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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - -fsanitize=undefined does not catch UB static pointers initialization"
href="https://bugs.llvm.org/show_bug.cgi?id=35782">35782</a>
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<th>Summary</th>
<td>-fsanitize=undefined does not catch UB static pointers initialization
</td>
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<th>Product</th>
<td>clang
</td>
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<th>Version</th>
<td>5.0
</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>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
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<th>Reporter</th>
<td>shachar@shemesh.biz
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<th>CC</th>
<td>dgregor@apple.com, llvm-bugs@lists.llvm.org
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<p>
<div>
<pre>Please consider the following (rather strange) program:
#include <cstdlib>
// _static_, no-one outside this translation unit can touch it
// Global static --> initialized to nullptr
static void (*fun) ();
void evil() {
system("rm -rf /");
}
void set() {
fun = &evil;
}
int main() {
fun(); // nullptr dereference = UB.
// Static variable, so no-one can touch it except us. So...
// the only non-UB thing that could have happened is that
// set() was called before main(). So let's assume that and
// continue optimization...
// >:D
}
When you switch the system call with a printf and compile with clang++-5.0, the
function gets triggered (-O3 -Wall -Wextra). The comment does a good job of
explaining why.
But when you add -fsanitize=undefined, I expected there to be some complaint
about the code running undefined behavior. No such complaint arises, and the
code still runs, still executes "evil", same as without the sanitizer.</pre>
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