Author: zaks
Date: Mon Jun 11 17:09:44 2012
New Revision: 158331
URL: http://llvm.org/viewvc/llvm-project?rev=158331&view=rev
Log:
[analyzer] WWW: Add table of contents, fixed code examples.
Modified:
cfe/trunk/www/analyzer/faq.html
Modified: cfe/trunk/www/analyzer/faq.html
URL:
http://llvm.org/viewvc/llvm-project/cfe/trunk/www/analyzer/faq.html?rev=158331&r1=158330&r2=158331&view=diff
==============================================================================
--- cfe/trunk/www/analyzer/faq.html (original)
+++ cfe/trunk/www/analyzer/faq.html Mon Jun 11 17:09:44 2012
@@ -19,15 +19,36 @@
<h1>FAQ and How to Deal with Common False Positives</h1>
-<h4 class="faq">Q: How do I tell the analyzer that I do not want the bug being
+<ol>
+ <li><a href="#custom_assert">How do I tell the analyzer that I do not want
the bug being
+reported here since my custom error handler will safely end the execution
before
+the bug is reached?</a></li>
+ <li><a href="#null_pointer">The analyzer reports a null dereference, but I
know that the
+pointer is never null. How can I tell the analyzer that a pointer can never be
+null?</a></li>
+ <li><a href="#use_assert">The analyzer assumes that a loop body is never
entered. How can I tell it that the loop body will be entered at least
once?</a></li>
+ <li><a href="#suppress_issue">How can I suppress a specific analyzer
warning?</a></li>
+</ol>
+
+
+<h4 id="custom_assert" class="faq">Q: How do I tell the analyzer that I do not
want the bug being
reported here since my custom error handler will safely end the execution
before
the bug is reached?</h4>
<img src="images/example_custom_assert.png" alt="example custom assert">
-<p>You can tell the analyzer that this path is unreachable by teaching it
about your <a href = "annotations.html#custom_assertions" >custom assertion
handlers</a>.</p>
+<p>You can tell the analyzer that this path is unreachable by teaching it
about your <a href = "annotations.html#custom_assertions" >custom assertion
handlers</a>. For example, you can modify the code segment as following.</p>
-<h4 class="faq">Q: The analyzer reports a null dereference, but I know that the
+<pre class="code_example">
+void customAssert() <span
class="code_highlight">__attribute__((analyzer_noreturn))</span>;
+int foo(int *b) {
+ if (!b)
+ customAssert();
+ return *b;
+}</pre>
+
+
+<h4 id="null_pointer" class="faq">Q: The analyzer reports a null dereference,
but I know that the
pointer is never null. How can I tell the analyzer that a pointer can never be
null?</h4>
@@ -35,7 +56,14 @@
<p>The reason the analyzer often thinks that a pointer can be null is because
the preceding code checked compared it against null. So if you are absolutely
sure that it cannot be null, remove the preceding check and, preferably, add an
assertion as well. For example, in the code segment above, it will be
sufficient to remove the <tt>if (!b)</tt> check. </p>
-<h4 class="faq">Q: The analyzer assumes that a loop body is never entered.
How can I tell it that the loop body will be entered at least once?</h4>
+<pre class="code_example">
+void usePointer(int *b);
+int foo(int *b) {
+ usePointer(b);
+ return *b;
+}</pre>
+
+<h4 id="use_assert" class="faq">Q: The analyzer assumes that a loop body is
never entered. How can I tell it that the loop body will be entered at least
once?</h4>
<img src="images/example_use_assert.png" alt="example use assert">
@@ -47,9 +75,17 @@
suppressed by asserting this knowledge, adding <tt>assert(length > 0)</tt> in
the beginning of the function.</p>
-<h4 class="faq">Q: How can I suppress a specific analyzer warning?</h4>
+<pre class="code_example">
+int foo(int length) {
+ int x = 0;
+ <span class="code_highlight">assert(length > 0);</span>
+ for (int i = 0; i < length; i++)
+ x += 1;
+ return length/x;
+}
+</pre>
-<img src="images/example_null_pointer.png" alt="example null pointer">
+<h4 id="suppress_issue" class="faq">Q: How can I suppress a specific analyzer
warning?</h4>
<p>There is currently no mechanism for suppressing the analyzer warning,
although this is currently being investigated. If you encounter an analyzer
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