Sebastian Redl wrote:
> Balogh, Ray wrote:
>> Dear GCC folks:
>>
>> I'm having a problem with GCC 2.95.3 that appears to be a compiler
>> bug. It seems to be optimizing out inlined function code with side
>> effects, and is related to binding a non-const pointer to a const
>> pointer reference function parameter. The problem only happens with
>> optimization on, and goes away with -O0.
>>
>> inline unsigned unpack2 (const byte *&data)
>> {
>> unsigned val = data[0] << 8 | data[1];
>> data += 2;
>> return val;
>> }
>> inline unsigned unpack2 (const byte *&data, unsigned &count)
>> {
>> unsigned val = data[0] << 8 | data[1];
>> data += 2;
>> count -= 2;
>> return val;
>> }
>>
>> void extractInfo (byte *&data, unsigned &datalen,
>> unsigned &f1, unsigned &f2)
>> {
>> cout << "data = " << data << ", datalen = " << datalen << endl;
>> f1 = unpack2 (data, datalen);
>> cout << "data = " << data << ", datalen = " << datalen << endl;
>>
>> byte *peek = data;
>> //const byte *peek = data; // **** Adding "const" works around
>> the compiler problem ****
>> // Another work-around is to uncomment
>> the non-const f1 of unpack2() above
>>
>> unsigned tmp = datalen;
>> cout << "peek = " << peek << ", tmp = " << tmp << endl;
>> (void) unpack2 (peek, tmp); // skip over irrelevant field
>> cout << "peek = " << peek << ", tmp = " << tmp << endl;
>> (void) unpack2 (peek, tmp); // skip over irrelevant field
>> cout << "peek = " << peek << ", tmp = " << tmp << endl;
>>
>> unsigned xlen = unpack2 (peek, tmp);
>> cout << "peek = " << peek << ", tmp = " << tmp << endl;
>>
>> f2 = xlen;
>> }
>>
> In my opinion, the bug is that this even compiles. It's invalid to write
> char *pc;
> const char **ppc = &pc;
>
> Why should it be valid to write
> char *pc;
> const char *&rpc = pc;
>
I agree. The code is invalid; modern g++ generates an error.
Andrew.
