[llvm-bugs] [Bug 46006] New: Wrong debug info generated at -O3 (-O0 is correct)

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46006

            Bug ID: 46006
           Summary: Wrong debug info generated at -O3 (-O0 is correct)
           Product: libraries
           Version: trunk
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          Priority: P
         Component: DebugInfo
          Assignee: unassignedbugs at nondot.org
          Reporter: yangyibiao at hust.edu.cn
                CC: jdevlieghere at apple.com, keith.walker at arm.com,
                    llvm-bugs at lists.llvm.org,
                    paul_robinson at playstation.sony.com

lldb outputs 0 when the program is compiled with "-O3". It behaves correctly
when the program is compiled with "-O0".

$ cat small.c
void foo(int *a) {
  (*a)++;
}

int main() {
  int a = 0;
  foo (&a);
  return 0;
}

$ cat cmds
b 8
r
p a


$ clang --version
clang version 11.0.0 (/home/yibiao/.cache/yay/llvm-git/llvm-project
871beba234a83a2a02da9dedbd59b91a1bfbd7af)
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin

$ lldb --version
lldb version 11.0.0
  clang revision 871beba234a83a2a02da9dedbd59b91a1bfbd7af
  llvm revision 871beba234a83a2a02da9dedbd59b91a1bfbd7af


$ clang -g -O0 small.c
$ lldb -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/yibiao/Debugger/cmds'.
(lldb) b 8
Breakpoint 1: where = a.out`main + 33 at small.c:8:3, address =
0x0000000000401151
(lldb) r
Process 3458 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x0000000000401151 a.out`main at small.c:8:3
   5    int main() {
   6      int a = 0;
   7      foo (&a);
-> 8      return 0;
   9    }

Process 3458 launched: '/home/yibiao/Debugger/a.out' (x86_64)
(lldb) p a
(int) $0 = 1


$ clang -g -O3 small.c
$ lldb -s cmds -b a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) command source -s 0 'cmds'
Executing commands in '/home/yibiao/Debugger/cmds'.
(lldb) b 8
Breakpoint 1: where = a.out`main at small.c:8:3, address = 0x0000000000401120
(lldb) r
Process 3563 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x0000000000401120 a.out`main at small.c:8:3
   5    int main() {
   6      int a = 0;
   7      foo (&a);
-> 8      return 0;
   9    }

Process 3563 launched: '/home/yibiao/Debugger/a.out' (x86_64)
(lldb) p a
(int) $0 = 0

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