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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - clang-analyzer-security.FloatLoopCounter is too aggressive"
href="https://bugs.llvm.org/show_bug.cgi?id=38523">38523</a>
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<th>Summary</th>
<td>clang-analyzer-security.FloatLoopCounter is too aggressive
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
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<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>PC
</td>
</tr>
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<th>OS</th>
<td>All
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
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<th>Severity</th>
<td>enhancement
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>Static Analyzer
</td>
</tr>
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<th>Assignee</th>
<td>dcoughlin@apple.com
</td>
</tr>
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<th>Reporter</th>
<td>ldalessandro@gmail.com
</td>
</tr>
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<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>The documentation references CERT: FLP30-C, FLP30-CPP as the basis for this
check.
From
<a href="https://wiki.sei.cmu.edu/confluence/display/c/FLP30-C.+Do+not+use+floating-point+variables+as+loop+counters">https://wiki.sei.cmu.edu/confluence/display/c/FLP30-C.+Do+not+use+floating-point+variables+as+loop+counters</a>,
<span class="quote">> For the purpose of this rule, a loop counter is an induction variable
> that is used as an operand of a comparison expression that is used as
> the controlling expression of a do, while, or for loop. An induction
> variable is a variable that gets increased or decreased by a fixed
> amount on every iteration of a loop [Aho 1986]. Furthermore, the change
> to the variable must occur directly in the loop body (rather than
> inside a function executed within the loop).</span >
The implementation of this check incorrectly flags the following for loop as
failing.
<span class="quote">> for (double t = 0.0, dt = 0.0; t < 1.0; t += dt) {
> dt = f();
> }</span >
In this case, t is not an induction variable and should not be flagged, as dt
is not fixed. This is a common looping structure in numerical methods.
See the last comment (David Svoboda at the time of writing) at
<a href="https://wiki.sei.cmu.edu/confluence/display/java/NUM09-J.+Do+not+use+floating-point+variables+as+loop+counters">https://wiki.sei.cmu.edu/confluence/display/java/NUM09-J.+Do+not+use+floating-point+variables+as+loop+counters</a>
for reference.</pre>
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