<!DOCTYPE qhelp PUBLIC

"-//Semmle//qhelp//EN"

"qhelp.dtd">

<qhelp>

<overview>

<p>When a function call returns two values, a pointer and a (subtype of) error, it is conventional to assume that the pointer

might be nil until either the pointer or error value has been checked.</p>

<p>If the pointer is dereferenced without a check, an unexpected nil pointer dereference panic may occur.</p>

</overview>

<recommendation>

<p>Ensure that the returned pointer is either directly checked against nil, or the error value is checked before using

the returned pointer.</p>

</recommendation>

<example>

<p>In the example below, <code>user</code> dereferences <code>ptr</code> without checking either

<code>ptr</code> or <code>err</code>. This might lead to a panic.</p>

<sample src="MissingErrorCheck.go" />

<p>The corrected version of <code>user</code> checks <code>err</code> before using <code>ptr</code>.</p>

<sample src="MissingErrorCheckGood.go" />

</example>

<references>

<li>

The Go Blog:

<a href="https://blog.golang.org/error-handling-and-go">Error handling and Go</a>.

</li>

</references>

</qhelp>