no forward or external references are
permitted.</P
></DD
><DT
>RMB <CODE
CLASS="PARAMETER"
>expr</CODE
>, .BLKB <CODE
CLASS="PARAMETER"
>expr</CODE
>, .DS <CODE
CLASS="PARAMETER"
>expr</CODE
>, .RS <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Reserve a number of bytes in the output. The number must be fully resolvable
during pass 1 of assembly so no forward or external references are permitted.
The value of the bytes is undefined.</P
></DD
><DT
>RMD <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Reserve a number of words in the output. The number must be fully
resolvable during pass 1 of assembly so no forward or external references are
permitted. The value of the words is undefined.</P
></DD
><DT
>RMQ <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Reserve a number of double-words in the output. The number must be fully
resolvable during pass 1 of assembly so no forward or external references are
permitted. The value of the double-words is undefined.</P
></DD
><DT
>INCLUDEBIN <CODE
CLASS="PARAMETER"
>filename</CODE
></DT
><DD
><P
>Treat the contents of <CODE
CLASS="PARAMETER"
>filename</CODE
> as a string of bytes to
be included literally at the current assembly point. This has the same effect
as converting the file contents to a series of FCB statements and including
those at the current assembly point.</P
><P
> If <CODE
CLASS="PARAMETER"
>filename</CODE
> beings with a /, the file name
will be taken as absolute.  Otherwise, the current directory will be
searched followed by the search path in the order specified.</P
><P
> Please note that absolute path detection including drive letters will
not function correctly on Windows platforms.  Non-absolute inclusion will
work, however.</P
></DD
><DT
>FILL <CODE
CLASS="PARAMETER"
>size</CODE
>,<CODE
CLASS="PARAMETER"
>byte</CODE
></DT
><DD
><P
>Insert <CODE
CLASS="PARAMETER"
>size</CODE
> bytes of <CODE
CLASS="PARAMETER"
>byte</CODE
>.</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN314"
>3.6.2. Address Definition</A
></H2
><P
>The directives in this section all control the addresses of symbols
or the assembly process itself.</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>ORG <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Set the assembly address. The address must be fully resolvable on the
first pass so no external or forward references are permitted. ORG is not
permitted within sections when outputting to object files. For the DECB
target, each ORG directive after which output is generated will cause
a new preamble to be output. ORG is only used to determine the addresses
of symbols when the raw target is used.</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>sym</CODE
> EQU <CODE
CLASS="PARAMETER"
>expr</CODE
>, <CODE
CLASS="PARAMETER"
>sym</CODE
> = <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Define the value of <CODE
CLASS="PARAMETER"
>sym</CODE
> to be <CODE
CLASS="PARAMETER"
>expr</CODE
>.</P
></DD
><DT
><CODE
CLASS="PARAMETER"
>sym</CODE
> SET <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Define the value of <CODE
CLASS="PARAMETER"
>sym</CODE
> to be <CODE
CLASS="PARAMETER"
>expr</CODE
>.
Unlike EQU, SET permits symbols to be defined multiple times as long as SET
is used for all instances. Use of the symbol before the first SET statement
that sets its value is undefined.</P
></DD
><DT
>SETDP <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>Inform the assembler that it can assume the DP register contains
<CODE
CLASS="PARAMETER"
>expr</CODE
>. This directive is only advice to the assembler
to determine whether an address is in the direct page and has no effect
on the contents of the DP register. The value must be fully resolved during
the first assembly pass because it affects the sizes of subsequent instructions.</P
><P
>This directive has no effect in the object file target.</P
></DD
><DT
>ALIGN <CODE
CLASS="PARAMETER"
>expr</CODE
>[,<CODE
CLASS="PARAMETER"
>value</CODE
>]</DT
><DD
><P
>Force the current assembly address to be a multiple of
<CODE
CLASS="PARAMETER"
>expr</CODE
>.  If <CODE
CLASS="PARAMETER"
>value</CODE
> is not
specified, a series of NUL bytes is output to force the alignment, if
required.  Otherwise, the low order 8 bits of <CODE
CLASS="PARAMETER"
>value</CODE
>
will be used as the fill.  The alignment value must be fully resolved on the
first pass because it affects the addresses of subsquent instructions. 
However, <CODE
CLASS="PARAMETER"
>value</CODE
> may include forward references; as
long as it resolves to a constant for the second pass, the value will be
accepted.</P
><P
>Unless <CODE
CLASS="PARAMETER"
>value</CODE
> is specified as something like $12,
this directive is not suitable for inclusion in the middle of actual code. 
The default padding value is $00 which is intended to be used within data
blocks.  </P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN361"
>3.6.3. Conditional Assembly</A
></H2
><P
>Portions of the source code can be excluded or included based on conditions
known at assembly time. Conditionals can be nested arbitrarily deeply. The
directives associated with conditional assembly are described in this section.</P
><P
>All conditionals must be fully bracketed. That is, every conditional
statement must eventually be followed by an ENDC at the same level of nesting.</P
><P
>Conditional expressions are only evaluated on the first assembly pass.
It is not possible to game the assembly process by having a conditional
change its value between assembly passes. Due to the underlying architecture
of LWASM, there is no possible utility to IFP1 and IFP2, nor can they, as of LWASM 3.0, actually
be implemented meaningfully. Thus there is not and never will
be any equivalent of IFP1 or IFP2 as provided by other assemblers. Use of those opcodes
will throw a warning and be ignored.</P
><P
>It is important to note that if a conditional does not resolve to a constant
during the first parsing pass, an error will be thrown. This is unavoidable because the assembler
must make a decision about which source to include and which source to exclude at this stage.
Thus, expressions that work normally elsewhere will not work for conditions.</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>IFEQ <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to zero, the conditional
will be considered true.</P
></DD
><DT
>IFNE <CODE
CLASS="PARAMETER"
>expr</CODE
>, IF <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to a non-zero value, the conditional
will be considered true.</P
></DD
><DT
>IFGT <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to a value greater than zero, the conditional
will be considered true.</P
></DD
><DT
>IFGE <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to a value greater than or equal to zero, the conditional
will be considered true.</P
></DD
><DT
>IFLT <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to a value less than zero, the conditional
will be considered true.</P
></DD
><DT
>IFLE <CODE
CLASS="PARAMETER"
>expr</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>expr</CODE
> evaluates to a value less than or equal to zero , the conditional
will be considered true.</P
></DD
><DT
>IFDEF <CODE
CLASS="PARAMETER"
>sym</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>sym</CODE
> is defined at this point in the assembly
process, the conditional
will be considered true.</P
></DD
><DT
>IFNDEF <CODE
CLASS="PARAMETER"
>sym</CODE
></DT
><DD
><P
>If <CODE
CLASS="PARAMETER"
>sym</CODE
> is not defined at this point in the assembly
process, the conditional
will be considered true.</P
></DD
><DT
>ELSE</DT
><DD
><P
>If the preceding conditional at the same level of nesting was false, the
statements following will be assembled. If the preceding conditional at
the same level was true, the statements following will not be assembled.
Note that the preceding conditional might have been another ELSE statement
although this behaviour is not guaranteed to be supported in future versions
of LWASM.</P
></DD
><DT
>ENDC</DT
><DD
><P
>This directive marks the end of a conditional construct. Every conditional
construct must end with an ENDC directive.</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN426"
>3.6.4. OS9 Target Directives</A
></H2
><P
>This section includes directives that apply solely to the OS9
target.</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>OS9 <CODE
CLASS="PARAMETER"
>syscall</CODE
></DT
><DD
><P
>&#13;This directive generates a call to the specified system call. <CODE
CLASS="PARAMETER"
>syscall</CODE
> may be an arbitrary expression.&#13;</P
></DD
><DT
>MOD <CODE
CLASS="PARAMETER"
>size</CODE
>,<CODE
CLASS="PARAMETER"
>name</CODE
>,<CODE
CLASS="PARAMETER"
>type</CODE
>,<CODE
CLASS="PARAMETER"
>flags</CODE
>,<CODE
CLASS="PARAMETER"
>execoff</CODE
>,<CODE
CLASS="PARAMETER"
>datasize</CODE
></DT
><DD
><P
>&#13;This tells LWASM that the beginning of the actual module is here. It will
generate a module header based on the parameters specified.  It will also
begin calcuating the module CRC.&#13;</P
><P
>&#13;The precise meaning of the various parameters is beyond the scope of this
document since it is not a tutorial on OS9 module programming.&#13;</P
></DD
><DT
>EMOD</DT
><DD
><P
>&#13;This marks the end of a module and causes LWASM to emit the calculated CRC
for the module.&#13;</P
></DD
></DL
></DIV
></DIV
><DIV
CLASS="SECTION"
><H2
CLASS="SECTION"
><A
NAME="AEN451"
>3.6.5. Miscelaneous Directives</A
></H2
><P
>This section includes directives that do not fit into the other
categories.</P
><P
></P
><DIV
CLASS="VARIABLELIST"
><DL
><DT
>INCLUDE <CODE
CLASS="PARAMETER"
>filename</CODE
>, USE <CODE
CLASS="PARAMETER"
>filename</CODE
></DT
><DD
><P
> Include the contents of <CODE
CLASS="PARAMETER"
>filename</CODE
> at
this point in the assembly as though it were a part of the file currently
being processed.  Note that if whitespace appears in the name of the file,
you must enclose <CODE
CLASS="PARAMETER"
>filename</CODE
> in quotes.</P
><P
>Note that the USE variation is provided only for compatibility with other
assemblers. It is recommended to use the INCLUDE variation.</P
><P
>If <CODE
CLASS="PARAMETER"
>filename</CODE
> begins with a &quot;/&quot;, it is
interpreted as an absolute path. If it does not, the search path will be used
to find the file. First, the directory containing the file that contains this
directive. (Includes within an included file are relative to the included file,
not the file that included it.) If the file is not found there, the include path
is searched. If it is still not found, an error will be thrown. Note that the
current directory as understood by your shell or operating system is not searched.</P
></DD
><DT
>END <CODE
CLASS="PARAMETER"
>[expr]</CODE
></DT
><DD
><P
>This directive causes the assembler to stop assembling immediately as though
it ran out of input. For the DECB target only, <CODE
CLASS="PARAMETER"
>expr</CODE
>
can be used to set the execution address of the resulting binary. For all
other targets, specifying <CODE
CLASS="PARAMETER"
>expr</CODE
> will cause an error.</P
></DD
><DT
>ERROR <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>Causes a custom error message to be printed at this line. This will cause
assembly to fail. This directive is most useful inside conditional constructs
to cause assembly to fail if some condition that is known bad happens. Everything
from the directive to the end of the line is considered the error message.</P
></DD
><DT
>WARNING <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>Causes a custom warning message to be printed at this line. This will not cause
assembly to fail. This directive is most useful inside conditional constructs
or include files to alert the programmer to a deprecated feature being used
or some other condition that may cause trouble later, but which may, in fact,
not cause any trouble.</P
></DD
><DT
>.MODULE <CODE
CLASS="PARAMETER"
>string</CODE
></DT
><DD
><P
>This directive is ignored for most output targets. If the output target
supports encoding a module name into it, <CODE
CLASS="PARAMETER"
>string</CODE
>
will be used as the module name.</P
><P
>As of version 3.0, no supported output targets support this directive.</P
></DD
></DL
></DIV
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