[Bug debug/107154] New: GDB jumping to end of block when stepping over construction of local variable

[Bug debug/107154] New: GDB jumping to end of block when stepping over construction of local variable

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

            Bug ID: 107154
           Summary: GDB jumping to end of block when stepping over
                    construction of local variable
           Product: gcc
           Version: 12.2.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: debug
          Assignee: unassigned at gcc dot gnu.org
          Reporter: redi at gcc dot gnu.org
  Target Milestone: ---

#include <initializer_list>
#include <string>

struct X {
  X(std::initializer_list<std::string>, int) { }
};

int main()
{
  X x( {"", "", "", ""}, 1|4 );
  return 0;
}

tmp$ g++ -g debug.C -o debug
tmp$ gdb -q debug
Reading symbols from debug...
(gdb) start
Temporary breakpoint 1 at 0x40123a: file debug.C, line 12.
Starting program: /tmp/debug 
[Thread debugging using libthread_db enabled]
Using host libthread_db library "/lib64/libthread_db.so.1".

Temporary breakpoint 1, main () at debug.C:12
12      }
(gdb) n
10        X x( {"", "", "", ""}, 1|4 );
(gdb) 
12      }
(gdb) 
11        return 0;
(gdb) 
__libc_start_call_main (main=main@entry=0x401226 <main()>, argc=argc@entry=1,
argv=argv@entry=0x7fffffffd7a8) at ../sysdeps/nptl/libc_start_call_main.h:74
74        exit (result);
(gdb) 
[Inferior 1 (process 577012) exited normally]


Why does "start" break on the closing brace of main(), and then the
construction of 'x' also jumps to the closing brace?

In less trivial examples I've seen it jump back and forth multiple times:

243             libmap libs;
(gdb) n
245       redi::ipstream in({"ldd", argv[arg]}, pstdout|pstderr);
(gdb) 
310     }
(gdb) 
245       redi::ipstream in({"ldd", argv[arg]}, pstdout|pstderr);
(gdb) 
310     }
(gdb) 
245       redi::ipstream in({"ldd", argv[arg]}, pstdout|pstderr);
(gdb) 
[Detaching after fork from child process 845854]
310     }
(gdb)

[Bug debug/107154] GDB jumping to end of block when stepping over construction of local variable

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

--- Comment #1 from Jonathan Wakely <redi at gcc dot gnu.org> ---
This is with the Fedora packages but I see it with GCC trunk too.

$ rpm -q gcc gdb
gcc-12.2.1-2.fc36.x86_64
gdb-12.1-1.fc36.x86_64

[Bug debug/107154] GDB jumping to end of block when stepping over construction of local variable

[pinskia at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

--- Comment #2 from Andrew Pinski <pinskia at gcc dot gnu.org> ---
I think there is another bug about this one ...

[Bug debug/107154] [12/13 Regression] GDB jumping to end of block when stepping over construction of local variable

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Last reconfirmed|                            |2022-10-04
     Ever confirmed|0                           |1
             Status|UNCONFIRMED                 |ASSIGNED
           Assignee|unassigned at gcc dot gnu.org      |jason at gcc dot gnu.org
                 CC|                            |jason at gcc dot gnu.org

[Bug debug/107154] [12/13 Regression] GDB jumping to end of block when stepping over construction of local variable

[redi at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

--- Comment #3 from Jonathan Wakely <redi at gcc dot gnu.org> ---
It started with r12-6329

 c++: EH and partially constructed aggr temp [PR66139]

[Bug debug/107154] [12/13 Regression] GDB jumping to end of block when stepping over construction of local variable

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

--- Comment #4 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The master branch has been updated by Jason Merrill <jason@gcc.gnu.org>:

https://gcc.gnu.org/g:ce3a1b5976079b1467473b4628f05797fd2eae08

commit r13-3072-gce3a1b5976079b1467473b4628f05797fd2eae08
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Oct 4 17:06:04 2022 -0400

    c++: fix debug info for array temporary [PR107154]

    In the testcase the elaboration of the array init that happens at
genericize
    time was getting the location info for the end of the function; fixed by
    doing the expansion at the location of the original expression.

            PR c++/107154

    gcc/cp/ChangeLog:

            * cp-gimplify.cc (cp_genericize_init_expr): Use iloc_sentinel.
            (cp_genericize_target_expr): Likewise.

    gcc/testsuite/ChangeLog:

            * g++.dg/debug/dwarf2/lineno-array1.C: New test.

[Bug debug/107154] [12 Regression] GDB jumping to end of block when stepping over construction of local variable

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[12/13 Regression] GDB      |[12 Regression] GDB jumping
                   |jumping to end of block     |to end of block when
                   |when stepping over          |stepping over construction
                   |construction of local       |of local variable
                   |variable                    |
   Target Milestone|---                         |12.3
           Priority|P3                          |P2
      Known to work|                            |13.0
      Known to fail|13.0                        |

[Bug debug/107154] [12 Regression] GDB jumping to end of block when stepping over construction of local variable

[cvs-commit at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

--- Comment #5 from CVS Commits <cvs-commit at gcc dot gnu.org> ---
The releases/gcc-12 branch has been updated by Jason Merrill
<jason@gcc.gnu.org>:

https://gcc.gnu.org/g:2088358b658c44f69d37af0d7deec321f557741d

commit r12-9430-g2088358b658c44f69d37af0d7deec321f557741d
Author: Jason Merrill <jason@redhat.com>
Date:   Tue Oct 4 17:06:04 2022 -0400

    c++: fix debug info for array temporary [PR107154]

    In the testcase the elaboration of the array init that happens at
genericize
    time was getting the location info for the end of the function; fixed by
    doing the expansion at the location of the original expression.

            PR c++/107154

    gcc/cp/ChangeLog:

            * cp-gimplify.cc (cp_genericize_init_expr): Use iloc_sentinel.
            (cp_genericize_target_expr): Likewise.

    gcc/testsuite/ChangeLog:

            * g++.dg/debug/dwarf2/lineno-array1.C: New test.

[Bug debug/107154] [12 Regression] GDB jumping to end of block when stepping over construction of local variable

[jason at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=107154

Jason Merrill <jason at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
         Resolution|---                         |FIXED
             Status|ASSIGNED                    |RESOLVED

--- Comment #6 from Jason Merrill <jason at gcc dot gnu.org> ---
Fixed for 12.3/13.