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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - sanitize float-cast-overflow false positive with 255.5 to uint8_t?"
href="http://llvm.org/bugs/show_bug.cgi?id=15383">15383</a>
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<th>Summary</th>
<td>sanitize float-cast-overflow false positive with 255.5 to uint8_t?
</td>
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<th>Product</th>
<td>new-bugs
</td>
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<th>Version</th>
<td>trunk
</td>
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<th>Hardware</th>
<td>Macintosh
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<th>OS</th>
<td>MacOS X
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<th>Status</th>
<td>NEW
</td>
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<th>Severity</th>
<td>normal
</td>
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<th>Priority</th>
<td>P
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<th>Component</th>
<td>new bugs
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<th>Assignee</th>
<td>unassignedbugs@nondot.org
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<th>Reporter</th>
<td>sean@rogue-research.com
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
</td>
</tr></table>
<p>
<div>
<pre>Consider this C++:
-------------------
#include <stdint.h>
int main (void)
{
double d = 255.5;
uint8_t c = (uint8_t)d;
return c;
}
-------------------
then:
$ clang++ -fsanitize=float-cast-overflow test.cxx
runtime error: value 255.5 is outside the range of representable values of type
'unsigned char'
The standard seems to say "An rvalue of a floating point type can be converted
to an rvalue of an integer type. The conversion truncates; that is, the
fractional part is discarded. The behavior is undefined if the ***truncated***
value cannot be represented in the destination type." (emphasis mine)
So I believe clang is wrong to warn here.</pre>
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