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<base href="https://bugs.llvm.org/">
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<body><table border="1" cellspacing="0" cellpadding="8">
<tr>
<th>Bug ID</th>
<td><a class="bz_bug_link
bz_status_NEW "
title="NEW - Wrong debug info generated at -O3 (-O0 is correct)"
href="https://bugs.llvm.org/show_bug.cgi?id=45153">45153</a>
</td>
</tr>
<tr>
<th>Summary</th>
<td>Wrong debug info generated at -O3 (-O0 is correct)
</td>
</tr>
<tr>
<th>Product</th>
<td>libraries
</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>Severity</th>
<td>enhancement
</td>
</tr>
<tr>
<th>Priority</th>
<td>P
</td>
</tr>
<tr>
<th>Component</th>
<td>DebugInfo
</td>
</tr>
<tr>
<th>Assignee</th>
<td>unassignedbugs@nondot.org
</td>
</tr>
<tr>
<th>Reporter</th>
<td>shuo.d@outlook.com
</td>
</tr>
<tr>
<th>CC</th>
<td>jdevlieghere@apple.com, keith.walker@arm.com, llvm-bugs@lists.llvm.org, paul_robinson@playstation.sony.com
</td>
</tr></table>
<p>
<div>
<pre>The expected output from lldb should be 20, but lldb outputs 0 when the program
is compiled with "-O3". It behaves correctly when the program is compiled with
"-O0".
In both cases, the debugger stops at line 7 and the tiny underscore is between
c and 0. I think this indicates that the debugger stops at the same breakpoint,
and in this case it should at least prints the same value. My understanding is
that the assignment operation of l_16 hasn't been executed, thus the correct
output should be 20.
$ cat abc.c
int a, b;
unsigned c;
int main() {
int l_16 = 0;
for (; l_16 < 20; l_16 = l_16 + 5)
;
l_16 = c = 0 // optimize_me_not0
^ a;
b = b & 1048575 ^ a;
}
$ cat cmds
b 7
r
p l_16
kill
q
$ clang-trunk -v
clang version 11.0.0 (<a href="https://github.com/llvm/llvm-project.git">https://github.com/llvm/llvm-project.git</a>
bdcbdb484829c518511eece0809cc8ce1baa73c8)
Target: x86_64-unknown-linux-gnu
Thread model: posix
InstalledDir: /usr/local/bin
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/i686-linux-gnu/9
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.4.7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.6.4
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/4.8.5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/5.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/6.5.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/7.4.0
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Selected GCC installation: /usr/lib/gcc/x86_64-linux-gnu/9
Candidate multilib: .;@m64
Candidate multilib: 32;@m32
Candidate multilib: x32;@mx32
Selected multilib: .;@m64
$ lldb-trunk -v
lldb version 11.0.0
clang revision bdcbdb484829c518511eece0809cc8ce1baa73c8
llvm revision bdcbdb484829c518511eece0809cc8ce1baa73c8
$ clang-trunk -g abc.c -O3
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/24200/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/24200/report/cmds'.
(lldb) b 7
Breakpoint 1: where = a.out`main + 17 at abc.c:7:12, address =
0x0000000000400491
(lldb) r
Process 5369 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x0000000000400491 a.out`main at abc.c:7:12
4 int l_16 = 0;
5 for (; l_16 < 20; l_16 = l_16 + 5)
6 ;
-> 7 l_16 = c = 0 // optimize_me_not0
8 ^ a;
9 b = b & 1048575 ^ a;
10 }
Process 5369 launched: '/home/sding/LLDB-testing/reduce/24200/report/a.out'
(x86_64)
(lldb) p l_16
(int) $0 = 0
(lldb) kill
Process 5369 exited with status = 9 (0x00000009)
(lldb) q
$ clang-trunk -g abc.c -O0
$ lldb-trunk -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/sding/LLDB-testing/reduce/24200/report/a.out'
(x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/sding/LLDB-testing/reduce/24200/report/cmds'.
(lldb) b 7
Breakpoint 1: where = a.out`main + 57 at abc.c:7:12, address =
0x00000000004004b9
(lldb) r
Process 6210 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
frame #0: 0x00000000004004b9 a.out`main at abc.c:7:12
4 int l_16 = 0;
5 for (; l_16 < 20; l_16 = l_16 + 5)
6 ;
-> 7 l_16 = c = 0 // optimize_me_not0
8 ^ a;
9 b = b & 1048575 ^ a;
10 }
Process 6210 launched: '/home/sding/LLDB-testing/reduce/24200/report/a.out'
(x86_64)
(lldb) p l_16
(int) $0 = 20
(lldb) kill
Process 6210 exited with status = 9 (0x00000009)
(lldb) q</pre>
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