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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - Comparison against functions is almost always erroneous, should warn"
href="http://llvm.org/bugs/show_bug.cgi?id=17900">17900</a>
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<th>Summary</th>
<td>Comparison against functions is almost always erroneous, should warn
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>All
</td>
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>enhancement
</td>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>Frontend
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>oneill+llvmbugs@cs.hmc.edu
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
</td>
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<th>Classification</th>
<td>Unclassified
</td>
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<p>
<div>
<pre>Consider this code:
#include <strings.h>
int indx;
int isIndxZero()
{
return index == 0;
}
Here the user has mistakenly written “indx” as “index“, which happens to be a
POSIX.1 function. In this comparison, index decays to a pointer-to-function,
is then compared to zero, which becomes interpreted as the null pointer
constant.
As the address of a callable function, index would *never* be null, so at the
very least, this is a comparison that is likely always false.
It would be nice if at the very least we could warn that the comparison is
false, or better yet, warn about comparing a function with an integer.
Also, if as a result we ended up warning for &indx == 0, that'd be great too,
since that too is always false.</pre>
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</p>
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