You are right that the warning is wrong in the case that both are zero, I'm not sure if this is still the case in newer gcc versions since I only tried 4.8.*. I'm okay with keeping my local patch to disable the warning in my case and I can fully understand that adding a not necessary test to remove a false warning would harm performance.
2015-08-20 19:05 GMT+02:00 Scott Robison <scott at casaderobison.com>: > On Thu, Aug 20, 2015 at 10:46 AM, Scott Doctor <scott at scottdoctor.com> > wrote: > > > My opinion is to keep it portable. The warning is there for a reason. you > > are worried about performance yet are calling a function that does > nothing, > > which will take more memory cycles than a simple check for zero. > > > > I didn't say don't make a change. I'm observing there are things to > consider. In particular the optimization strategies that the SQLite team > have pursued for several years now have been *tiny* little optimizations > that would never be justifiable on their own but that really add up, > particularly for small devices probably running on batteries. > > > > Trying to memset a zero length is a bug, not the warning. Add an if > > statement around it. If the variable is local, it will probably be > > optimized as a register variable and a zero check of a register is a > single > > op-code. > > > > Trying to memset a zero length buffer is not a bug if the length of the > sequence of bytes that needs to be set is zero. C89 in particular does not > disallow this use. > > > > the problem with disabling warnings is that even if this instance is not > > an error, some other part of the code may end up with the same situation > > but is an error in the coding. I would prefer code that can be compiled > > with all warnings turned on that gives no warnings than have a potential > > problem because of a glitch in the code. > > > > I don't think anyone called for disabling the warning. I think it should > just be ignored in this case, just as I ignore warnings that are generated > by Visual C++ when I compile SQLite there. > > -- > Scott Robison > _______________________________________________ > sqlite-users mailing list > sqlite-users at mailinglists.sqlite.org > http://mailinglists.sqlite.org/cgi-bin/mailman/listinfo/sqlite-users >
