[lldb-dev] [Bug 45920] New: lldb wrongly stopped at a statement for nesting loop using step instruction

[via lldb-dev]

https://bugs.llvm.org/show_bug.cgi?id=45920

            Bug ID: 45920
           Summary: lldb wrongly stopped at a statement for nesting loop
                    using step instruction
           Product: lldb
           Version: unspecified
          Hardware: PC
                OS: Linux
            Status: NEW
          Severity: normal
          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

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

$ 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 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 + 11 at small.c:4:10, address =
0x000000000040111b
(lldb) r
Process 13529 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 13529 stopped
* thread #1, name = 'a.out', stop reason = breakpoint 1.1
    frame #0: 0x000000000040111b a.out`main at small.c:4:10
   1    int main ()
   2    {
   3      int x, y;
-> 4      for (x = __INT_MAX__ - 1; x < __INT_MAX__; x++)
   5        for (y = -1; y <= 0; y++)
   6          if ((x + 1 - y) != (int) (x + 1U - y))
   7            return 1;
(lldb) si -c 35
Process 13529 stopped
* thread #1, name = 'a.out', stop reason = instruction step into
    frame #0: 0x000000000040113a a.out`main at small.c:5:5
   2    {
   3      int x, y;
   4      for (x = __INT_MAX__ - 1; x < __INT_MAX__; x++)
-> 5        for (y = -1; y <= 0; y++)
   6          if ((x + 1 - y) != (int) (x + 1U - y))
   7            return 1;
   8      return 0;
(lldb) var
(int) x = 2147483646
(int) y = 1
(lldb) si
Process 13529 stopped
* thread #1, name = 'a.out', stop reason = instruction step into
    frame #0: 0x0000000000401179 a.out`main at small.c:7:16
   4      for (x = __INT_MAX__ - 1; x < __INT_MAX__; x++)
   5        for (y = -1; y <= 0; y++)
   6          if ((x + 1 - y) != (int) (x + 1U - y))
-> 7            return 1;
   8      return 0;
   9    }
(lldb) 



/******************************
lldb is wrongly stopped at Line 7.
However, when setting breakpoint at Line 7. The program is directly exit. 
*******************************/


$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/home/yibiao/Debugger/a.out' (x86_64).
(lldb) b 7
Breakpoint 1: where = a.out`main + 74 at small.c:7:9, address =
0x000000000040115a
(lldb) r
Process 13589 launched: '/home/yibiao/Debugger/a.out' (x86_64)
Process 13589 exited with status = 0 (0x00000000)



$ cat small.c
int main ()
{
  int x, y;
  for (x = __INT_MAX__ - 1; x < __INT_MAX__; x++)
    for (y = -1; y <= 0; y++)
      if ((x + 1 - y) != (int) (x + 1U - y))
        return 1;
  return 0;
}

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