bizarre warnings

[Zachary Alexander Weinberg]

While trying to make some code compile cleanly with -W -Wall I got some
warnings I've never seen before.

t-coverage/string-test.inc:314: warning: unsigned value < 0 is always 0
t-coverage/string-test.inc:346: warning: unsigned value >= 0 is always 1

These are valid from the compiler's point of view, but the code is correct
(it's testing corner cases in a complicated macro).  Is there a
-Wno-something switch that kills these and *only* these warnings?

t-coverage/libm-test.inc:2382: warning: overflow on truncation to integer
t-coverage/libm-test.inc:6212: warning:  ediv invalid operation error

These aren't anywhere in the docs that I can find.  The first one appears
on a line with no integer values in it anywhere.  The second appears on
the closing } of a function; there's no `ediv' anywhere in the program.
Both appear only when inlining is on.

Also, for reference, is there any switch that turns off -W?

zw