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diff --git a/.html/dev/debugger-101.html b/.html/dev/debugger-101.html deleted file mode 100644 index a19476a..0000000 --- a/.html/dev/debugger-101.html +++ /dev/null @@ -1,178 +0,0 @@ -<!DOCTYPE html> -<html> -<head> - <title> - The Codex » - Intro to Debuggers - </title> - - <link - rel='stylesheet' - type='text/css' - href='http://fonts.googleapis.com/css?family=Buenard:400,700&subset=latin,latin-ext'> - <link - rel="stylesheet" - type="text/css" - href="../media/css/reset.css"> - <link - rel="stylesheet" - type="text/css" - href="../media/css/grimoire.css"> -</head> -<body> - -<div id="shell"> - - <ol id="breadcrumbs"> - - <li class="crumb-0 not-last"> - - <a href="../">index</a> - - </li> - - <li class="crumb-1 not-last"> - - <a href="./">dev</a> - - </li> - - <li class="crumb-2 last"> - - debugger-101 - - </li> - - </ol> - - - - <div id="article"> - <h1 id="intro-to-debuggers">Intro to Debuggers</h1> -<p>(Written largely because newbies in <a href="http://evanchooly.com">##java</a> never seem -to have this knowledge.)</p> -<p>A “debugger” is a mechanism for monitoring and controlling the execution of -your program, usually interactively. Using a debugger, you can stop your -program at known locations and examine the <em>actual</em> values of its variables -(to compare against what you expected), monitor variables for changes (to see -where they got the values they have, and why), and step through code a line at -a time (to watch control flow and verify that it matches your expectations).</p> -<p>Pretty much every worthwhile language has debugging support of some kind, -whether it's via IDE integration or via a command-line debugger.</p> -<p>(Of course, none of this helps if you don't have a mental model of the -“expected” behaviour of the program. Debuggers can help you read, but can't -replace having an understanding of the code.)</p> -<h2 id="debugging-your-first-program">Debugging Your First Program</h2> -<p>Generally, you start running a debugger because you have a known problem -- an -exception, or code behaving strangely -- somewhere in your program that you -want to investigate more closely. Start by setting a <em>breakpoint</em> in your -program at a statement slightly before the problem area.</p> -<p>Breakpoints are instructions to the debugger, telling it to stop execution -when the program reaches the statement the breakpoint is set on.</p> -<p>Run the program in the debugger. When it reaches your breakpoint, execution -will stop (and your program will freeze, rather than exiting). You can now -<em>inspect</em> values and run expressions in the context of your program in its -current state. Depending on the debugger and the platform, you may be able to -modify those values, too, to quickly experiment with the problem and attempt -to solve it.</p> -<p>Once you've looked at the relevant variables, you can resume executing your -program - generally in one of five ways:</p> -<ul> -<li> -<p><em>Continue</em> execution normally. The debugger steps aside until the program - reaches the next breakpoint, or exits, and your program executes normally.</p> -</li> -<li> -<p>Execute the <em>next</em> statement. Execution proceeds for one statement in the - current function, then stops again. If the statement is, for example, a - function or method call, the call will be completely evaluated (unless it - contains breakpoints of its own). (In some debuggers, this is labelled “step - over,” since it will step “over” a function call.)</p> -</li> -<li> -<p><em>Step</em> forward one operation. Execution proceeds for one statement, then - stops again. This mode can single-step into function calls, rather than - letting them complete uninterrupted.</p> -</li> -<li> -<p><em>Continue to end of function</em>. The debugger steps aside until the program - reaches the end of the current function, then halts the program again.</p> -</li> -<li> -<p><em>Continue to a specific statement</em>. Some debuggers support this mode as a - way of stepping over or through “uninteresting” sections of code quickly and - easily. (You can implement this yourself with “Continue” and normal - breakpoints, too.)</p> -</li> -</ul> -<p>Whenever the debugger halts your program, you can do any of several things:</p> -<ul> -<li> -<p>Inspect the value of a variable or field, printing a useful representation - to the debugger. This is a more flexible version of the basic idea of - printing debug output as you go: because the program is stopped, you can - pick and choose which bits of information to look at on the fly, rather than - having to rerun your code with extra debug output.</p> -</li> -<li> -<p>Inspect the result of an expression. The debugger will evaluate an - expression “as if” it occurred at the point in the program where the - debugger is halted, including any local variables. In languages with static - visibility controls like Java, visibility rules are often relaxed in the - name of ease of use, allowing you to look at the private fields of objects. - The result of the expression will be made available for inspection, just - like a variable.</p> -</li> -<li> -<p>Modify a variable or field. You can use this to quickly test hypotheses: for - example, if you know what value a variable “should” have, you can set that - value directly and observe the behaviour of the program to check that it - does what you expected before fixing the code that sets the variable in a - non-debug run.</p> -</li> -<li> -<p>In some debuggers, you can run arbitrary code in the context of the halted - program.</p> -</li> -<li> -<p>Abort the program.</p> -</li> -</ul> - </div> - - - -<div id="comments"> -<div id="disqus_thread"></div> -<script type="text/javascript"> - /* * * CONFIGURATION VARIABLES: EDIT BEFORE PASTING INTO YOUR WEBPAGE * * */ - var disqus_shortname = 'grimoire'; // required: replace example with your forum shortname - - /* * * DON'T EDIT BELOW THIS LINE * * */ - (function() { - var dsq = document.createElement('script'); dsq.type = 'text/javascript'; dsq.async = true; - dsq.src = 'http://' + disqus_shortname + '.disqus.com/embed.js'; - (document.getElementsByTagName('head')[0] || document.getElementsByTagName('body')[0]).appendChild(dsq); - })(); -</script> -<noscript>Please enable JavaScript to view the <a href="http://disqus.com/?ref_noscript">comments powered by Disqus.</a></noscript> -<a href="http://disqus.com" class="dsq-brlink">comments powered by <span class="logo-disqus">Disqus</span></a> -</div> - - - - <div id="footer"> - <p> - - The Codex — - - Powered by <a href="http://markdoc.org/">Markdoc</a>. - -<a href="https://bitbucket.org/ojacobson/grimoire.ca/src/master/wiki/dev/debugger-101.md">See this page on Bitbucket</a> (<a href="https://bitbucket.org/ojacobson/grimoire.ca/history-node/master/wiki/dev/debugger-101.md">history</a>). - - </p> - </div> - -</div> -</body> -</html>
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