Re: -Wparentheses lumps too much together

["James K. Lowden" <jklowden at freetds dot org>]

Ian Lance Taylor wrote:
> I have no objection to splitting -Wparentheses into separate warnings
> controlled by separate options.

Thank you, Ian.  

> > which yields (as you know) advice to parenthesize the two && pairs.  
> 
> That particular warning happened to find dozens of real errors when I
> ran it over a large code base.  It may be noise for you, but I know
> from personal experience that it is very useful.

I would like to hear more about that, if you wouldn't mind.  I'm really
quite surprised.  Honestly.  

I don't claim to be the last arbiter in good taste.  It sounds like you're
saying that this warning, when applied to code of uncertain quality,
turned up errors -- cases when the code didn't reflect (what must have
been) the programmer's intentions.  My untested (and consequently firmly
held) hypothesis is that 

1) most combinations of && and || don't need parentheses because 

	(a && b) || (c && d) 

is by far more common than

	a && (b || c) && d

and, moreover, broken code fails at runtime, and  

2) Most programmers know (because they need to know) that && comes before
||.  

I'm sure a few years spent working with the GCC and fielding questions
about it would lower my opinion of the average programmer, so I won't try
to convince you.  But I would like to know more about what you found,
because that's at least objective evidence.  I was unable to find any
metrics supporting the inclusion of this particular warning in -Wall.  

I would hold to this, though: the warnings about precedence are of a
different order than warnings about nesting.  I suggest that well vetted
code doesn't benefit from the kind of false positives that -Wparentheses
can generate.  

I very much appreciate your time and effort.  

Kind regards, 

--jkl