[llvm-bugs] [Bug 46049] New: inconsistent behaviors at -O2

[via llvm-bugs]

https://bugs.llvm.org/show_bug.cgi?id=46049

            Bug ID: 46049
           Summary: inconsistent behaviors at -O2
           Product: lldb
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: enhancement
          Priority: P
         Component: All Bugs
          Assignee: lldb-dev at lists.llvm.org
          Reporter: yangyibiao at hust.edu.cn
                CC: jdevlieghere at apple.com, llvm-bugs at lists.llvm.org

$ 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 -O2 small.c

$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) b 6
Breakpoint 1: where = a.out`main + 29 at small.c:6:7, address =
0x000000000040112d
(lldb) r
Process 578366 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 578366 exited with status = 0 (0x00000000) 
(lldb) 


/********************************
As showed above, Line 6 is not hit by lldb when setting breakpoint.
However, it was hit by lldb when using step-i
*********************************/


$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main at small.c:4:7, address = 0x0000000000401110
(lldb) r
Process 578410 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 578410 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x0000000000401110 a.out`main at small.c:4:7
   1    int a, b, d=1;
   2    
   3    int main() {
-> 4      if (d)
   5        a = b==0;
   6      if (a!=1)
   7        return 1;
(lldb) si -c 7
Process 578410 stopped
* thread #1, name = 'a.out', stop reason = instruction step into
    frame #0: 0x0000000000401133 a.out`main at small.c:6:8
   3    int main() {
   4      if (d)
   5        a = b==0;
-> 6      if (a!=1)
   7        return 1;
   8      return 0;
   9    }
(lldb) 




$ cat small.c
int a, b, d=1;

int main() {
  if (d)
    a = b==0;
  if (a!=1)
    return 1;
  return 0;
}

--- Comment #1 from Yibiao Yang (杨已彪) <yangyibiao at hust.edu.cn> ---
Created attachment 23536
  --> https://bugs.llvm.org/attachment.cgi?id=23536&action=edit
the binary

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