GlobalUseBeforeInit.qhelp

<!DOCTYPE qhelp PUBLIC
  "-//Semmle//qhelp//EN"
  "qhelp.dtd">
<qhelp>


<overview>
<p>This rule finds calls to functions that use a global variable before the variable has been initialized. 
Not all compilers generate code that zero-out memory, especially when optimizations are enabled or the compiler 
is not compliant with the latest language standards. Accessing uninitialized memory will lead to undefined results.
</p>

<include src="dataFlowWarning.inc.qhelp" />
</overview>

<recommendation>
<p>
Initialize the global variable. If no constant can be used for initialization, ensure that all accesses to the variable occur after
the initialization code is executed.
</p>
</recommendation>
<example>
<p>
In the example below, <code>callCtr</code> is wrongly used before it has been initialized.
</p>
<sample src="GlobalUseBeforeInit.cpp" />
</example>

<references>
<li>SEI CERT C++ Coding Standard: <a href="https://wiki.sei.cmu.edu/confluence/display/cplusplus/EXP53-CPP.+Do+not+read+uninitialized+memory">EXP53-CPP. Do not read uninitialized memory</a>.</li>
</references>
</qhelp>