[Bug symtab/26059] New: inconsistent behaviors at -O0

[Bug symtab/26059] New: inconsistent behaviors at -O0

[yangyibiao at hust dot edu.cn]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

            Bug ID: 26059
           Summary: inconsistent behaviors at -O0
           Product: gdb
           Version: HEAD
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: symtab
          Assignee: unassigned at sourceware dot org
          Reporter: yangyibiao at hust dot edu.cn
  Target Milestone: ---

Created attachment 12575
  --> https://sourceware.org/bugzilla/attachment.cgi?id=12575&action=edit
a.out

$ gcc --version
gcc (GCC) 10.0.1 20200419 (experimental)
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

$ gdb --version
GNU gdb (GDB) 10.0.50.20200517-git
Copyright (C) 2020 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.


$ cat small.c
unsigned int b,d;
static int c[1][2] = {{0, 1}};

int main() {
  for (; d<1; d++)
    for (; b<1; b++)
      c[b][d+1] = 0;

  return 0;
}

/*****************************************************
When stepping using stepi, gdb first hit Line 6 and then hit Line 7 with stepi
for the first iteration of the second for loop.
******************************************************/

$ gcc -O0 -g small.c

$ gdb -q a.out
Reading symbols from a.out...
(gdb) b 5
Breakpoint 1 at 0x401106: file small.c, line 5.
(gdb) r
Starting program: /home/yibiao/Debugger/a.out 

Breakpoint 1, main () at small.c:5
5         for (; d<1; d++)
(gdb) stepi
0x0000000000401154      5         for (; d<1; d++)
(gdb) stepi
0x000000000040115a      5         for (; d<1; d++)
(gdb) stepi
0x000000000040115c      5         for (; d<1; d++)
(gdb) stepi
0x000000000040113b      6           for (; b<1; b++)
(gdb) stepi
0x0000000000401141      6           for (; b<1; b++)
(gdb) stepi
0x0000000000401143      6           for (; b<1; b++)
(gdb) stepi
7             c[b][d+1] = 0;
(gdb)


/*****************************************************
When stepping with step, gdb is first hit Line 7 and then hit Line 6.
This is an inconsistent behaviors between stepi and step.
*****************************************************/


$ gdb -q a.out
Reading symbols from a.out...
(gdb) b main
Breakpoint 1 at 0x401106: file small.c, line 5.
(gdb) r
Starting program: /home/yibiao/Debugger/a.out 

Breakpoint 1, main () at small.c:5
5         for (; d<1; d++)
(gdb) step
7             c[b][d+1] = 0;
(gdb) 
6           for (; b<1; b++)
(gdb) 


Breakpoint 1, main () at small.c:6
6           for (; b<1; b++)
(gdb)


Note that, I submit this bug to gcc
(https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95360) and Tom de Vries commented
that this bug should belongs to gdb.

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[Bug symtab/26059] inconsistent Inconsistent order of execution at -O0

[yangyibiao at hust dot edu.cn]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

Yibiao Yang <yangyibiao at hust dot edu.cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|inconsistent behaviors at   |inconsistent Inconsistent
                   |-O0                         |order of execution at -O0

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[Bug symtab/26059] Inconsistent order of execution at -O0

[yangyibiao at hust dot edu.cn]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

Yibiao Yang <yangyibiao at hust dot edu.cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|inconsistent Inconsistent   |Inconsistent order of
                   |order of execution at -O0   |execution at -O0

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[Bug symtab/26059] Inconsistent order of execution at -O0

[yangyibiao at hust dot edu.cn]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

Yibiao Yang <yangyibiao at hust dot edu.cn> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |rguenth at gcc dot gnu.org

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[Bug symtab/26059] Inconsistent order of execution at -O0

[yangyibiao at outlook dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

Yibiao Yang <yangyibiao at outlook dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
                 CC|                            |vries at gcc dot gnu.org

--- Comment #1 from Yibiao Yang <yangyibiao at outlook dot com> ---
I can produced it in the current version of GDB.

$ gcc --version; gdb --version
gcc (Ubuntu 10.2.0-5ubuntu1~20.04) 10.2.0
Copyright (C) 2020 Free Software Foundation, Inc.
This is free software; see the source for copying conditions.  There is NO
warranty; not even for MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.

GNU gdb (GDB) 11.0.50.20210113-git
Copyright (C) 2021 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.

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[Bug symtab/26059] Inconsistent order of execution at -O0

[vries at gcc dot gnu.org]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

--- Comment #2 from Tom de Vries <vries at gcc dot gnu.org> ---
(In reply to Yibiao Yang from comment #0)
> Note that, I submit this bug to gcc
> (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95360) and Tom de Vries
> commented that this bug should belongs to gdb.

Is this not a duplicate of PR26054 ?

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[Bug symtab/26059] Inconsistent order of execution at -O0

[yangyibiao at outlook dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

--- Comment #3 from Yibiao Yang <yangyibiao at outlook dot com> ---
(In reply to Tom de Vries from comment #2)
> (In reply to Yibiao Yang from comment #0)
> > Note that, I submit this bug to gcc
> > (https://gcc.gnu.org/bugzilla/show_bug.cgi?id=95360) and Tom de Vries
> > commented that this bug should belongs to gdb.
> 
> Is this not a duplicate of PR26054 ?

I am very sorry. Yes, it is indeed a duplicate of PR26054. 
since LLDB behaves as expected, I reported it as a gdb bug as well.

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[Bug symtab/26059] Inconsistent order of execution at -O0

[yangyibiao at outlook dot com]

https://sourceware.org/bugzilla/show_bug.cgi?id=26059

Yibiao Yang <yangyibiao at outlook dot com> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Status|UNCONFIRMED                 |RESOLVED
         Resolution|---                         |DUPLICATE

--- Comment #4 from Yibiao Yang <yangyibiao at outlook dot com> ---
Duplicate of 26054

*** This bug has been marked as a duplicate of bug 26054 ***

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