[RTEMS Project] #4661: GCC 12 generates wrong code

[RTEMS trac]

#4661: GCC 12 generates wrong code
--------------------------+--------------------
  Reporter:  Chris Johns  |      Owner:  (none)
      Type:  defect       |     Status:  new
  Priority:  high         |  Milestone:  6.1
 Component:  tool/gcc     |    Version:  6
  Severity:  blocker      |   Keywords:
Blocked By:               |   Blocking:
--------------------------+--------------------
 Calling `exit()` in a C++ application results in `std::terminate()` being
 called.

 The `std::ios_base::Init::~Init()` destructor flushes `std::cout`,
 `std::cerr` and `std::clog`. The flush of `std::cerr` results in terminate
 being called.

 The `ios_base` class uses a sentry to check the state. The code in it's
 destructor is:
 {{{
 if (bool(_M_os.flags() & ios_base::unitbuf) && !uncaught_exception())
 }}}
 The `std::cerr` object has `ios_base::unitbuf` set so
 `uncaught_exception()` is called. This call gets the cxa globals:
 {{{
 __cxa_eh_globals *globals = __cxa_get_globals ();
 }}}
 The `__cxa_get_globals()` checks if the `ec_globals` `init` object:
 {{{
 static __eh_globals_init init;
 }}}
 to see if it is still valid and the state is:
 {{{
 (gdb) p /x init
 $2 = {
   _M_key = 0x13010001,
   _M_init = 0x1
 }
 }}}
 However the static destructor has run and the POSIX key has been deleted.
 This results in `std::terminate()` being called.

 The code for the destructor on ARM is:
 {{{
 006562e0 <__eh_globals_init::~__eh_globals_init()>:
   6562e0:       7903            ldrb    r3, [r0, #4]
   6562e2:       b510            push    {r4, lr}
   6562e4:       4604            mov     r4, r0
   6562e6:       b90b            cbnz    r3, 6562ec
 <__eh_globals_init::~__eh_globals_init()+0xc>
   6562e8:       4620            mov     r0, r4
   6562ea:       bd10            pop     {r4, pc}
   6562ec:       6800            ldr     r0, [r0, #0]
   6562ee:       f04d fe6b       bl      6a3fc8 <pthread_key_delete>
   6562f2:       4620            mov     r0, r4
   6562f4:       bd10            pop     {r4, pc}
 }}}
 and for `aarch64` it is:
 {{{
 0000000010222c30 <__eh_globals_init::~__eh_globals_init()>:
     10222c30:   39401001        ldrb    w1, [x0, #4]
     10222c34:   35000041        cbnz    w1, 10222c3c
 <__eh_globals_init::~__eh_globals_init()+0xc>
     10222c38:   d65f03c0        ret
     10222c3c:   a9bf7bfd        stp     x29, x30, [sp, #-16]!
     10222c40:   910003fd        mov     x29, sp
   return pthread_key_delete (__key);
     10222c44:   b9400000        ldr     w0, [x0]
     10222c48:   94008806        bl      10244c60 <pthread_key_delete>
     10222c4c:   a8c17bfd        ldp     x29, x30, [sp], #16
     10222c50:   d65f03c0        ret
 }}}
 The `_M_init` boolean is not set to `false`.

--
Ticket URL: <http://devel.rtems.org/ticket/4661>
RTEMS Project <http://www.rtems.org/>
RTEMS Project