223cc6685e
git-svn-id: svn://svn.compuextreme.de/Viitor/V963/Viitor_cc65@5933 504e572c-2e33-0410-9681-be2bf7408885
75 lines
3.0 KiB
HTML
75 lines
3.0 KiB
HTML
<!DOCTYPE HTML PUBLIC "-//W3C//DTD HTML 3.2 Final//EN">
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<HTML>
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<META NAME="GENERATOR" CONTENT="LinuxDoc-Tools 0.9.20">
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<TITLE>ld65 Users Guide: Detailed workings</TITLE>
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<LINK HREF="ld65-5.html" REL=next>
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<LINK HREF="ld65-3.html" REL=previous>
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<LINK HREF="ld65.html#toc4" REL=contents>
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<BODY>
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<A HREF="ld65-5.html">Next</A>
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<A HREF="ld65.html#toc4">Contents</A>
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<H2><A NAME="s4">4.</A> <A HREF="ld65.html#toc4">Detailed workings</A></H2>
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<P>The linker does several things when combining object modules:</P>
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<P>First, the command line is parsed from left to right. For each object file
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encountered (object files are recognized by a magic word in the header, so
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the linker does not care about the name), imported and exported
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identifiers are read from the file and inserted in a table. If a library
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name is given (libraries are also recognized by a magic word, there are no
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special naming conventions), all modules in the library are checked if an
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export from this module would satisfy an import from other modules. All
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modules where this is the case are marked. If duplicate identifiers are
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found, the linker issues a warning.</P>
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<P>This procedure (parsing and reading from left to right) does mean, that a
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library may only satisfy references for object modules (given directly or from
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a library) named <EM>before</EM> that library. With the command line</P>
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<P>
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<BLOCKQUOTE><CODE>
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<PRE>
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ld65 crt0.o clib.lib test.o
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<P>the module test.o may not contain references to modules in the library
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clib.lib. If this is the case, you have to change the order of the modules
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on the command line:</P>
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<P>
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<BLOCKQUOTE><CODE>
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<PRE>
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ld65 crt0.o test.o clib.lib
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</PRE>
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</CODE></BLOCKQUOTE>
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</P>
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<P>Step two is, to read the configuration file, and assign start addresses
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for the segments and define any linker symbols (see
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<A HREF="ld65-5.html#config-files">Configuration files</A>).</P>
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<P>After that, the linker is ready to produce an output file. Before doing that,
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it checks it's data for consistency. That is, it checks for unresolved
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externals (if the output format is not relocatable) and for symbol type
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mismatches (for example a zero page symbol is imported by a module as absolute
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symbol).</P>
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<P>Step four is, to write the actual target files. In this step, the linker will
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resolve any expressions contained in the segment data. Circular references are
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also detected in this step (a symbol may have a circular reference that goes
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unnoticed if the symbol is not used).</P>
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<P>Step five is to output a map file with a detailed list of all modules,
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segments and symbols encountered.</P>
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<P>And, last step, if you give the <CODE>
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<A HREF="ld65-2.html#option-v">-v</A></CODE> switch
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twice, you get a dump of the segment data. However, this may be quite
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unreadable if you're not a developer:-)</P>
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<HR>
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<A HREF="ld65-5.html">Next</A>
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