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| 22 | <title>Postincrement and Ordering (GNU C Language Manual)</title>
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| 57 | <body lang="en">
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| 58 | <span id="Postincrement-and-Ordering"></span><div class="header">
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| 59 | <p>
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| 60 | Next: <a href="Ordering-of-Operands.html" accesskey="n" rel="next">Ordering of Operands</a>, Previous: <a href="Sequence-Points.html" accesskey="p" rel="prev">Sequence Points</a>, Up: <a href="Order-of-Execution.html" accesskey="u" rel="up">Order of Execution</a> [<a href="index.html#SEC_Contents" title="Table of contents" rel="contents">Contents</a>][<a href="Symbol-Index.html" title="Index" rel="index">Index</a>]</p>
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| 61 | </div>
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| 62 | <hr>
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| 63 | <span id="Postincrement-and-Ordering-1"></span><h3 class="section">10.4 Postincrement and Ordering</h3>
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| 64 | <span id="index-postincrement-and-ordering"></span>
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| 65 | <span id="index-ordering-and-postincrement"></span>
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| 66 |
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| 67 | <p>Ordering requirements are loose with the postincrement and
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| 68 | postdecrement operations (see <a href="Postincrement_002fPostdecrement.html">Postincrement/Postdecrement</a>), which
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| 69 | specify side effects to happen “a little later.” They must happen
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| 70 | before the next sequence point, but that still leaves room for various
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| 71 | meanings. In this expression,
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| 72 | </p>
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| 73 | <div class="example">
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| 74 | <pre class="example">z = x++ - foo ()
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| 75 | </pre></div>
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| 76 |
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| 77 | <p>it’s unpredictable whether <code>x</code> gets incremented before or after
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| 78 | calling the function <code>foo</code>. If <code>foo</code> refers to <code>x</code>,
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| 79 | it might see the old value or it might see the incremented value.
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| 80 | </p>
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| 81 | <p>In this perverse expression,
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| 82 | </p>
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| 83 | <div class="example">
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| 84 | <pre class="example">x = x++
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| 85 | </pre></div>
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| 86 |
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| 87 | <p><code>x</code> will certainly be incremented but the incremented value may
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| 88 | not stick. If the incrementation of <code>x</code> happens after the
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| 89 | assignment to <code>x</code>, the incremented value will remain in place.
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| 90 | But if the incrementation happens first, the assignment will overwrite
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| 91 | that with the not-yet-incremented value, so the expression as a whole
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| 92 | will leave <code>x</code> unchanged.
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| 93 | </p>
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| 94 |
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| 95 |
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| 96 |
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| 97 | </body>
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| 98 | </html>
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