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<base href="http://llvm.org/bugs/" />
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - -Wconditional-uninitialized false positive when usage is correctly constrained by other variable"
href="http://llvm.org/bugs/show_bug.cgi?id=17526">17526</a>
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<th>Summary</th>
<td>-Wconditional-uninitialized false positive when usage is correctly constrained by other variable
</td>
</tr>
<tr>
<th>Product</th>
<td>new-bugs
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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<th>Hardware</th>
<td>Macintosh
</td>
</tr>
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<th>OS</th>
<td>MacOS X
</td>
</tr>
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<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
</tr>
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<th>Component</th>
<td>new bugs
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
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<th>Reporter</th>
<td>sean@rogue-research.com
</td>
</tr>
<tr>
<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
</tr>
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider this C99:
-------------------------
#include <stdlib.h>
#include <stdio.h>
#include <stdbool.h>
typedef enum
{
kDog,
kCat,
} MyEnum;
int main (void)
{
bool isValid = false;
MyEnum animal; // NB: UNINITIALIZED!
int random = rand();
if (random == 420)
{
animal = kDog;
isValid = true;
}
if (isValid)
{
printf("animal is %u", animal);
}
return 0;
}
-------------------------
$ clang --version
clang version 3.4 (192323)
$ clang -Weverything -fsyntax-only ~/Desktop/test.c
/Users/sean/Desktop/test.c:25:26: warning: variable 'animal' may be
uninitialized when used here [-Wconditional-uninitialized]
printf("animal is %u", animal);
^~~~~~
/Users/sean/Desktop/test.c:14:2: note: variable 'animal' is declared here
MyEnum animal; // NB: UNINITIALIZED!
^
1 warning generated.
It's easy for a human to see that "animal" is only used if "isValid" is true
and that everywhere "isValid" is set to true, "animal" is also set to
something. The bug is that clang can't also see this. :)
This is a reduced test case of something similar but with many more if-else
branches.</pre>
</div>
</p>
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