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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - False positives"
href="http://llvm.org/bugs/show_bug.cgi?id=15891">15891</a>
</td>
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<tr>
<th>Summary</th>
<td>False positives
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>unspecified
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
<tr>
<th>OS</th>
<td>MacOS X
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
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<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>kremenek@apple.com
</td>
</tr>
<tr>
<th>Reporter</th>
<td>avitzur@gmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
<tr>
<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>I'm not sure which version of clang is in Xcode 4.6.2. It generates two false
positives in the following:
#include <iostream>
int Test1(unsigned int x);
void Test2(int x, int y);
int main(int argc, const char * argv[])
{
Test2(0,100);
return Test1(51);
}
int Test1(unsigned int x)
{
int a;
switch (x & 0x3)
{
case 0: a = 1; break;
case 1: a = 2; break;
case 2: a = 3; break;
case 3: a = 4; break;
}
std::cout << "Test 1";
return a;
// False positive Undefined or garbage value returned to caller, but x&0x3 can
be only 0,1,2, or 3. Making case 3 default: eliminates the false positive.
}
void Test2(int x, int y)
{
int n = 10;
int a[100];
for (int i = 0; i < y; i++)
a[i] = 0;
for (int i = 0; i < 50; i++) {
int w = i;
if (w > a[x?0:(i / n)]) a[x?0:(i / n)] = w;
// The right operand of '>' is a garbage value
// moving the array index into a local or moving y into a local eliminates the
false positive.
}
std::cout << "Test 2\n";
}</pre>
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