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

["Willgerodt, Felix" <felix.willgerodt@intel.com>]

> -----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
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