[cfe-commits] [Patch] Add new warning for logical not on LHS of comparison

Richard Trieu rtrieu at google.com
Fri Oct 12 09:38:29 PDT 2012

This patch is for a new warning to Clang, called -Wlogical-not-compare.  It
is designed to catch the case where the user is attempting to negate a
comparison, but only manages to negate the LHS because of missing parens.
 For instance, warn here:

     if (!x < 5)

The user probably meant:

     if (!(x < 5))


     if (x >= 5)

When emitted, the warning will have a note suggesting this as a fix-it
(drop the not and inverting the comparison operator).

Also, a second note will be offer parenthesis around the LHS to silence
this warning.

     if ((!x) < 5)

This will not warn.
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