<html>
<head>
<base href="https://bugs.llvm.org/">
</head>
<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - false positive null pointer analysis due to not inlined list operator == and !="
href="https://bugs.llvm.org/show_bug.cgi?id=38199">38199</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>false positive null pointer analysis due to not inlined list operator == and !=
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>Static Analyzer
</td>
</tr>
<tr>
<th>Assignee</th>
<td>dcoughlin@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>chh@google.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvm-bugs@lists.llvm.org
</td>
</tr></table>
<p>
<div>
<pre>To reproduce:
$ cat /tmp/null.cpp
#include <list>
typedef std::list<int*> MyList;
extern MyList &mylist;
struct A {
A();
void f0();
};
extern void f1(), f2();
void foo()
{
A *p = nullptr;
MyList::iterator begin = mylist.begin();
MyList::iterator end = mylist.end();
if (begin != end) {
f1();
p = new A();
}
if (!(begin != end)) {
f2();
if (p != nullptr) delete p;
p = new A();
}
p->f0();
delete p;
}
$ clang-tidy -checks=-*,clang-analy* /tmp/null.cpp -- -std=c++11 -O2
/tmp/null.cpp:23:3: warning: Called C++ object pointer is null
[clang-analyzer-core.CallAndMessage]
p->f0();
^
/tmp/null.cpp:11:3: note: 'p' initialized to a null pointer value
A *p = nullptr;
^
/tmp/null.cpp:14:7: note: Assuming the condition is false
if (begin != end) {
^
/tmp/null.cpp:14:3: note: Taking false branch
if (begin != end) {
^
/tmp/null.cpp:18:7: note: Assuming the condition is false
if (!(begin != end)) {
^
/tmp/null.cpp:18:3: note: Taking false branch
if (!(begin != end)) {
^
/tmp/null.cpp:23:3: note: Called C++ object pointer is null
p->f0();
^
If compiled with clang -O2, we can see that all calls to the list and iterator
functions can be inlined and it is impossible to have both !(begin != end) and
!!(begin != end)
The clang static analyzer does not seem be inlining the != and == operators of
the list::iterator.</pre>
</div>
</p>
<hr>
<span>You are receiving this mail because:</span>
<ul>
<li>You are on the CC list for the bug.</li>
</ul>
</body>
</html>