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Document the new ubiquitous_idents feature

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git-svn-id: svn://svn.cc65.org/cc65/trunk@2982 b7a2c559-68d2-44c3-8de9-860c34a00d81
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cuz 2004-04-20 12:54:21 +00:00
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doc/ca65.sgml
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@ -909,7 +909,58 @@ if you want to access the "other" symbol <tt/bar/, you would have to write:
</verb></tscreen> </verb></tscreen>
<sect>Address sizes<label id="address-sizes"><p> <sect>Address sizes and memory models<label id="address-sizes"><p>
<sect1>Address sizes<p>
ca65 assigns each segment and each symbol an address size. This is true, even
if the symbol is not used as an address. You may also think of a value range
of the symbol instead of an address size.
Possible address sizes are:
<itemize>
<item>Zeropage or direct (8 bits)
<item>Absolute (16 bits)
<item>Far (24 bits)
<item>Long (32 bits)
<itemize>
Since the assembler uses default address sizes for the segments and symbols,
it is usually not necessary to override the default behaviour. In cases, where
it is necessary, the following keywords may be used to specify address sizes:
<itemize>
<item>DIRECT, ZEROPAGE or ZP for zeropage addressing (8 bits).
<item>ABSOLUTE, ABS or NEAR for absolute addressing (16 bits).
<item>FAR for far addressing (24 bits).
<item>LONG or DWORD for long addressing (32 bits).
<itemize>
<sect1>Address sizes of segments<p>
The assembler assigns an address size to each segment. Since the
representation of a label within this segment is "segment start + offset",
labels will inherit the address size of the segment they are declared in.
The address size of a segment may be changed, by using an optional address
size modifier. See the <tt/<ref id=".SEGMENT" name="segment directive">/ for
an explanation on how this is done.
<sect1>Address sizes of symbols<p>
<sect1>Memory models<p>
The default address size of a segment depends on the memory model used. Since
labels inherit the address size from the segment they are declared in,
changing the memory model is an easy way to change the address size of many
symbols at once.
@ -2025,27 +2076,6 @@ Here's a list of all control commands and a description, what they do:
<descrip> <descrip>
<tag><tt>dollar_is_pc</tt></tag>
The dollar sign may be used as an alias for the star (`*'), which
gives the value of the current PC in expressions.
Note: Assignment to the pseudo variable is not allowed.
<tag><tt>labels_without_colons</tt></tag>
Allow labels without a trailing colon. These labels are only accepted,
if they start at the beginning of a line (no leading white space).
<tag><tt>loose_string_term</tt></tag>
Accept single quotes as well as double quotes as terminators for string
constants.
<tag><tt>loose_char_term</tt></tag>
Accept single quotes as well as double quotes as terminators for char
constants.
<tag><tt>at_in_identifiers</tt></tag> <tag><tt>at_in_identifiers</tt></tag>
Accept the at character (`@') as a valid character in identifiers. The Accept the at character (`@') as a valid character in identifiers. The
@ -2058,6 +2088,17 @@ Here's a list of all control commands and a description, what they do:
at character is not allowed to start an identifier, even with this at character is not allowed to start an identifier, even with this
feature enabled. feature enabled.
<tag><tt>dollar_is_pc</tt></tag>
The dollar sign may be used as an alias for the star (`*'), which
gives the value of the current PC in expressions.
Note: Assignment to the pseudo variable is not allowed.
<tag><tt>labels_without_colons</tt></tag>
Allow labels without a trailing colon. These labels are only accepted,
if they start at the beginning of a line (no leading white space).
<tag><tt>leading_dot_in_identifiers</tt></tag> <tag><tt>leading_dot_in_identifiers</tt></tag>
Accept the dot (`.') as the first character of an identifier. This may be Accept the dot (`.') as the first character of an identifier. This may be
@ -2067,13 +2108,15 @@ Here's a list of all control commands and a description, what they do:
overridden. When using this feature, you may also get into trouble if overridden. When using this feature, you may also get into trouble if
later versions of the assembler define new keywords starting with a dot. later versions of the assembler define new keywords starting with a dot.
<tag><tt>pc_assignment</tt></tag> <tag><tt>loose_char_term</tt></tag>
Allow assignments to the PC symbol (`*' or `&dollar;' if <tt/dollar_is_pc/ Accept single quotes as well as double quotes as terminators for char
is enabled). Such an assignment is handled identical to the <tt><ref constants.
id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
removing the lines with the assignments may also be an option when porting <tag><tt>loose_string_term</tt></tag>
code written for older assemblers).
Accept single quotes as well as double quotes as terminators for string
constants.
<tag><tt>missing_char_term</tt></tag> <tag><tt>missing_char_term</tt></tag>
@ -2085,6 +2128,21 @@ Here's a list of all control commands and a description, what they do:
<bf/Note:/ This does not work in conjunction with <tt/.FEATURE <bf/Note:/ This does not work in conjunction with <tt/.FEATURE
loose_string_term/, since in this case the input would be ambigous. loose_string_term/, since in this case the input would be ambigous.
<tag><tt>pc_assignment</tt></tag>
Allow assignments to the PC symbol (`*' or `&dollar;' if <tt/dollar_is_pc/
is enabled). Such an assignment is handled identical to the <tt><ref
id=".ORG" name=".ORG"></tt> command (which is usually not needed, so just
removing the lines with the assignments may also be an option when porting
code written for older assemblers).
<tag><tt>ubiquitous_idents</tt></tag>
Allow the use of instructions names as names for macros and symbols. This
makes it possible to "overload" instructions by defining a macro with the
same name. This does also make it possible to introduce hard to find errors
in your code, so be careful!
</descrip> </descrip>
It is also possible to specify features on the command line using the It is also possible to specify features on the command line using the
@ -2823,33 +2881,35 @@ Here's a list of all control commands and a description, what they do:
(and up to 65534 per executable). There are shortcut commands for (and up to 65534 per executable). There are shortcut commands for
the most common segments ("CODE", "DATA" and "BSS"). the most common segments ("CODE", "DATA" and "BSS").
The command is followed by a string containing the segment name (there The command is followed by a string containing the segment name (there are
are some constraints for the name - as a rule of thumb use only those some constraints for the name - as a rule of thumb use only those segment
segment names that would also be valid identifiers). There may also be names that would also be valid identifiers). There may also be an optional
an optional attribute separated by a comma. Valid attributes are address size separated by a colon. See the section covering <tt/<ref
"<tt/zeropage/" and "<tt/absolute/". id="address-sizes" name="address sizes">/ for more information.
When specifying a segment for the first time, "absolute" is the The default address size for a segment depends on the memory model specified
default. For all other uses, the attribute specified the first time on the command line. The default is "absolute", which means that you don't
is the default. have to use an address size modifier in most cases.
"absolute" means that this is a segment with absolute addressing. That "absolute" means that the is a segment with 16 bit (absolute) addressing.
is, the segment will reside somewhere in core memory outside the zero That is, the segment will reside somewhere in core memory outside the zero
page. "zeropage" means the opposite: The segment will be placed in the page. "zeropage" (8 bit) means that the segment will be placed in the zero
zero page and direct (short) addressing is possible for data in this page and direct (short) addressing is possible for data in this segment.
segment.
Beware: Only labels in a segment with the zeropage attribute are marked Beware: Only labels in a segment with the zeropage attribute are marked
as reachable by short addressing. The `*' (PC counter) operator will as reachable by short addressing. The `*' (PC counter) operator will
work as in other segments and will create absolute variable values. work as in other segments and will create absolute variable values.
Example: Please note that a segment cannot have two different address sizes. A
segment specified as zeropage cannot be declared as being absolute later.
Examples:
<tscreen><verb> <tscreen><verb>
.segment "ROM2" ; Switch to ROM2 segment .segment "ROM2" ; Switch to ROM2 segment
.segment "ZP2", zeropage ; New direct segment .segment "ZP2": zeropage ; New direct segment
.segment "ZP2" ; Ok, will use last attribute .segment "ZP2" ; Ok, will use last attribute
.segment "ZP2", absolute ; Error, redecl mismatch .segment "ZP2": absolute ; Error, redecl mismatch
</verb></tscreen> </verb></tscreen>
See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE" See: <tt><ref id=".BSS" name=".BSS"></tt>, <tt><ref id=".CODE"