Re: macro directives inside macro arguments undefined

[Steven Bellovin <smb%cs.columbia.edu@localhost>]

On Feb 24, 2011, at 9:32 14AM, David Laight wrote:

> On Thu, Feb 24, 2011 at 11:31:35AM +0000, Iain Hibbert wrote:
> 
> The original code seems to be:
> 
>>              sprintf(t,
>> #ifdef       USE_QUAD_T
>> #ifdef       PRId64
>>                      " Forward: Pkts in %" PRId64 " Bytes in %" PRId64
>>                      " Pkts out %" PRId64 " Bytes out %" PRId64
>>                      " Backward: Pkts in %" PRId64 " Bytes in %" PRId64
>>                      " Pkts out %" PRId64 " Bytes out %" PRId64,
>> #else
>>                      " Forward: Pkts in %qd Bytes in %qd Pkts out %qd Bytes 
>> out %qd Backward: Pkts in %qd Bytes in %qd Pkts out %qd Bytes out %qd",
>> #endif /* PRId64 */
>> #else
>>                      " Forward: Pkts in %ld Bytes in %ld Pkts out %ld Bytes 
>> out %ld Backward: Pkts in %ld Bytes in %ld Pkts out %ld Bytes out %ld",
>> #endif
>>                      sl->isl_pkts[0], sl->isl_bytes[0],
>>                      sl->isl_pkts[1], sl->isl_bytes[1],
>>                      sl->isl_pkts[2], sl->isl_bytes[2],
>>                      sl->isl_pkts[3], sl->isl_bytes[3]);
>> 
>>              t += strlen(t);
> 
> That is just trully horrid and should be converted to snprintf().
> The chance of the buffer being big enough seesm unlikely to be
> guaranteeable!
> 
Why do you say that?  We're only dealing with numbers here (rather than %s); 
their length is bounded by the machine's word size.
> 


                --Steve Bellovin, http://www.cs.columbia.edu/~smb