Re: [PATCH][gdb/symtab] Fix missing breakpoint location for inlined function

[Tom de Vries <tdevries@suse.de>]

On 27-05-2020 12:37, Tom de Vries wrote:
> Hi,
> 
> Consider the test-case contained in this patch.
> 
> With -readnow, we have two breakpoint locations:
> ...
> $ gdb -readnow -batch breakpoint-locs -ex "b N1::C1::baz" -ex "info break"
> Breakpoint 1 at 0x4004cb: N1::C1::baz. (2 locations)
> Num     Type           Disp Enb Address            What
> 1       breakpoint     keep y   <MULTIPLE>
> 1.1                         y   0x00000000004004cb in N1::C1::baz() \
>                                                      at breakpoint-locs.h:6
> 1.2                         y   0x00000000004004f0 in N1::C1::baz() \
>                                                      at breakpoint-locs.h:6
> ...
> 
> But without -readnow, we have instead only one breakpoint location:
> ...
> $ gdb -batch breakpoint-locs -ex "b N1::C1::baz" -ex "info break"
> Breakpoint 1 at 0x4004f0: file breakpoint-locs.h, line 6.
> Num     Type           Disp Enb Address            What
> 1       breakpoint     keep y   0x00000000004004f0 in N1::C1::baz() \
>                                                      at breakpoint-locs.h:6
> ...
> 
> The relevant dwarf is this bit:
> ...
>  <0><d2>: Abbrev Number: 1 (DW_TAG_compile_unit)
>     <d8>   DW_AT_name        : breakpoint-locs.cc
>  <1><f4>: Abbrev Number: 2 (DW_TAG_namespace)
>     <f5>   DW_AT_name        : N1
>  <2><fe>: Abbrev Number: 3 (DW_TAG_class_type)
>     <ff>   DW_AT_name        : C1
>  <3><109>: Abbrev Number: 4 (DW_TAG_subprogram)
>     <10a>   DW_AT_name        : baz
>     <110>   DW_AT_linkage_name: _ZN2N12C13bazEv
>  <2><116>: Abbrev Number: 5 (DW_TAG_subprogram)
>     <117>   DW_AT_name        : foo
>     <11d>   DW_AT_linkage_name: _ZN2N13fooEv
>  <1><146>: Abbrev Number: 8 (DW_TAG_subprogram)
>     <147>   DW_AT_specification: <0x116>
>     <14b>   DW_AT_low_pc      : 0x4004c7
>     <153>   DW_AT_high_pc     : 0x10
>  <2><161>: Abbrev Number: 9 (DW_TAG_inlined_subroutine)
>     <162>   DW_AT_abstract_origin: <0x194>
>     <166>   DW_AT_low_pc      : 0x4004cb
>     <16e>   DW_AT_high_pc     : 0x9
>  <1><194>: Abbrev Number: 12 (DW_TAG_subprogram)
>     <195>   DW_AT_specification: <0x109>
>     <199>   DW_AT_inline      : 3       (declared as inline and inlined)
> ...
> 
> The missing breakpoint location is specified by DIE 0x161, which is ignored by
> the partial DIE reader because it's a child of a DW_TAG_subprogram DIE (at
> 0x146, for foo).
> 
> Fix this by not ignoring the DIE during partial DIE reading.
> 
> Tested on x86_64-linux.
> 
> Any comments?
> 

I've pushed this patch (after adding missing copyright notices).

Thanks,
- Tom

> [gdb/symtab] Fix missing breakpoint location for inlined function
> 
> gdb/ChangeLog:
> 
> 2020-05-27  Tom de Vries  <tdevries@suse.de>
> 
> 	PR symtab/26046
> 	* dwarf2/read.c (scan_partial_symbols): Recurse into DW_TAG_subprogram
> 	children for C++.
> 	(load_partial_dies): Don't skip DW_TAG_inlined_subroutine child of
> 	DW_TAG_subprogram.
> 
> gdb/testsuite/ChangeLog:
> 
> 2020-05-27  Tom de Vries  <tdevries@suse.de>
> 
> 	PR symtab/26046
> 	* gdb.cp/breakpoint-locs-2.cc: New test.
> 	* gdb.cp/breakpoint-locs.cc: New test.
> 	* gdb.cp/breakpoint-locs.exp: New file.
> 	* gdb.cp/breakpoint-locs.h: New test.
> 
> ---
>  gdb/dwarf2/read.c                         |  6 +++++-
>  gdb/testsuite/gdb.cp/breakpoint-locs-2.cc | 12 ++++++++++++
>  gdb/testsuite/gdb.cp/breakpoint-locs.cc   | 16 ++++++++++++++++
>  gdb/testsuite/gdb.cp/breakpoint-locs.exp  | 27 +++++++++++++++++++++++++++
>  gdb/testsuite/gdb.cp/breakpoint-locs.h    |  8 ++++++++
>  5 files changed, 68 insertions(+), 1 deletion(-)
> 
> diff --git a/gdb/dwarf2/read.c b/gdb/dwarf2/read.c
> index ec3844188e..7ab521a656 100644
> --- a/gdb/dwarf2/read.c
> +++ b/gdb/dwarf2/read.c
> @@ -8054,6 +8054,9 @@ scan_partial_symbols (struct partial_die_info *first_die, CORE_ADDR *lowpc,
>  	    case DW_TAG_subprogram:
>  	    case DW_TAG_inlined_subroutine:
>  	      add_partial_subprogram (pdi, lowpc, highpc, set_addrmap, cu);
> +	      if (cu->language == language_cplus)
> +		scan_partial_symbols (pdi->die_child, lowpc, highpc,
> +				      set_addrmap, cu);
>  	      break;
>  	    case DW_TAG_constant:
>  	    case DW_TAG_variable:
> @@ -18125,7 +18128,8 @@ load_partial_dies (const struct die_reader_specs *reader,
>        if (!load_all
>  	  && cu->language == language_cplus
>  	  && parent_die != NULL
> -	  && parent_die->tag == DW_TAG_subprogram)
> +	  && parent_die->tag == DW_TAG_subprogram
> +	  && abbrev->tag != DW_TAG_inlined_subroutine)
>  	{
>  	  info_ptr = skip_one_die (reader, info_ptr + bytes_read, abbrev);
>  	  continue;
> diff --git a/gdb/testsuite/gdb.cp/breakpoint-locs-2.cc b/gdb/testsuite/gdb.cp/breakpoint-locs-2.cc
> new file mode 100644
> index 0000000000..0bce5caa93
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/breakpoint-locs-2.cc
> @@ -0,0 +1,12 @@
> +#include "breakpoint-locs.h"
> +
> +namespace N1
> +{
> +  void bar () { C1::baz (); }
> +}
> +
> +void
> +N1_bar (void)
> +{
> +  N1::bar ();
> +}
> diff --git a/gdb/testsuite/gdb.cp/breakpoint-locs.cc b/gdb/testsuite/gdb.cp/breakpoint-locs.cc
> new file mode 100644
> index 0000000000..e73e721335
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/breakpoint-locs.cc
> @@ -0,0 +1,16 @@
> +#include "breakpoint-locs.h"
> +
> +namespace N1
> +{
> +  void foo () { C1::baz (); }
> +}
> +
> +extern void N1_bar (void);
> +
> +int
> +main ()
> +{
> +  N1::foo ();
> +  N1_bar ();
> +  return 0;
> +}
> diff --git a/gdb/testsuite/gdb.cp/breakpoint-locs.exp b/gdb/testsuite/gdb.cp/breakpoint-locs.exp
> new file mode 100644
> index 0000000000..46b64e9de6
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/breakpoint-locs.exp
> @@ -0,0 +1,27 @@
> +# 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/>.
> +
> +# This file is part of the gdb testsuite
> +
> +if {[skip_cplus_tests]} { continue }
> +
> +standard_testfile .cc breakpoint-locs-2.cc
> +
> +if { [prepare_for_testing "failed to prepare" $testfile "$srcfile $srcfile2"\
> +	  {debug c++}] } {
> +    return -1
> +}
> +
> +gdb_test "break N1::C1::baz" "\\(2 locations\\)"
> diff --git a/gdb/testsuite/gdb.cp/breakpoint-locs.h b/gdb/testsuite/gdb.cp/breakpoint-locs.h
> new file mode 100644
> index 0000000000..52c2b8d84e
> --- /dev/null
> +++ b/gdb/testsuite/gdb.cp/breakpoint-locs.h
> @@ -0,0 +1,8 @@
> +namespace N1
> +{
> +  class C1
> +  {
> +   public:
> +    static void __attribute__((always_inline)) baz () { volatile unsigned i; i++; }
> +  };
> +}
>