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| <title>Using as: MMIX-Symbols</title> |
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| Next: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="n" rel="next">MMIX-Regs</a>, Previous: <a href="MMIX_002dChars.html#MMIX_002dChars" accesskey="p" rel="prev">MMIX-Chars</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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| <a name="Symbols-4"></a> |
| <h4 class="subsubsection">9.28.3.2 Symbols</h4> |
| <p>The character ‘<samp>:</samp>’ is permitted in identifiers. There are two |
| exceptions to it being treated as any other symbol character: if a symbol |
| begins with ‘<samp>:</samp>’, it means that the symbol is in the global namespace |
| and that the current prefix should not be prepended to that symbol |
| (see <a href="MMIX_002dPseudos.html#MMIX_002dprefix">MMIX-prefix</a>). The ‘<samp>:</samp>’ is then not considered part of the |
| symbol. For a symbol in the label position (first on a line), a ‘<samp>:</samp>’ |
| at the end of a symbol is silently stripped off. A label is permitted, |
| but not required, to be followed by a ‘<samp>:</samp>’, as with many other |
| assembly formats. |
| </p> |
| <p>The character ‘<samp>@</samp>’ in an expression, is a synonym for ‘<samp>.</samp>’, the |
| current location. |
| </p> |
| <p>In addition to the common forward and backward local symbol formats |
| (see <a href="Symbol-Names.html#Symbol-Names">Symbol Names</a>), they can be specified with upper-case ‘<samp>B</samp>’ and |
| ‘<samp>F</samp>’, as in ‘<samp>8B</samp>’ and ‘<samp>9F</samp>’. A local label defined for the |
| current position is written with a ‘<samp>H</samp>’ appended to the number: |
| </p><div class="smallexample"> |
| <pre class="smallexample">3H LDB $0,$1,2 |
| </pre></div> |
| <p>This and traditional local-label formats cannot be mixed: a label must be |
| defined and referred to using the same format. |
| </p> |
| <p>There’s a minor caveat: just as for the ordinary local symbols, the local |
| symbols are translated into ordinary symbols using control characters are |
| to hide the ordinal number of the symbol. Unfortunately, these symbols |
| are not translated back in error messages. Thus you may see confusing |
| error messages when local symbols are used. Control characters |
| ‘<samp>\003</samp>’ (control-C) and ‘<samp>\004</samp>’ (control-D) are used for the |
| MMIX-specific local-symbol syntax. |
| </p> |
| <p>The symbol ‘<samp>Main</samp>’ is handled specially; it is always global. |
| </p> |
| <p>By defining the symbols ‘<samp>__.MMIX.start..text</samp>’ and |
| ‘<samp>__.MMIX.start..data</samp>’, the address of respectively the ‘<samp>.text</samp>’ |
| and ‘<samp>.data</samp>’ segments of the final program can be defined, though when |
| linking more than one object file, the code or data in the object file |
| containing the symbol is not guaranteed to be start at that position; just |
| the final executable. See <a href="MMIX_002dPseudos.html#MMIX_002dloc">MMIX-loc</a>. |
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| Next: <a href="MMIX_002dRegs.html#MMIX_002dRegs" accesskey="n" rel="next">MMIX-Regs</a>, Previous: <a href="MMIX_002dChars.html#MMIX_002dChars" accesskey="p" rel="prev">MMIX-Chars</a>, Up: <a href="MMIX_002dSyntax.html#MMIX_002dSyntax" accesskey="u" rel="up">MMIX-Syntax</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="AS-Index.html#AS-Index" title="Index" rel="index">Index</a>]</p> |
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