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[zlaski/bad-addition-qhelp-reword] Left-justify help text so that it renders proerly in MD.

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Ziemowit Laski
2019-10-22 14:00:02 -07:00
parent ad4cd6f2bb
commit ac7a1230e6
1 changed files with 35 additions and 34 deletions
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69
cpp/ql/src/Likely Bugs/Arithmetic/BadAdditionOverflowCheck.qhelp
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@@ -2,38 +2,39 @@
"-//Semmle//qhelp//EN"
"qhelp.dtd">
<qhelp>
<overview>
<p>
Checking for overflow of integer addition needs to be done with
care, because automatic type promotion can prevent the check
from working as intended, with the same value (<code>true</code>
or <code>false</code>) always being returned.
</p>
</overview>
<recommendation>
<p>
Use an explicit cast to make sure that the result of the addition is
not implicitly converted to a larger type.
</p>
</recommendation>
<example>
<sample src="BadAdditionOverflowCheckExample1.cpp" />
<p>
On a typical architecture where <code>short</code> is 16 bits
and <code>int</code> is 32 bits, the operands of the addition are
automatically promoted to <code>int</code>, so it cannot overflow
and the result of the comparison is always false.
</p>
<p>
The code below implements the check correctly, by using an
explicit cast to make sure that the result of the addition
is <code>unsigned short</code> (which may overflow, in which case
the comparison would evaluate to <code>true</code>).
</p>
<sample src="BadAdditionOverflowCheckExample2.cpp" />
</example>
<references>
<li><a href="http://c-faq.com/expr/preservingrules.html">Preserving Rules</a></li>
<li><a href="https://www.securecoding.cert.org/confluence/plugins/servlet/mobile#content/view/20086942">Understand integer conversion rules</a></li>
</references>
<overview>
<p>
Checking for overflow of integer addition needs to be done with
care, because automatic type promotion can prevent the check
from working as intended, with the same value (<code>true</code>
or <code>false</code>) always being returned.
</p>
</overview>
<recommendation>
<p>
Use an explicit cast to make sure that the result of the addition is
not implicitly converted to a larger type.
</p>
</recommendation>
<example>
<sample src="BadAdditionOverflowCheckExample1.cpp" />
<p>
On a typical architecture where <code>short</code> is 16 bits
and <code>int</code> is 32 bits, the operands of the addition are
automatically promoted to <code>int</code>, so it cannot overflow
and the result of the comparison is always false.
</p>
<p>
The code below implements the check correctly, by using an
explicit cast to make sure that the result of the addition
is <code>unsigned short</code> (which may overflow, in which case
the comparison would evaluate to <code>true</code>).
</p>
<sample src="BadAdditionOverflowCheckExample2.cpp" />
</example>
<references>
<li><a href="http://c-faq.com/expr/preservingrules.html">Preserving Rules</a></li>
<li><a href="https://www.securecoding.cert.org/confluence/plugins/servlet/mobile#content/view/20086942">Understand integer conversion rules</a></li>
</references>
</qhelp>