[Bug c++/106820] internal compiler error: in function_and_variable_visibility [for std::shared_ptr<data>{b,??} use via <memory> module]

["markmigm at gmail dot com" <gcc-bugzilla@gcc.gnu.org>]

https://gcc.gnu.org/bugzilla/show_bug.cgi?id=106820

--- Comment #4 from Mark Millard <markmigm at gmail dot com> ---
(In reply to Mark Millard from comment #3)

> . . .
> And in a debugger I see:
> 
> (lldb) print node->decl->decl_with_vis.weak_flag
> (unsigned int) $2 = 1
> (lldb) print node->decl->decl_with_vis.comdat_flag
> (unsigned int) $3 = 0
> (lldb) print node->weakref
> (unsigned int) $4 = 0
> (lldb) print node->decl->decl_common.decl_flag_1
> (unsigned int) $5 = 0
> 
> and:
> 
> (lldb) call debug_tree(node->decl)
>  <function_decl 0x9986ca00 __gthrw_pthread_mutex_unlock
>     type <function_type 0x939e7e70
>         type <integer_type 0x8cd415e8 int sizes-gimplified public type_6 SI
>             size <integer_cst 0x8cd40258 constant 32>
>             unit-size <integer_cst 0x8cd40270 constant 4>
>             align:32 warn_if_not_align:0 symtab:0 alias-set -1
> canonical-type 0x8cd415e8 precision:32 min <integer_cst 0x8cd40210
> -2147483648> max <integer_cst 0x8cd40228 2147483647>
>             pointer_to_this <pointer_type 0x8cd48a80> reference_to_this
> <reference_type 0x9bb63000>>
>         SI size <integer_cst 0x8cd40258 32> unit-size <integer_cst
> 0x8cd40270 4>
>         align:32 warn_if_not_align:0 symtab:0 alias-set -1 canonical-type
> 0x939e7f18
>         arg-types <tree_list 0x9986d168 value <pointer_type 0x939e7a80>
>             chain <tree_list 0x8cd2b938 value <void_type 0x8cd41f18 void>>>
>         pointer_to_this <pointer_type 0x99870150>>
>     addressable used static tree_3 weak in_system_header decl_5 decl_6 DI
> /usr/local/lib/gcc12/include/c++/aarch64-portbld-freebsd14.0/bits/gthr-
> default.h:121:1 align:32 warn_if_not_align:0 context <translation_unit_decl
> 0x8cd3e000 module_shared_ptr_alias_construction_failure.cpp>
>     attributes <tree_list 0x9986d230
>         purpose <identifier_node 0x939ca980 alias
>             normal local bindings <0x0>>
>         value <tree_list 0x9986d258
>             value <string_cst 0x939c6d80 type <array_type 0x939e77e0>
>                 readonly constant static "pthread_mutex_unlock\000">>
>         chain <tree_list 0x9986d280
>             purpose <identifier_node 0x939ca9c0 weakref
>                 normal local bindings <0x0>>>>
>     full-name "int __gthrw_pthread_mutex_unlock(pthread_mutex**)"
>     module 1:/usr/local/lib/gcc12/include/c++/memory exported chain
> <function_decl 0x9986c900 __gthread_trigger>>

And, sure enough, __gthrw_pthread_mutex_unlock looks to involve "weak" via
https://github.com/gcc-mirror/gcc/blob/master/libgcc/gthr-posix.h having
in use:

# define __gthrw2(name,name2,type) \
  static __typeof(type) name \
    __attribute__ ((__weakref__(#name2), __copy__ (type))); \
  __gthrw_pragma(weak type)
. . .
/* Typically, __gthrw_foo is a weak reference to symbol foo.  */
#define __gthrw(name) __gthrw2(__gthrw_ ## name,name,name)
. . .
__gthrw(pthread_mutex_unlock)

There could be more examples of the type of issue but the build stops
at the first to fail the gcc_assert.