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169 lines
5.2 KiB
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169 lines
5.2 KiB
Plaintext
<!doctype linuxdoc system>
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<article>
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<title>Using VICE with cc65
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<author>Ullrich von Bassewitz, <htmlurl url="mailto:uz@cc65.org" name="uz@cc65.org">
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<date>03.12.2000
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<abstract>
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How to debug your code using the VICE emulator.
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</abstract>
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<!-- Table of contents -->
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<toc>
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<!-- Begin the document -->
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<sect>Overview<p>
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This document describes how to debug your programs using the cc65 development
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tools and the VICE CBM emulator.
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<sect>What is VICE?<p>
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VICE is an emulator for many of the CBM machines. It runs on Unix, DOS and
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Windows 95. It emulates the Commodore 64, 128, VIC20, PET and the 600/700
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machines. For more information see the VICE home page:
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<htmlurl url="http://www.cs.cmu.edu/~dsladic/vice/vice.html"
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name="http://www.cs.cmu.edu/~dsladic/vice/vice.html">
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VICE has a builtin machine language monitor that may be used for debugging
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your programs. Using an emulator for debugging has some advantages:
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<itemize>
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<item>Since you're using a crossassembler/-compiler anyway, you don't need to
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transfer the program to the real machine until it is done.
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<item>An emulator allows many things that are almost impossible one of the
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original machines. You may set watchpoints (detect read or write access to
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arbitary addresses), debug interrupt handlers and even debug routines that run
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inside the 1541 floppy.
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<item>You may use the label file generated by the linker to make much more use
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from the monitor.
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</itemize>
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Please note that you need at least VICE version 0.16 for the label file
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feature to work. This version has still some problems (see <ref id="problems"
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name="Problems and workarounds">), but older versions had even more problems
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and do <em/not/ work correctly.
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<sect>How to prepare your programs<p>
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VICE support is mostly done via a label file that is generated by the linker
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and that may be read by the VICE monitor, so it knows about your program.
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Source level debugging is <tt/not/ available, you have to debug your programs
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in the assembler view.
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The first step is to generate object files that contain information about
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<em/all/ labels in your sources, not just the exported ones. This can be done
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by several means:
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<itemize>
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<item>Use the -g switch on the assembler command line.
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<item>Use the
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<tscreen><verb>
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.debuginfo +
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</verb></tscreen>
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command in your source.
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<item>Use the <tt/-g/ switch when invoking the compiler. The compiler will
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then place a <tt/.debuginfo/ command into the generated assembler source.
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</itemize>
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So, if you have just C code, all you need is to invoke the compiler with
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<tt/-g/. If you're using assembler code, you have to use <tt/-g/ for the
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assembler, or add "<tt/.debuginfo on/" to your source files. Since the
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generated debug info is not appended to the generated executables, it is a
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good idea to always use <tt/-g/. It makes the object files and libraries
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slightly larger (˜30%), but this is usually not a problem.
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The second step is to tell the linker that it should generate a VICE label
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file. This is done by the <tt/-Ln/ switch followed by the name of the label
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file (I'm usually using a <tt/.lbl/ extension for these files). An example for
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a linker command line would be:
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<tscreen><verb>
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ld65 -t c64 -Ln hello.lbl -m hello.map -o hello crt0 hello.o c64.lib
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</verb></tscreen>
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This will generate a file named hello.lbl that contains all symbols used in
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your program.
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<bf>Note</bf>: The runtime libraries and startup files were generated with
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debug info, so you don't have to care about this.
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<sect>How to use the label file<p>
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Load your program, then enter the monitor and use the "<tt/ll/" command to
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load your label file like this:
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<tscreen><verb>
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ll "hello.lbl"
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</verb></tscreen>
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You will get lots of warnings and even a few errors. You may ignore safely all
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these warnings and errors as long as they reference any problems VICE thinks
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it has with the labels.
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After loading the labels, they are used by VICE in the disassembler listing,
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and you may use them whereever you need to specify an address. Try
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<tscreen><verb>
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d ._main
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</verb></tscreen>
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as an example (note that VICE needs a leading dot before all labels, and that
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the compiler prepends an underline under most named labels).
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<sect>Problems and workarounds<label id="problems"><p>
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Older versions of VICE had several problems with labels. However, even those
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versions were still tremendously useful, and all known problems are gone in
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current versions. So, here is a list of the problems known to me as of version
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0.16.1:
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<itemize>
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<item>The "<tt/ll/" command does not work. Worse, it seems that internal
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memory gets corrupted when using this command, so VICE will crash after use.
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Use the "<tt/pb/" command to load the label file in this case.
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<item>VICE will crash if you use a label that is undefined. This is probably
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the worst problem of all, since it needs just one typo to kill VICE. So, watch
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your steps:-)
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<item>Cheap labels, that is, labels starting with '@' or '?' are not accepted.
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<item>The disassembly output is somewhat suboptimal. However, most things are
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just cosmetical, e.g. labels appended to the right side of the disassembled
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code.
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</itemize>
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<bf>Note</bf>: All these problems are fixed in current (>= 1.0) VICE
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versions. If you're really using such an old version, you should think about
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an upgrade.
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</article>
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