fix hotspot build failures with -D_FORTIFY_SOURCE=2 and -Wformat=1

[Andrew Haley]

Kelly O'Hair wrote:
> The issue seems so simple to me.
> If the function return is to be ignored, you make an explicit cast
> to void. This practice is so old and common I don't understand why
> it's so complicated.

> gcc/g++ are not the only compilers on the planet.
> Writing portable C or C++ code becomes increasingly more complicated
> when you have to rely on special features of the compiler to get them
> to shut up about perfectly valid code.
> 
> What happened to following the standards?
> 
> WG14/N1124 6.3.2.2 void
> 
> "... If an expression of any other type is evaluated as a void
> expression, its value or designator is discarded.
> (A void expression is evaluated for its side effects.)"

Huh?  The standard doesn't say that you should not warn about
legal but potentially problematic code.  That's what most
warnings are, after all.

Andrew.