All built-in memory allocations functions are missing the aligned_alloc attribute.  As the output of the test case below shows, the absence of the attribute on aligned_alloc and realloc causes __builtin_object_size to fail to determine the size of objects they allocate.

$ cat a.c && gcc -O2 -S -Wall -Wextra -Wpedantic -fdump-tree-optimized=/dev/stdout a.c | grep -e ^test -eabort
void sink (void*);

unsigned size (unsigned n)
{
  return n;
}

void test_aligned_alloc (unsigned a)
{
  unsigned n = size (7);

  void *p = __builtin_aligned_alloc (n, a);
  if (__builtin_object_size (p, 0) != n)
    __builtin_abort ();
  sink (p);
}

void test_alloca (void)
{
  unsigned n = size (13);
 
 void *p = __builtin_alloca (n);
  if (__builtin_object_size (p, 0) != n)
    __builtin_abort ();
  sink (p);
}

void test_calloc (void)
{
  unsigned m = size (19);
  unsigned n = size (23);

  void *p = __builtin_calloc (m, n);
  if (__builtin_object_size (p, 0) != m * n)
    __builtin_abort ();
  sink (p);
}

void test_malloc (void)
{
  unsigned n = size (17);

  void *p = __builtin_malloc (n);
  if (__builtin_object_size (p, 0) != n)
    __builtin_abort ();
  sink (p);
}

void test_realloc (void *p)
{
  unsigned n = size (31);

  p = __builtin_realloc (p, n);
  if (__builtin_object_size (p, 0) != n)
    __builtin_abort ();
  sink (p);
}
test_aligned_alloc (unsigned int a)
  __builtin_abort ();
test_alloca ()
test_calloc ()
test_malloc ()
test_realloc (void * p)
  __builtin_abort ();