compile with gcc option -O0 or -O

[David Brown]

On 16/09/2011 12:05, Miles Bader wrote:
> David Brown<david@westcontrol.com>  writes:
>>> ... but be a bit wary of any warning option which isn't included in
>>> -Wall or -Wextra -- they're usually omitted for a reason (typically
>>> because they yield tons of false positives on reasonable code).
>>
>> That depends on your definition of "reasonable code" !
>
> Of course.  :)
>
> In general, though, there is some thought behind what's included in
> -Wall/-Extra.  Stuff that's omitted tends to be where the warnings are
> domain-specific, reflect programming practices which aren't widespread
> enough, or where the gcc implementation is simply lacking in some
> obvious way (sometimes it's very tricky to get the heuristics right).
>

Absolutely true, of course.

gcc is designed to support a huge range of code and coding practices - 
with that range covering different application areas, different 
programmer experiences and abilities, different code quality 
requirements, different fashions, different code sizes, and different 
times.  It has to work well for amateur code written 20 years ago and 
aeroplane-quality code written to modern standards.  So the -Wall and 
-Wextra groups are picked to give a reasonable compromise, and the 
individual flags are there for people who want more control.

> -Wpadded, for instance, may be very interesting for embedded devs, but
> probably not so much for many others, and yields vast quantities of
> warnings on "ordinary" code.
>
> -Wfloat-equal, on the other hand, reflects a rule of thumb which is very
> useful when applied intelligently (i.e., by a human), but is less well
> suited to automatic application.  [Testing for floating-point equality
> is unreliable if the values being tested are the result of calculation,
> but _is_ reliable if the values are the result of simple assignment,
> especially certain values like 0.0 -- and the compiler is very unlikely
> to be able to distinguish these cases.  If you _know_ that your
> code-base never, ever, tests equality in the latter case, you can safely
> use -Wfloat-equal, but this isn't something that can be relied upon.]
>
> <etc etc blah blah>
>
> -miles
>