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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW --- - False positive warning: Use of memory after it is freed (use of pointer, not memory)"
href="http://llvm.org/bugs/show_bug.cgi?id=16499">16499</a>
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<th>Summary</th>
<td>False positive warning: Use of memory after it is freed (use of pointer, not memory)
</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>MacOS X
</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
</td>
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<th>Component</th>
<td>Static Analyzer
</td>
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<th>Assignee</th>
<td>kremenek@apple.com
</td>
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<th>Reporter</th>
<td>ruslan_baratov@yahoo.com
</td>
</tr>
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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>Clang static analyzer give false warning that memory used after it is freed.
Warning is bogus because only pointer value is used, but not memory it points
to.
Example:
<span class="quote">>cat test.cpp </span >
#include <iostream> // std::cout
#include <stdlib.h> // malloc
void f() {
char *buffer = (char *)malloc(10);
free(buffer);
std::cout << (void *)buffer << std::endl;
// OK, memory freed, but only pointer value needed
}
<span class="quote">>clang++ --analyze test.cpp </span >
test.cpp:7:3: warning: Use of memory after it is freed
std::cout << (void *)buffer << std::endl;
^ ~~~~~~~~~~~~~~
1 warning generated.
This is simplified version of warning that can be found in libc++ sources
libcxx/src/debug.cpp, '__libcpp_db::__erase_i' method.
Environment:
<span class="quote">>clang++ --version</span >
Apple LLVM version 4.2 (clang-425.0.28) (based on LLVM 3.2svn)
Target: x86_64-apple-darwin11.4.2
Thread model: posix
<span class="quote">>uname -a</span >
Darwin mac-osx-x64 11.4.2 Darwin Kernel Version 11.4.2 ...</pre>
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