[Bug c++/20316] New: attribute((packed)) and call by reference

[nkoch at demig dot de]

I have this test program:

struct P { char a; int b; } __attribute__ ((__packed__));

int f (char & i) { return ++ i; }
int f (int  & i) { return ++ i; }
int f (char * i) { return ++ * i; }
int f (int  * i) { return ++ * i; }

int main ()
{
  P x;
  x.a = 1;
  x.b = 1;
  int i = f (x.a) + f (x.b) + f (& x.a) + f (& x.b);
  return 0;
}


It compiles with gcc3.3 (gcc version 3.3.6 20050223 (prerelease) [FreeBSD])
but not with gcc.3.4 (gcc version 3.4.4 20050211 (prerelease) [FreeBSD]).

GCC reports:
test.cpp: In function `int main()':
test.cpp:13: error: cannot bind packed field `x.P::a' to `char&'
test.cpp:13: error: cannot bind packed field `x.P::b' to `int&'

Probably, this is not a bug but a feature, but what can I do
to my program, which needs a lot of packed structures and runs fine
with gcc3.3?
Perhaps I have to cast away the packed attribute somehow ??
I understand, that my code may not work on cpus needing some specific
alignment, but where is the problem with char? And if this is a cpu issue,
why do the pointers work, but _not_ the references?

-- 
           Summary: attribute((packed)) and call by reference
           Product: gcc
           Version: 3.4.4
            Status: UNCONFIRMED
          Severity: normal
          Priority: P2
         Component: c++
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: nkoch at demig dot de
                CC: gcc-bugs at gcc dot gnu dot org
 GCC build triplet: i386-portbld-freebsd4.10
  GCC host triplet: i386-portbld-freebsd4.10
GCC target triplet: i386-portbld-freebsd4.10


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=20316