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

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

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.

gdb/ChangeLog:

2020-06-03  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:

2020-06-03  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.