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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
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<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong Back Trace Information at O3"
href="https://bugs.llvm.org/show_bug.cgi?id=45883">45883</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong Back Trace Information at O3
</td>
</tr>
<tr>
<th>Product</th>
<td>clang
</td>
</tr>
<tr>
<th>Version</th>
<td>trunk
</td>
</tr>
<tr>
<th>Hardware</th>
<td>PC
</td>
</tr>
<tr>
<th>OS</th>
<td>Linux
</td>
</tr>
<tr>
<th>Status</th>
<td>NEW
</td>
</tr>
<tr>
<th>Keywords</th>
<td>wrong-debug
</td>
</tr>
<tr>
<th>Severity</th>
<td>normal
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>C
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedclangbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>massarelli@diag.uniroma1.it
</td>
</tr>
<tr>
<th>CC</th>
<td>blitzrakete@gmail.com, dgregor@apple.com, ditaliano@apple.com, erik.pilkington@gmail.com, llvm-bugs@lists.llvm.org, richard-llvm@metafoo.co.uk
</td>
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<p>
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<pre>Backtrace information seems wrong with O3 at line 17.
$ cat a.c
volatile int a, c;
int b;
void d() {
int *e = &b;
f:
*e ^= 10;
if (b)
goto f;
}
void g(int *h) {
if (!0 ^ b)
*h = 0;
}
int main() {
g(&b);
c;
a;
d();
}
$ clang -v
clang version 11.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
c25b20c0f6c13d68dbc2e185764082d61ae4a132)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation:
/usr/local/bin/../lib/gcc/x86_64-pc-linux-gnu/11.0.0
Selected GCC installation: /usr/local/bin/../lib/gcc/x86_64-pc-linux-gnu/11.0.0
Candidate multilib: .;@m64
Selected multilib: .;@m64
$ lldb -v
lldb version 11.0.0
clang revision c25b20c0f6c13d68dbc2e185764082d61ae4a132
llvm revision c25b20c0f6c13d68dbc2e185764082d61ae4a132
$ clang -O3 -g -o opt a.c
$ lldb opt
(lldb) target create "opt"
Current executable set to 'opt' (x86_64).
(lldb) b -l 17
Breakpoint 1: where = opt`main + 32 at a.c:17:3, address = 0x00000000004004d0
(lldb) r
Process 172 launched: 'opt' (x86_64)
Process 172 stopped
* thread #1, name = 'opt', stop reason = breakpoint 1.1
frame #0: 0x00000000004004d0 opt`main at a.c:17:3
14 int main() {
15 g(&b);
16 c;
-> 17 a;
18 d();
19 }
(lldb) bt
* thread #1, name = 'opt', stop reason = breakpoint 1.1
* frame #0: 0x00000000004004d0 opt`main at a.c:17:3
frame #1: 0x00007ffff7a05b97 libc.so.6`__libc_start_main + 231
frame #2: 0x00000000004003ba opt`_start + 42
(lldb) s
Process 172 stopped
* thread #1, name = 'opt', stop reason = step in
frame #0: 0x00000000004004d6 opt`main [inlined] d at a.c:17:3
14 int main() {
15 g(&b);
16 c;
-> 17 a;
18 d();
19 }
(lldb) bt
* thread #1, name = 'opt', stop reason = step in
* frame #0: 0x00000000004004d6 opt`main [inlined] d at a.c:17:3
frame #1: 0x00000000004004d6 opt`main at a.c:18
frame #2: 0x00007ffff7a05b97 libc.so.6`__libc_start_main + 231
frame #3: 0x00000000004003ba opt`_start + 42
(lldb)</pre>
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