[PATCH] [C] Warn when calculating abs(unsigned_value)

[Joseph Myers]

On Wed, 15 Aug 2018, Martin Sebor wrote:

> Detecting some of these bugs without too much noise would require
> moving the warning out of the front-end and to some later point
> after VRP has run.

But you need the information about whether the conversion was explicit or 
implicit.  If someone does

abs ((int) unsigned_var)

it's presumably intentional and should not receive a warning.  If they do

abs (unsigned_var)

it's suspect.  If they do

abs (long_var)

it's entirely possible they know the long value is within range for int, 
but it came from some API that produces long.

-- 
Joseph S. Myers
joseph@codesourcery.com