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inconsistent behaviors: the source code lines an address belongs to is inconsistent at source-level debugging and instruction-level debugging #47436

Open Quuxplusone opened 3 years ago

Quuxplusone commented 3 years ago
Bugzilla Link PR48467
Status NEW
Importance P normal
Reported by Yibiao Yang (yangyibiao@nju.edu.cn)
Reported on 2020-12-09 23:38:53 -0800
Last modified on 2020-12-10 12:40:47 -0800
Version unspecified
Hardware PC Linux
CC dblaikie@gmail.com, jdevlieghere@apple.com, llvm-bugs@lists.llvm.org
Fixed by commit(s)
Attachments a.out (10112 bytes, application/x-executable)
Blocks
Blocked by
See also 
Created attachment 24259
binary

$ clang -v
Ubuntu clang version 12.0.0-++20201202063839+f0193623297-
1~exp1~20201202174527.2077
Target: x86_64-pc-linux-gnu
Thread model: posix
InstalledDir: /usr/bin
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/7.5.0
Found candidate GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/8
Found candidate GCC installation: /usr/lib/gcc/x86_64-linux-gnu/10
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
Selected GCC installation: /usr/bin/../lib/gcc/x86_64-linux-gnu/10
Candidate multilib: .;@m64
Selected multilib: .;@m64

$ lldb -v
lldb version 12.0.0

$ cat small.c
/* { dg-options "-O2" } */
/* { dg-do run } */

static const long long int TagTypeNumber = 0xffff000000000000ll;

long long int x;

void foo(void)
{
  x = TagTypeNumber + 1;    // Line 10
}

int main(int argc, char **argv)
{
  if (argc > 0)
    foo ();    // Line 16

  if ((x & TagTypeNumber) == TagTypeNumber)
  {
    unsigned y = (unsigned)x;
    __builtin_printf ("v: %u\n", y);
    if (y != 1)
      __builtin_abort ();
  }

  return 0;
}

$ clang -O2 -g small.c

$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/root/DeVIL/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main + 11 at small.c:15:12, address =
0x000000000040056b
(lldb) r
Process 42468 stopped
    frame #0: 0x000000000040056b a.out`main(argc=1, argv=0x00007fffffffe038) at small.c:15:12
-> 15     if (argc > 0)
(lldb) s
Process 42468 stopped
    frame #0: 0x000000000040056f a.out`main(argc=1, argv=0x00007fffffffe038) at small.c:16
-> 16       foo ();    // Line 16
(lldb) s
    frame #0: 0x000000000040056f a.out`main [inlined] foo at small.c:10:5
-> 10     x = TagTypeNumber + 1;    // Line 10
(lldb)

############################################################
We can found that when step line by line, 0x000000000040056f belongs to Line 16
and Line 10.
However, when step instruction by instruction, 0x000000000040056f only belongs
to Line 16 as follows:
############################################################

$ lldb a.out
(lldb) target create "a.out"
Current executable set to '/root/DeVIL/a.out' (x86_64).
(lldb) b main
Breakpoint 1: where = a.out`main + 11 at small.c:15:12, address =
0x000000000040056b
(lldb) r
Process 42608 stopped
    frame #0: 0x000000000040056b a.out`main(argc=1, argv=0x00007fffffffe038) at small.c:15:12
-> 15     if (argc > 0)
(lldb) si
Process 42608 stopped
    frame #0: 0x000000000040056d a.out`main(argc=1, argv=0x00007fffffffe038) at small.c:15:7
-> 15     if (argc > 0)
(lldb) si
Process 42608 stopped
    frame #0: 0x000000000040056f a.out`main(argc=1, argv=0x00007fffffffe038) at small.c:16
-> 16       foo ();    // Line 16
(lldb) si
Process 42608 stopped
    frame #0: 0x0000000000400573 a.out`main [inlined] foo at small.c:10:5
-> 10     x = TagTypeNumber + 1;    // Line 10
(lldb)
Quuxplusone commented 3 years ago

Attached a.out (10112 bytes, application/x-executable): binary