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Add info about cheap local names in macro local symbols.

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Kugel Fuhr
2025-07-07 12:05:46 +02:00
parent 29f7ab3809
commit b64c811a3f
1 changed files with 12 additions and 8 deletions
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doc/ca65.sgml
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@@ -918,6 +918,7 @@ See the description of the <tt><ref id=".PROC" name=".PROC"></tt>
directive for more information.
<label id=cheap-locals>
<sect1>Cheap local labels<p>
Cheap local labels are defined like standard labels, but the name of the
@@ -3751,20 +3752,23 @@ See: <tt><ref id=".ASCIIZ" name=".ASCIIZ"></tt>,<tt><ref id=".BYTE" name=".BYTE"
<sect1><tt>.LOCAL</tt><label id=".LOCAL"><p>
This command may only be used inside a macro definition. It declares a
list of identifiers as local to the macro expansion.
This command may only be used inside a macro definition. It declares a list
of identifiers as local to the macro expansion. The identifers may be
standard identifiers or cheap local identifiers depending on the planed use.
A problem when using macros are labels: Since they don't change their name,
you get a "duplicate symbol" error if the macro is expanded the second time.
Labels declared with <tt><ref id=".LOCAL" name=".LOCAL"></tt> have their
name mapped to an internal unique name (<tt/___ABCD__/) with each macro
name replaced by an internally generated unique name for each macro
invocation.
Some other assemblers start a new lexical block inside a macro expansion.
This has some drawbacks however, since that will not allow <em/any/ symbol
to be visible outside a macro, a feature that is sometimes useful. The
<tt><ref id=".LOCAL" name=".LOCAL"></tt> command is in my eyes a better way
to address the problem.
Please note that while the generated names are unique and guaranteed to not
clash with any user generated names, they are still regular symbols and
added to the current scope. This means that a local macro label will start a
new scope for cheap locals whenever the macro is expanded. To avoid that,
you may also use a <ref id="cheap-locals" name="cheap local symbol"> for the
name. In this case the assembler will generate unique cheap local
identifiers instead of standard ones.
You get an error when using <tt><ref id=".LOCAL" name=".LOCAL"></tt> outside
a macro.