for (i = 0; i < 4; ++i) { assert( self->magic[i] == JAM_STRING_MAGIC ); assert( self->value[self->capacity + i] == JAM_STRING_MAGIC ); }
static void assert_invariants( string* self ){    assert( self->size < self->capacity );    assert( ( self->capacity <= sizeof(self->opt) ) == ( self->value == self->opt ) );    assert( strlen( self->value ) == self->size );}