RE: [PATCHv2 6/6] gdb: convert the 'start' breakpoint to use inferior keyword

["Aktemur, Tankut Baris" <tankut.baris.aktemur@intel.com>]

On Friday, January 20, 2023 10:46 AM, Andrew Burgess wrote:
> Now that we have support for inferior specific breakpoints, the
> breakpoint created for the 'start' command can make use of this
> keyword.
> 
> In most cases the observed functionality should be unchanged from a
> user's point of view, though the code in GDB is a little cleaner now,
> we no longer need to change the expression used based on the
> language.
> 
> I do wonder if the current mechanism could run into problems if we had
> different inferiors of different languages.  For example, if we had an
> Ada inferior and a C inferior and followed a process a little like
> this:
> 
>   1. Start C inferior, the inferior stops before main for some reason,
> 
>   2. Start the Ada inferior, this runs to main,
> 
>   3. I think when we hit main, the condition for both breakpoints will
>   be evaluated, this will include evaluating the expression for the C
>   'start' breakpoint, which uses '==' and is, I guess, not valid for
>   Ada.
> 
> I haven't tried to create a testcase for this situation, but it's a
> possibly interesting edge case.
> 
> One place where the observed behaviour is different, is that inferior
> breakpoints, like thread breakpoints, will be auto-deleted when the
> contained inferior exits.
> 
> As a result, if an inferior exits before hitting the start breakpoint,
> then the 'start' breakpoint will be auto-deleted.
> 
> I have got a test that covers this situation.
> ---
>  gdb/infcmd.c                                  | 10 +---
>  .../gdb.base/start-inferior-specific-1.c      | 32 +++++++++++
>  .../gdb.base/start-inferior-specific-2.c      | 22 ++++++++
>  .../gdb.base/start-inferior-specific.exp      | 55 +++++++++++++++++++
>  4 files changed, 112 insertions(+), 7 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.base/start-inferior-specific-1.c
>  create mode 100644 gdb/testsuite/gdb.base/start-inferior-specific-2.c
>  create mode 100644 gdb/testsuite/gdb.base/start-inferior-specific.exp
> 
> diff --git a/gdb/infcmd.c b/gdb/infcmd.c
> index 7d5ec77ff57..7dfef4b5a23 100644
> --- a/gdb/infcmd.c
> +++ b/gdb/infcmd.c
> @@ -429,13 +429,9 @@ run_command_1 (const char *args, int from_tty, enum run_how run_how)
>  	 have proper inferior-specific breakpoint support, in the breakpoint
>  	 machinery.  We could then avoid inserting a breakpoint in the program
>  	 spaces unrelated to this inferior.  */
> -      const char *op
> -	= ((current_language->la_language == language_ada
> -	    || current_language->la_language == language_pascal
> -	    || current_language->la_language == language_m2) ? "=" : "==");
> -      std::string arg = string_printf
> -	("-qualified %s if $_inferior %s %d", main_name (), op,
> -	 current_inferior ()->num);
> +      std::string arg = string_printf ("-qualified %s inferior %d",
> +				       main_name (),
> +				       current_inferior ()->num);
>        tbreak_command (arg.c_str (), 0);
>      }
> 
> diff --git a/gdb/testsuite/gdb.base/start-inferior-specific-1.c
> b/gdb/testsuite/gdb.base/start-inferior-specific-1.c
> new file mode 100644
> index 00000000000..1717a82b75d
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/start-inferior-specific-1.c
> @@ -0,0 +1,32 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2022 Free Software Foundation, Inc.

2022-2023

> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +#include <unistd.h>
> +#include <stdlib.h>
> +
> +__attribute__((constructor))
> +static void
> +ctor (void)
> +{
> +  exit (1);
> +}
> +
> +int
> +main ()
> +{
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/start-inferior-specific-2.c
> b/gdb/testsuite/gdb.base/start-inferior-specific-2.c
> new file mode 100644
> index 00000000000..b69e218962a
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/start-inferior-specific-2.c
> @@ -0,0 +1,22 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2022 Free Software Foundation, Inc.

2022-2023

> +
> +   This program is free software; you can redistribute it and/or modify
> +   it under the terms of the GNU General Public License as published by
> +   the Free Software Foundation; either version 3 of the License, or
> +   (at your option) any later version.
> +
> +   This program is distributed in the hope that it will be useful,
> +   but WITHOUT ANY WARRANTY; without even the implied warranty of
> +   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
> +   GNU General Public License for more details.
> +
> +   You should have received a copy of the GNU General Public License
> +   along with this program.  If not, see <http://www.gnu.org/licenses/>.  */
> +
> +int
> +main ()
> +{
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/start-inferior-specific.exp
> b/gdb/testsuite/gdb.base/start-inferior-specific.exp
> new file mode 100644
> index 00000000000..7271f6d49d3
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/start-inferior-specific.exp
> @@ -0,0 +1,55 @@
> +# Copyright 2022 Free Software Foundation, Inc.

2022-2023

Regards,
-Baris


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