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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 --- - False positive garbage value reported in std::<random> param_type in distribution templates"
href="http://llvm.org/bugs/show_bug.cgi?id=21344">21344</a>
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<th>Summary</th>
<td>False positive garbage value reported in std::<random> param_type in distribution templates
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>unspecified
</td>
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<th>Hardware</th>
<td>PC
</td>
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<th>OS</th>
<td>Linux
</td>
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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>Static Analyzer
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<th>Assignee</th>
<td>kremenek@apple.com
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<th>Reporter</th>
<td>stevemac321@live.com
</td>
</tr>
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<th>CC</th>
<td>llvmbugs@cs.uiuc.edu
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<th>Classification</th>
<td>Unclassified
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</tr></table>
<p>
<div>
<pre>To repro, navigate to
/libcxx/test/numerics/rand/rand.dis/rand.dist.bern/rand.dist.bern.bin
Run:
scan-build -k -analyze-headers clang++ -std=c++1y -stdlib=libc++ -g3 -O0
-I/home/comet/libcxx/include eval_param.pass.cpp
Result:
libcxx/include/random:4024:29: warning: The right operand of '-' is a garbage
value
double __u = __gen(__g) - __pr.__pr_;
^ ~~~~~~~~~~
The code looks like this:
template<class _IntType>
template<class _URNG>
_IntType
binomial_distribution<_IntType>::operator()(_URNG& __g, const param_type& __pr)
{
if (__pr.__t_ == 0 || __pr.__p_ == 0)
return 0;
if (__pr.__p_ == 1)
return __pr.__t_;
uniform_real_distribution<double> __gen;
double __u = __gen(__g) - __pr.__pr_; // warning on this line
However, I think it is fair to say that param_type will at least be a
default-constructed IntType. IntType is binomial_distribution's template
argument defaulted to int (class _IntType = int). param_type has to be
assignable to numeric types:
explicit param_type(result_type __t = 1, double __p = 0.5);
So, I don't know how a garbage value could compile, or how one would test for
garbage in binomial_distribution's call operator (warning location)</pre>
</div>
</p>
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