[Bug c++/111073] New: [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk

[Bug c++/111073] New: [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111073

            Bug ID: 111073
           Summary: [13/14 regression] False-positive -Wstringop-overflow
                    when building gdb from trunk
           Product: gcc
           Version: 14.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c++
          Assignee: unassigned at gcc dot gnu.org
          Reporter: sjames at gcc dot gnu.org
                CC: arsen at gcc dot gnu.org, tromey at gcc dot gnu.org
  Target Milestone: ---

Created attachment 55762
  --> https://gcc.gnu.org/bugzilla/attachment.cgi?id=55762&action=edit
infcall.ii.xz

12.3.1 20230818 is OK, but 13.2.1 20230812 and 14.0.0 20230813 aren't.

I filed this over at gdb first:
https://sourceware.org/bugzilla/show_bug.cgi?id=30780.

```
$ g++-14 -x c++    -I. -I. -I./config -DLOCALEDIR="\"/usr/local/share/locale\""
-DHAVE_CONFIG_H -I./../include/opcode -I../bfd -I./../bfd -I./../include
-I./../readline/readline/.. -I./../zlib  -I../libdecnumber -I./../libdecnumber 
-I./../gnulib/import -I../gnulib/import -I./.. -I.. -I./../libbacktrace/
-I../libbacktrace/ -DTUI=1    -I/usr/include/python3.12
-I/usr/include/python3.12   -I./.. -pthread    -Wall -Wpointer-arith
-Wno-unused -Wunused-value -Wunused-variable -Wunused-function -Wno-switch
-Wno-char-subscripts -Wempty-body -Wunused-but-set-parameter
-Wunused-but-set-variable -Wno-sign-compare -Wno-error=maybe-uninitialized
-Wno-mismatched-tags -Wsuggest-override -Wimplicit-fallthrough=3
-Wduplicated-cond -Wshadow=local -Wdeprecated-copy -Wdeprecated-copy-dtor
-Wredundant-move -Wmissing-declarations -Wstrict-null-sentinel -Wformat
-Wformat-nonliteral -Werror -g -O2     -c -o infcall.o -MT infcall.o -MMD -MP
-MF ./.deps/infcall.Tpo infcall.c
In file included from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/hashtable_policy.h:36,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/hashtable.h:35,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/unordered_map.h:33,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/unordered_map:41,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/functional:63,
                 from ./../gdbsupport/ptid.h:35,
                 from ./../gdbsupport/common-defs.h:206,
                 from defs.h:26,
                 from infcall.c:20:
In static member function ‘static _Up* std::__copy_move<_IsMove, true,
std::random_access_iterator_tag>::__copy_m(_Tp*, _Tp*, _Up*) [with _Tp =
value*; _Up = value*; bool _IsMove = false]’,
    inlined from ‘_OI std::__copy_move_a2(_II, _II, _OI) [with bool _IsMove =
false; _II = value**; _OI = value**]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:506:30,
    inlined from ‘_OI std::__copy_move_a1(_II, _II, _OI) [with bool _IsMove =
false; _II = value**; _OI = value**]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:533:42,
    inlined from ‘_OI std::__copy_move_a(_II, _II, _OI) [with bool _IsMove =
false; _II = value**; _OI = value**]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:540:31,
    inlined from ‘_OI std::copy(_II, _II, _OI) [with _II = value**; _OI =
value**]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:633:7,
    inlined from ‘static _ForwardIterator
std::__uninitialized_copy<true>::__uninit_copy(_InputIterator, _InputIterator,
_ForwardIterator) [with _InputIterator = value**; _ForwardIterator = value**]’
at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_uninitialized.h:147:27,
    inlined from ‘_ForwardIterator std::uninitialized_copy(_InputIterator,
_InputIterator, _ForwardIterator) [with _InputIterator = value**;
_ForwardIterator = value**]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_uninitialized.h:185:15,
    inlined from ‘_ForwardIterator std::__uninitialized_copy_a(_InputIterator,
_InputIterator, _ForwardIterator, allocator<_Tp>&) [with _InputIterator =
value**; _ForwardIterator = value**; _Tp = value*]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_uninitialized.h:373:37,
    inlined from ‘void std::vector<_Tp, _Alloc>::_M_range_insert(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = value**; _Tp = value*; _Alloc = std::allocator<value*>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/vector.tcc:884:38,
    inlined from ‘std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = value**; <template-parameter-2-2> = void; _Tp = value*; _Alloc
= std::allocator<value*>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_vector.h:1486:19,
    inlined from ‘value* call_function_by_hand_dummy(value*, type*,
gdb::array_view<value*>, void (*)(void*, int), void*)’ at infcall.c:1239:23:
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:437:30:
error: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ writing
9 or more bytes into a region of size 0 overflows the destination
[-Werror=stringop-overflow=]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
In file included from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/x86_64-pc-linux-gnu/bits/c++allocator.h:33,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/allocator.h:46,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/alloc_traits.h:39,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/ext/alloc_traits.h:34,
                 from
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/hashtable_policy.h:39:
In member function ‘_Tp* std::__new_allocator<_Tp>::allocate(size_type, const
void*) [with _Tp = value*]’,
    inlined from ‘static _Tp* std::allocator_traits<std::allocator<_Tp1>
>::allocate(allocator_type&, size_type) [with _Tp = value*]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/alloc_traits.h:482:28,
    inlined from ‘std::_Vector_base<_Tp, _Alloc>::pointer
std::_Vector_base<_Tp, _Alloc>::_M_allocate(std::size_t) [with _Tp = value*;
_Alloc = std::allocator<value*>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_vector.h:378:33,
    inlined from ‘void std::vector<_Tp, _Alloc>::_M_range_insert(iterator,
_ForwardIterator, _ForwardIterator, std::forward_iterator_tag) [with
_ForwardIterator = value**; _Tp = value*; _Alloc = std::allocator<value*>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/vector.tcc:875:40,
    inlined from ‘std::vector<_Tp, _Alloc>::iterator std::vector<_Tp,
_Alloc>::insert(const_iterator, _InputIterator, _InputIterator) [with
_InputIterator = value**; <template-parameter-2-2> = void; _Tp = value*; _Alloc
= std::allocator<value*>]’ at
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_vector.h:1486:19,
    inlined from ‘value* call_function_by_hand_dummy(value*, type*,
gdb::array_view<value*>, void (*)(void*, int), void*)’ at infcall.c:1239:23:
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/new_allocator.h:151:55:
note: at offset [-9223372036854775808, -1] into destination object of size [8,
9223372036854775800] allocated by ‘operator new’
  151 |         return static_cast<_Tp*>(_GLIBCXX_OPERATOR_NEW(__n *
sizeof(_Tp)));
      |                                                       ^
cc1plus: all warnings being treated as errors
```

[Bug c++/111073] [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111073

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
             Blocks|                            |88443

--- Comment #1 from Sam James <sjames at gcc dot gnu.org> ---
I can reproduce it with:
```
$ g++-14 -c infcall.ii -O2 -Werror=stringop-overflow
[...]
/usr/lib/gcc/x86_64-pc-linux-gnu/14/include/g++-v14/bits/stl_algobase.h:437:30:
error: ‘void* __builtin_memmove(void*, const void*, long unsigned int)’ writing
9 or more bytes into a region of size 0 overflows the destination
[-Werror=stringop-overflow=]
  437 |             __builtin_memmove(__result, __first, sizeof(_Tp) * _Num);
      |             ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
[...]
```


Referenced Bugs:

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=88443
[Bug 88443] [meta-bug] bogus/missing -Wstringop-overflow warnings

[Bug c++/111073] [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk with -D_GLIBCXX_ASSERTIONS

[sjames at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111073

Sam James <sjames at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
            Summary|[13/14 regression]          |[13/14 regression]
                   |False-positive              |False-positive
                   |-Wstringop-overflow when    |-Wstringop-overflow when
                   |building gdb from trunk     |building gdb from trunk
                   |                            |with -D_GLIBCXX_ASSERTIONS

--- Comment #2 from Sam James <sjames at gcc dot gnu.org> ---
Oh, interesting. It needs -D_GLIBCXX_ASSERTIONS (which my gcc has on by
default) to trigger.

[Bug tree-optimization/111073] [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk with -D_GLIBCXX_ASSERTIONS

[rguenth at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111073

Richard Biener <rguenth at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
   Target Milestone|---                         |13.3

[Bug tree-optimization/111073] [13/14 regression] False-positive -Wstringop-overflow when building gdb from trunk with -D_GLIBCXX_ASSERTIONS

[law at gcc dot gnu.org]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=111073

Jeffrey A. Law <law at gcc dot gnu.org> changed:

           What    |Removed                     |Added
----------------------------------------------------------------------------
           Priority|P3                          |P2
                 CC|                            |law at gcc dot gnu.org