memory increased rapidly when adding a break

Hi,

I compiled envoy(a big c++ project) by using gcc-12.2.0, debug it by using
gdb 12.1.

But, memory increased rapidly(over 40+GB, until OOM), when adding a break.

I got this backtrace, after attach the gdb process, when memory increasing.

```
(gdb) bt
#0  0x00007fa6893dc935 in _int_malloc () from /lib64/libc.so.6
#1  0x00007fa6893df6fc in malloc () from /lib64/libc.so.6
#2  0x0000000000468278 in xmalloc (size=4064) at alloc.c:60
#3  0x00000000008ecd95 in call_chunkfun (size=<optimized out>,
h=0x17a246ed0) at ./obstack.c:94
#4  _obstack_begin_worker (h=0x17a246ed0, size=<optimized out>,
alignment=<optimized out>) at ./obstack.c:141
#5  0x000000000052d0d3 in demangle_parse_info::demangle_parse_info
(this=0x17a246ec0) at cp-name-parser.y:1973
#6  cp_demangled_name_to_comp (demangled_name=demangled_name@entry=0x8d12c8c0
"std::stack<unsigned int, std::deque<unsigned int, std::allocator<unsigned
int> > >::size_type", errmsg=errmsg@entry=0x0) at cp-name-parser.y:2040
#7  0x000000000052ff5e in cp_canonicalize_string
(string=string@entry=0x8d12c8c0
"std::stack<unsigned int, std::deque<unsigned int, std::allocator<unsigned
int> > >::size_type") at cp-support.c:635
#8  0x0000000000570b98 in dwarf2_canonicalize_name (name=0x8d12c8c0
"std::stack<unsigned int, std::deque<unsigned int, std::allocator<unsigned
int> > >::size_type", cu=<optimized out>, objfile=0x2c3af10) at
dwarf2/read.c:22908
#9  0x0000000000590265 in dwarf2_compute_name (name=0x7fa55773c524
"size_type", die=0x172590eb0, cu=0xe2aeefd0, physname=0) at
dwarf2/read.c:10095
#10 0x000000000058bf39 in dwarf2_full_name (cu=0xe2aeefd0, die=0x172590eb0,
name=0x0) at dwarf2/read.c:10123
#11 read_typedef (cu=0xe2aeefd0, die=0x172590eb0) at dwarf2/read.c:17687
#12 read_type_die_1 (cu=0xe2aeefd0, die=0x172590eb0) at dwarf2/read.c:22531
#13 read_type_die (die=0x172590eb0, cu=0xe2aeefd0) at dwarf2/read.c:22473
#14 0x000000000059acda in dwarf2_add_type_defn (cu=0xe2aeefd0,
die=0x172590eb0, fip=0x7ffd8a1be3e0) at dwarf2/read.c:14740
#15 handle_struct_member_die (child_die=0x172590eb0, type=0x17a6becd0,
fi=0x7ffd8a1be3e0, template_args=<optimized out>, cu=0xe2aeefd0) at
dwarf2/read.c:15867
#16 0x0000000000597044 in process_structure_scope (cu=0xe2aeefd0,
die=0x172590920) at dwarf2/read.c:15908
#17 process_die (die=0x172590920, cu=0xe2aeefd0) at dwarf2/read.c:9698
#18 0x000000000059646d in read_namespace (cu=0xe2aeefd0, die=0x16802e140)
at dwarf2/read.c:17068
#19 process_die (die=0x16802e140, cu=0xe2aeefd0) at dwarf2/read.c:9737
#20 0x0000000000598df9 in read_file_scope (die=0x1594e8360, cu=0xe2aeefd0)
at dwarf2/read.c:10648
#21 0x0000000000595f32 in process_die (die=0x1594e8360, cu=0xe2aeefd0) at
dwarf2/read.c:9669
#22 0x000000000059c0c8 in process_full_comp_unit
(pretend_language=<optimized out>, cu=0xe2aeefd0) at dwarf2/read.c:9439
#23 process_queue (per_objfile=0x9d546c0) at dwarf2/read.c:8652
#24 dw2_do_instantiate_symtab (per_cu=<optimized out>,
per_objfile=0x9d546c0, skip_partial=<optimized out>) at dwarf2/read.c:2311
#25 0x000000000059c5f0 in dw2_instantiate_symtab (per_cu=0x9c886f0,
per_objfile=0x9d546c0, skip_partial=<optimized out>) at
dwarf2/read.c:2335#26 0x000000000059c78a in
dw2_expand_symtabs_matching_one(dwarf2_per_cu_data *, dwarf2_per_objfile *,
gdb::function_view<bool(char const*, bool)>,
gdb::function_view<bool(compunit_symtab*)>) (per_cu=<optimized out>,
per_objfile=<optimized out>, file_matcher=..., expansion_notify=...) at
dwarf2/read.c:4204
#27 0x000000000059c94b in
dwarf2_gdb_index::expand_symtabs_matching(objfile*, gdb::function_view<bool
(char const*, bool)>, lookup_name_info const*, gdb::function_view<bool
(char const*)>, gdb::function_view<bool (compunit_symtab*)>,
enum_flags<block_search_flag_values>, domain_enum_tag, search_domain)
(this=<optimized out>, objfile=<optimized out>, file_matcher=...,
lookup_name=<optimized out>, symbol_matcher=
..., expansion_notify=..., search_flags=..., domain=UNDEF_DOMAIN,
kind=<optimized out>) at dwarf2/read.c:4421
#28 0x0000000000730feb in objfile::map_symtabs_matching_filename(char
const*, char const*, gdb::function_view<bool (symtab*)>) (this=0x2c3af10,
name=<optimized out>, name@entry=0x586f26f0 "utility.h",
real_path=<optimized out>, real_path@entry=0x0, callback=...) at
symfile-debug.c:207
#29 0x0000000000741abd in iterate_over_symtabs(char const*,
gdb::function_view<bool (symtab*)>) (name=name@entry=0x586f26f0
"utility.h", callback=...) at symtab.c:624
#30 0x00000000006311d7 in collect_symtabs_from_filename (file=0x586f26f0
"utility.h", search_pspace=<optimized out>) at linespec.c:3716
#31 0x0000000000631212 in symtabs_from_filename (filename=0x586f26f0
"utility.h", search_pspace=<optimized out>) at linespec.c:3736
#32 0x0000000000635e9f in parse_linespec (parser=0x7ffd8a1bf1b0,
arg=<optimized out>, match_type=<optimized out>) at linespec.c:2557
#33 0x0000000000636cac in event_location_to_sals (parser=0x7ffd8a1bf1b0,
location=0x51ed4da0) at linespec.c:3082
#34 0x0000000000636f73 in decode_line_full (location=location@entry=0x51ed4da0,
flags=flags@entry=1, search_pspace=search_pspace@entry=0x0,
default_symtab=<optimized out>, default_line=<optimized out>,
canonical=0x7ffd8a1bf4e0, select_mode=0x0, filter=<optimized out>) at
linespec.c:3161
#35 0x00000000004b1683 in parse_breakpoint_sals (location=0x51ed4da0,
canonical=0x7ffd8a1bf4e0) at breakpoint.c:8730
#36 0x00000000004b5d03 in create_breakpoint (gdbarch=0xeca5dc0,
location=location@entry=0x51ed4da0, cond_string=cond_string@entry=0x0,
thread=<optimized out>, thread@entry=-1, extra_string=0x0,
extra_string@entry=0x7ffd8a1bf650 "",
force_condition=force_condition@entry=false,
parse_extra=0, tempflag=0, type_wanted=bp_breakpoint, ignore_count=0,
pending_break_support=AUTO_BOOLEAN_TRUE, ops=0xc23c00
<bkpt_breakpoint_ops>, from_tty=0, enabled=1, internal=0, flags=0) at
breakpoint.c:9009
#37 0x0000000000674ba8 in mi_cmd_break_insert_1 (dprintf=0, argv=<optimized
out>, argc=<optimized out>, command=<optimized out>) at
mi/mi-cmd-break.c:361
```

Also, I found it's loop in `dwarf2_gdb_index::expand_symtabs_matching`.
I added a break on `dw2_expand_symtabs_matching_one`, it hit this break
repeatly.

```
  if (lookup_name == nullptr)
    {
      for (dwarf2_per_cu_data *per_cu
        : all_comp_units_range (per_objfile->per_bfd))
      {
         QUIT;
         if (!dw2_expand_symtabs_matching_one (per_cu, per_objfile,
file_matcher, expansion_notify))
           return false;
      }
      return true;
    }
```

Seems, `per_bfd->all_comp_units.size()` is `28776`.
I'm not sure if this is a reasonable value.

```
(gdb) p per_objfile->per_bfd->all_comp_units
$423 = {<std::_Vector_base<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter>,
std::allocator<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter> > >> = {_M_impl =
{<std::allocator<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter> >> =
{<__gnu_cxx::new_allocator<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter> >> = {<No data fields>}, <No data fields>},
<std::_Vector_base<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter>,
std::allocator<std::unique_ptr<dwarf2_per_cu_data,
dwarf2_per_cu_data_deleter> > >::_Vector_impl_data> = {_M_start =
0x3b6f980, _M_finish = 0x3b769e8, _M_end_of_storage = 0x3b769e8}, <No data
fields>}}, <No data fields>}
(gdb) p 0x3b769e8-0x3b6f980
$424 = 28776
```

I can see the memory increasing rapidly in the for loop.
I'm new to the gdb internal implementation.
I'm not sure where could be the problem, gcc or gdb, or just a wrong use.

Could you help to point the direction? I have the files to reproduce it
stablely.
Thanks a bot!

gcc version:
```
gcc -v
Using built-in specs.
COLLECT_GCC=gcc
COLLECT_LTO_WRAPPER=/home/
zhudejiang.pt/work/gcc-12/libexec/gcc/x86_64-pc-linux-gnu/12.2.0/lto-wrapper
Target: x86_64-pc-linux-gnu
Configured with: ./configure --prefix=/home/zhudejiang.pt/work/gcc-12/
--with-gmp=/home/zhudejiang.pt/work/gnu/gmp --with-mpfr=/home/
zhudejiang.pt/work/gnu/mpfr --with-mpfr-lib=/home/
zhudejiang.pt/work/gnu/mpfr/lib --with-mpc=/home/zhudejiang.pt/work/gnu/mpc
--disable-multilib
Thread model: posix
Supported LTO compression algorithms: zlib
gcc version 12.2.0 (GCC)
```

gdb version:
```
gdb -v
GNU gdb (GDB) 12.1
Copyright (C) 2022 Free Software Foundation, Inc.
License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html
>
This is free software: you are free to change and redistribute it.
There is NO WARRANTY, to the extent permitted by law.
```