[Bug lto/51255] New: Using -flto breaks code which puts values in .ctors or .init_array

[ian at airs dot com]

http://gcc.gnu.org/bugzilla/show_bug.cgi?id=51255

             Bug #: 51255
           Summary: Using -flto breaks code which puts values in .ctors or
                    .init_array
    Classification: Unclassified
           Product: gcc
           Version: 4.7.0
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: lto
        AssignedTo: unassigned@gcc.gnu.org
        ReportedBy: ian@airs.com


A test case similar to this is used by the gcc configure script
(HAVE_INITFINI_ARRAY in gcc/acinclude.m4):


extern void abort ();
static int count;

static void
init1005 ()
{
  if (count != 0)
    abort ();
  count = 1005;
}
void (*const init_array1005[]) ()
  __attribute__ ((section (".init_array.01005"), aligned (sizeof (void *))))
  = { init1005 };
static void
fini1005 ()
{
  if (count != 1005)
    abort ();
}
void (*const fini_array1005[]) ()
  __attribute__ ((section (".fini_array.01005"), aligned (sizeof (void *))))
  = { fini1005 };

static void
ctor1007 ()
{
  if (count != 1005)
    abort ();
  count = 1007;
}
void (*const ctors1007[]) ()
  __attribute__ ((section (".ctors.64528"), aligned (sizeof (void *))))
  = { ctor1007 };
static void
dtor1007 ()
{
  if (count != 1007)
    abort ();
  count = 1005;
}
void (*const dtors1007[]) ()
  __attribute__ ((section (".dtors.64528"), aligned (sizeof (void *))))
  = { dtor1007 };

static void
init65530 ()
{
  if (count != 1007)
    abort ();
  count = 65530;
}
void (*const init_array65530[]) ()
  __attribute__ ((section (".init_array.65530"), aligned (sizeof (void *))))
  = { init65530 };
static void
fini65530 ()
{
  if (count != 65530)
    abort ();
  count = 1007;
}
void (*const fini_array65530[]) ()
  __attribute__ ((section (".fini_array.65530"), aligned (sizeof (void *))))
  = { fini65530 };

static void
ctor65535 ()
{
  if (count != 65530)
    abort ();
  count = 65535;
}
void (*const ctors65535[]) ()
  __attribute__ ((section (".ctors"), aligned (sizeof (void *))))
  = { ctor65535 };
static void
dtor65535 ()
{
  if (count != 65535)
    abort ();
  count = 65530;
}
void (*const dtors65535[]) ()
  __attribute__ ((section (".dtors"), aligned (sizeof (void *))))
  = { dtor65535 };

int
main ()
{
  if (count != 65535)
    abort ();
  return 0;
}

When using a recent version of GNU ld or gold, this program is intended to
compile and run correctly.  However, if compiled with "-flto -O", it fails,
even using a recent linker.  It fails because the LTO pass does not realize
that the functions in the .ctors and .init_array sections are going to be run
before main.