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

[Coleen Phillimore]

Are there pragmas in gcc to disable selected warning messages like there 
are in the windows Visual C++ and as far as I can remember, the EDG 
front ends?  An implementation is free to warn about whatever it wants 
but generally provides pragmas or command line options to disable 
certain warnings.  It's better than turning them all off or remembering 
to write silly code to satisfy a certain compiler.

Coleen

David Holmes - Sun Microsystems wrote:
> I don't know who is most at fault here: the glibc folk for marking 
> these methods with an attribute that forces a warning to always be 
> issued regardless of what the developer writes in his code, or selects 
> for her compiler options; or the gcc folk for providing such an 
> attribute in the first place. :-( Too much hand-holding if you ask me.
>
> But having to store into an unused local to get around this is plain 
> absurd!
>
> David Holmes
>
> Kelly O'Hair said the following on 12/05/08 07:42:
>> It's a quality of the compiler implementation issue.
>> I know there are no formal standard violations here, but the
>> intent of an explicit void cast has always been clear.
>>
>> -kto
>>
>> Andrew Haley wrote:
>>> Kelly O'Hair wrote:
>>>> Both fwrite() and (void)fwrite() are legal,
>>>> the first one is a potential error, but the later
>>>> is defined by the standard as having the function return value
>>>> explicitly "discarded".
>>>
>>> The standard doesn't distinguish between them.  Both are evaluated
>>> as void expressions.
>>>
>>>> So warning about a value that has been explicitly "discarded" by
>>>> the terms of the standard seems like a very questionable warning.
>>>
>>> Perhaps so, but that is nothing to do with standards conformance,
>>> which you were questioning.  Let me be clear: a C compiler is allowed
>>> to warn about anything at all, as long as every standard program is
>>> executed according to the rules of the abstract machine.
>>>
>>> Andrew.
>>>
>>>
>>>> Andrew Haley wrote:
>>>>> 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.
>>>