Re: [PATCH v3] inferior without argument prints detail of current inferior

[Simon Marchi via Gdb-patches <gdb-patches@sourceware.org>]

On 2021-01-09 4:24 p.m., Lancelot SIX via Gdb-patches wrote:
> This patch makes the inferior command display information about the
> current inferior when called with no argument. This behavior is similar
> to the one of the thread command.
> 
> This contribution is inspired by an item in
> https://sourceware.org/gdb/wiki/ProjectIdeas
> 
> Before patch:
> 
>     (gdb) info inferior
>       Num  Description       Connection           Executable
>     * 1    process 19221     1 (native)           /home/lsix/tmp/a.out
>       2    process 19239     1 (native)           /home/lsix/tmp/a.out
>     (gdb) inferior 2
>     [Switching to inferior 2 [process 19239] (/home/lsix/tmp/a.out)]
>     [Switching to thread 2.1 (process 19239)]
>     #0  0x0000000000401146 in main ()
>     (gdb) inferior
>     Argument required (expression to compute).
> 
> After patch:
> 
>     (gdb) info inferior
>       Num  Description       Connection           Executable
>     * 1    process 18699     1 (native)           /home/lsix/tmp/a.out
>       2    process 18705     1 (native)           /home/lsix/tmp/a.out
>     (gdb) inferior 2
>     [Switching to inferior 2 [process 18705] (/home/lsix/tmp/a.out)]
>     [Switching to thread 2.1 (process 18705)]
>     #0  0x0000000000401146 in main ()
>     (gdb) inferior
>     [Current inferior is 2 [process 18705] (/home/lsix/tmp/a.out)]
> 
> Changes from V1:
>   * Add test.
> 
> Change from V2:
>   * Fix gdb/doc/ChangeLog entry.
>   * My copyright assignment has been signed.
> 
> gdb/doc/ChangeLog:
> 
> 	* gdb.texinfo (Inferiors Connections and Programs): Document the
> 	inferior command when used without argument.
> 
> gdb/ChangeLog:
> 
> 	* inferior.c (inferior_command): When no argument is given to the
> 	inferior command, display info about the currently selected
> 	inferior.
> 
> gdb/testsuite/ChangeLog:
> 
> 	* gdb.base/inferior-noarg.c: New test.
> 	* gdb.base/inferior-noarg.exp: New test.
> 
> ---
> ---
>  gdb/doc/gdb.texinfo                       | 16 +++++++
>  gdb/inferior.c                            | 58 +++++++++++++++--------
>  gdb/testsuite/gdb.base/inferior-noarg.c   | 22 +++++++++
>  gdb/testsuite/gdb.base/inferior-noarg.exp | 36 ++++++++++++++
>  4 files changed, 111 insertions(+), 21 deletions(-)
>  create mode 100644 gdb/testsuite/gdb.base/inferior-noarg.c
>  create mode 100644 gdb/testsuite/gdb.base/inferior-noarg.exp
> 
> diff --git a/gdb/doc/gdb.texinfo b/gdb/doc/gdb.texinfo
> index 69fa6b709b..a97a342e9d 100644
> --- a/gdb/doc/gdb.texinfo
> +++ b/gdb/doc/gdb.texinfo
> @@ -3202,6 +3202,22 @@ For example,
>    2    process 2307      2 (extended-remote host:10000)  hello
>  @end smallexample
>  
> +To get informations about the current inferior, use @code{inferior}:
> +
> +@table @code
> +@kindex inferior
> +@item inferior
> +Shows information about the current inferior.
> +
> +For example,
> +@end table
> +@c end table here to get a little more width for example
> +
> +@smallexample
> +(@value{GDBP}) inferior
> +[Current inferior is 1 [process 3401] (helloworld)]
> +@end smallexample
> +
>  To find out what open target connections exist at any moment, use
>  @w{@code{info connections}}:
>  
> diff --git a/gdb/inferior.c b/gdb/inferior.c
> index 3ff0512c38..49f869a4c7 100644
> --- a/gdb/inferior.c
> +++ b/gdb/inferior.c
> @@ -635,34 +635,50 @@ inferior_command (const char *args, int from_tty)
>    struct inferior *inf;
>    int num;
>  
> -  num = parse_and_eval_long (args);
> -
> -  inf = find_inferior_id (num);
> -  if (inf == NULL)
> -    error (_("Inferior ID %d not known."), num);
> -
> -  if (inf->pid != 0)
> +  if (args == nullptr)
>      {
> -      if (inf != current_inferior ())
> -	{
> -	  thread_info *tp = any_thread_of_inferior (inf);
> -	  if (tp == NULL)
> -	    error (_("Inferior has no threads."));
> +      inf = current_inferior ();
> +      gdb_assert (inf != nullptr);
> +      const char *filename = inf->pspace->exec_filename.get ();
>  
> -	  switch_to_thread (tp);
> -	}
> +      if (filename == nullptr)
> +	filename = _("<noexec>");
>  
> -      gdb::observers::user_selected_context_changed.notify
> -	(USER_SELECTED_INFERIOR
> -	 | USER_SELECTED_THREAD
> -	 | USER_SELECTED_FRAME);
> +      printf_filtered (_("[Current inferior is %d [%s] (%s)]\n"),
> +		       inf->num, inferior_pid_to_str (inf->pid).c_str (),
> +		       filename);
>      }
>    else
>      {
> -      switch_to_inferior_no_thread (inf);
> +      num = parse_and_eval_long (args);
> +
> +      inf = find_inferior_id (num);
> +      if (inf == NULL)
> +	error (_("Inferior ID %d not known."), num);
> +
> +      if (inf->pid != 0)
> +	{
> +	  if (inf != current_inferior ())
> +	    {
> +	      thread_info *tp = any_thread_of_inferior (inf);
> +	      if (tp == NULL)
> +		error (_("Inferior has no threads."));
>  
> -      gdb::observers::user_selected_context_changed.notify
> -	(USER_SELECTED_INFERIOR);
> +	      switch_to_thread (tp);
> +	    }
> +
> +	  gdb::observers::user_selected_context_changed.notify
> +	    (USER_SELECTED_INFERIOR
> +	     | USER_SELECTED_THREAD
> +	     | USER_SELECTED_FRAME);
> +	}
> +      else
> +	{
> +	  switch_to_inferior_no_thread (inf);
> +
> +	  gdb::observers::user_selected_context_changed.notify
> +	    (USER_SELECTED_INFERIOR);
> +	}
>      }
>  }
>  
> diff --git a/gdb/testsuite/gdb.base/inferior-noarg.c b/gdb/testsuite/gdb.base/inferior-noarg.c
> new file mode 100644
> index 0000000000..9d7b2f1a4c
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/inferior-noarg.c
> @@ -0,0 +1,22 @@
> +/* This testcase is part of GDB, the GNU debugger.
> +
> +   Copyright 2020 Free Software Foundation, Inc.
> +
> +   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 (void)
> +{
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.base/inferior-noarg.exp b/gdb/testsuite/gdb.base/inferior-noarg.exp
> new file mode 100644
> index 0000000000..38842aa7d8
> --- /dev/null
> +++ b/gdb/testsuite/gdb.base/inferior-noarg.exp
> @@ -0,0 +1,36 @@
> +# Copyright 2020 Free Software Foundation, Inc.

Change both copyright years to 2021.

> +
> +# 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/>.
> +
> +# This test case checks that the 'inferior' command, when given no
> +# argument, displays information about the inferior currently active.
> +
> +standard_testfile
> +
> +if { [prepare_for_testing "failed to prepare" \
> +	${testfile} ${srcfile}] } {
> +    return
> +}
> +
> +gdb_test "inferior" "\[Current inferior is 1 \[<null>\] (.*)\]" "inferior not running"
> +
> +if { ![runto_main] } {
> +    untested "could not run to main"
> +    return
> +}
> +
> +gdb_test "inferior" "\[Current inferior is 1 \[process .*\] (.*)\]" "inferior running"

I'm worried that this regexp is a little bit too specific, as targets can
implement the `pid_to_str` method and decide to call their "process"
something else.  "process 1234" is just the default, done by normal_pid_to_str.

I'm fine with merging it though, as that will probably work with all in-tree
targets.  The only one I found where it wouldn't work in bsd_kvm_target, which
does:

std::string
bsd_kvm_target::pid_to_str (ptid_t ptid)
{
  return "<kvm>";
}

But I don't think the testsuite is ran against that target anywhere... and in
any case it's an easy fix if we stumble on a target for which it doesn't work.

Do you have push access?  If you plan on sending more patches, it would make
sense for you to have it, so you can push your own patches once approved.  Let
me know if you'd like to do that.

Simon