2021-01-21 13:40:28 +01:00
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2024-09-06 12:39:30 +02:00
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<title>doc/book/techniques/errors</title>
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2021-01-21 13:40:28 +01:00
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</head><body>
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<p><span class="h1">Errors</span>
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<br/><br/>
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RETRO does only minimal error checking.
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<br/><br/>
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<span class="h2">Non-Fatal</span>
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<br/><br/>
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A non-fatal error will be reported on <strong>word not found</strong> during
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interactive or compile time. Note that this only applies to
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calls: if you try to get a pointer to an undefined word, the
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returned pointer will be zero.
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<br/><br/>
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<span class="h2">Fatal</span>
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<br/><br/>
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A number of conditions are known to cause fatal errors. The
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main ones are stack overflow, stack underflow, and division
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by zero.
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<br/><br/>
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On these, RETRO will generally exit. For stack depth issues,
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the VM will attempt to display an error prior to exiting.
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<br/><br/>
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In some cases, the VM may get stuck in an endless loop. If this
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occurs, try using CTRL+C to kill the process, or kill it using
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whatever means your host system provides.
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<br/><br/>
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<span class="h2">Rationale</span>
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<br/><br/>
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Error checks are useful, but slow - especially on a minimal
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system like RETRO. The overhead of doing depth or other checks
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adds up quickly.
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<br/><br/>
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As an example, adding a depth check to <span class="tt">drop</span> increases the
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time to use it 250,000 times in a loop from 0.16 seconds to
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1.69 seconds.
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<br/><br/>
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</p>
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</body></html>
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