RE: [PATCH 1/1] gdb: Avoid warning for the jump command inside an inline function.

[Andrew Burgess <aburgess@redhat.com>]

"Willgerodt, Felix" <felix.willgerodt@intel.com> writes:

>> -----Original Message-----
>> From: Willgerodt, Felix
>> Sent: Dienstag, 25. April 2023 16:40
>> To: Andrew Burgess <aburgess@redhat.com>; gdb-
>> patches@sourceware.org
>> Subject: RE: [PATCH 1/1] gdb: Avoid warning for the jump command inside an
>> inline function.
>> 
>> > -----Original Message-----
>> > From: Andrew Burgess <aburgess@redhat.com>
>> > Sent: Dienstag, 25. April 2023 16:09
>> > To: Felix Willgerodt via Gdb-patches <gdb-patches@sourceware.org>; gdb-
>> > patches@sourceware.org
>> > Cc: Willgerodt, Felix <felix.willgerodt@intel.com>; Cristian Sandu
>> > <cristian.sandu@intel.com>
>> > Subject: Re: [PATCH 1/1] gdb: Avoid warning for the jump command inside
>> > an inline function.
>> >
>> > Felix Willgerodt via Gdb-patches <gdb-patches@sourceware.org> writes:
>> >
>> > > When stopped inside an inline function, trying to jump to a different line
>> > > of the same function currently results in a warning about jumping to
>> > another
>> > > function.  Fix this by taking inline functions into account.
>> > >
>> > > Before:
>> > >   Breakpoint 1, function_inline (x=510) at jump-inline.cpp:22
>> > >   22        a = a + x;             /* inline-funct */
>> > >   (gdb) j 21
>> > >   Line 21 is not in `function_inline(int)'.  Jump anyway? (y or n)
>> > >
>> > > After:
>> > >   Breakpoint 2, function_inline (x=510) at jump-inline.cpp:22
>> > >   22        a = a + x;            /* inline-funct */
>> > >   (gdb) j 21
>> > >   Continuing at 0x400679.
>> > >
>> > >   Breakpoint 1, function_inline (x=510) at jump-inline.cpp:21
>> > >   21        a += 1020 + a;                /* increment-funct */
>> > >
>> > > This was regression-tested on X86-64 Linux.
>> > >
>> > > Co-Authored-by: Cristian Sandu <cristian.sandu@intel.com>
>> > > ---
>> > >  gdb/infcmd.c                           |  3 +-
>> > >  gdb/testsuite/gdb.base/jump-inline.c   | 30 +++++++++++++++++
>> > >  gdb/testsuite/gdb.base/jump-inline.exp | 45
>> > ++++++++++++++++++++++++++
>> > >  3 files changed, 77 insertions(+), 1 deletion(-)
>> > >  create mode 100644 gdb/testsuite/gdb.base/jump-inline.c
>> > >  create mode 100644 gdb/testsuite/gdb.base/jump-inline.exp
>> > >
>> > > diff --git a/gdb/infcmd.c b/gdb/infcmd.c
>> > > index fd88b8ca328..40414bc9260 100644
>> > > --- a/gdb/infcmd.c
>> > > +++ b/gdb/infcmd.c
>> > > @@ -1091,7 +1091,8 @@ jump_command (const char *arg, int from_tty)
>> > >
>> > >    /* See if we are trying to jump to another function.  */
>> > >    fn = get_frame_function (get_current_frame ());
>> > > -  sfn = find_pc_function (sal.pc);
>> > > +  sfn = find_pc_sect_containing_function (sal.pc,
>> > > +					  find_pc_mapped_section (sal.pc));
>> >
>> > I had a read through the discussion about whether find_pc_function
>> > should return inline functions or not.  I don't know the history of this
>> > code, so I don't know if there's a reason why it does what it does, but
>> > looking at how it's used, I know there are some places in GDB where
>> > find_pc_function is used when it shouldn't be.
>> >
>> > For example in edit_command (cli-cmds.c) I'm pretty sure the use of
>> > find_pc_function is incorrect -- GDB will print the name of the
>> > containing function, but then open the editor on the inlined function.
>> >
>> > As was said elsewhere, the biggest problem here will be lack of
>> > testing.  What is really needed is an audit of each use of
>> > find_pc_function and to ensure that each use is hit with an inline
>> > function and a non-inline function.  Until then I think it's hard to be
>> > certain about whether find_pc_function can safely be changed or not.
>> > But doing that is no small task.
>> >
>> > Given that, I'm inclined to think we should take the patch as
>> > presented.  If anyone ever does get around to sorting out this corner of
>> > GDB then it's easy enough to revert this code back to use
>> > find_pc_function.
>> >
>> > I do have one minor nit though...
>> >
>> > >    if (fn != nullptr && sfn != fn)
>> > >      {
>> > >        if (!query (_("Line %d is not in `%s'.  Jump anyway? "), sal.line,
>> > > diff --git a/gdb/testsuite/gdb.base/jump-inline.c
>> > b/gdb/testsuite/gdb.base/jump-inline.c
>> > > new file mode 100644
>> > > index 00000000000..17447c2d557
>> > > --- /dev/null
>> > > +++ b/gdb/testsuite/gdb.base/jump-inline.c
>> > > @@ -0,0 +1,30 @@
>> > > +/* Copyright 2021-2023 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 2 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/>.
>> > */
>> > > +
>> > > +__attribute__((always_inline))
>> > > +static void inline
>> > > +function_inline (int x)
>> > > +{
>> > > +  int a = x;
>> > > +  a += 1020 + a;		/* increment-funct. */
>> > > +  a = a + x;			/* inline-funct. */
>> > > +}
>> > > +
>> > > +int
>> > > +main ()
>> > > +{
>> > > +  function_inline (510);
>> > > +  return 0;			/* out-of-func. */
>> > > +}
>> > > diff --git a/gdb/testsuite/gdb.base/jump-inline.exp
>> > b/gdb/testsuite/gdb.base/jump-inline.exp
>> > > new file mode 100644
>> > > index 00000000000..fef29fedb2f
>> > > --- /dev/null
>> > > +++ b/gdb/testsuite/gdb.base/jump-inline.exp
>> > > @@ -0,0 +1,45 @@
>> > > +# Copyright 2021-2023 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/>.
>> > */
>> > > +#
>> > > +# Tests GDBs support for jump for inline functions.
>> > > +
>> > > +standard_testfile
>> > > +
>> > > +if { [prepare_for_testing "failed to prepare" $testfile $srcfile] } {
>> > > +    return -1
>> > > +}
>> > > +
>> > > +if { ![runto_main] } {
>> > > +    untested "failed to run to main"
>> >
>> > This untested line is not needed.  runto_main will emit a FAIL if
>> > anything goes wrong.
>> 
>> Right, I will remove it.
>> 
>> > Reviewed-By: Andrew Burgess <aburgess@redhat.com>
>> >
>> > Thanks,
>> > Andrew
>> 
>> Thank you for your review and thorough feedback. I agree with your
>> thoughts and conclusion.
>> I am wondering though, as you gave me a reviewed-by but not an
>> approved-by, should I wait a bit more or can I push this? I posted it originally
>> in January and pinged a few times. So I tend to think that waiting more isn't
>> worth it, but I am of course fine with doing that.
>> 
>> Thanks,
>> Felix
>
> *Pinging again after 10 days of no further comments*
>
> Is it okay to push this with the untested line removed?

As nobody has complained:

Approved-By: Andrew Burgess <aburgess@redhat.com>

Thanks,
Andrew


>
> Thanks,
> Felix
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