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<base href="https://bugs.llvm.org/">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Signed integer overflow causes program to skip the epilogue and fall into another function"
href="https://bugs.llvm.org/show_bug.cgi?id=49599">49599</a>
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<th>Summary</th>
<td>Signed integer overflow causes program to skip the epilogue and fall into another function
</td>
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<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
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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>
</tr>
<tr>
<th>Severity</th>
<td>release blocker
</td>
</tr>
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<th>Priority</th>
<td>P
</td>
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<th>Component</th>
<td>C++
</td>
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<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>m13253@hotmail.com
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
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<p>
<div>
<pre>Comment:
Clang 13 simply does not generate any code for f1 after the undefined behavior
point. So any call onto f1 will eventually ends up fell into f2.
Although the compiler can do anything with an undefined behavior, including
simply crashing, infinite loop, playing some music, or nuke the earth without
violating the C++ specification. I still hope this undefined behavior won't be
that surprising.
This issue is not observed in C frontend, or Clang 12.
Godbolt link for your convenience: <a href="https://godbolt.org/z/r3nWrE">https://godbolt.org/z/r3nWrE</a>
Source code:
#include <stdio.h>
void f1(void) {
for(int i = 0; i >= 0; i++) {
// Undefined behavior
}
}
void f2(void) {
puts("Formatting /dev/sda1...");
// system("mkfs -t btrfs -f /dev/sda1");
}
// Prevents inlining
void (*volatile p1)(void) = f1;
void (*volatile p2)(void) = f2;
int main(void) {
puts(__VERSION__);
p1();
return 0;
}
Output:
Clang 13.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
fcdf7f6224610a51dc2ff47f2f1e3377329b64a7)
Formatting /dev/sda1...</pre>
</div>
</p>
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