[Bug c/42103] New: [4.4 regression] packed 64-bit field reports as violation of strict aliasing rules

[tlesher at digium dot com]

The following two declarations work under gcc 4.2.4, but are inconsistent under
gcc 4.4.1:

static inline void put_unaligned_uint64(void *p, uint64_t datum)
{
    struct { uint64_t d; } __attribute__((packed)) *pp = p;
    pp->d = datum;
}

static inline void put_unaligned_uint32(void *p, unsigned int datum)
{
    struct { unsigned int d; } __attribute__((packed)) *pp = p;
    pp->d = datum;
}

Given that the only difference between these two functions is that one is
64-bit, while the other is 32-bit, they should either both fail under strict
aliasing rules or they should both succeed with no error.  The error reported
under gcc 4.4.1 is as follows:
/home/tilghman/Asterisk/asterisk-trunk/include/asterisk/unaligned.h:55: error:
dereferencing pointer ‘pp’ does break strict-aliasing rules
/home/tilghman/Asterisk/asterisk-trunk/include/asterisk/unaligned.h:53: note:
initialized from here


-- 
           Summary: [4.4 regression] packed 64-bit field reports as
                    violation of strict aliasing rules
           Product: gcc
           Version: 4.4.1
            Status: UNCONFIRMED
          Severity: normal
          Priority: P3
         Component: c
        AssignedTo: unassigned at gcc dot gnu dot org
        ReportedBy: tlesher at digium dot com
  GCC host triplet: x86_64-linux-gnu
GCC target triplet: x86_64-linux-gnu


http://gcc.gnu.org/bugzilla/show_bug.cgi?id=42103