RFR: 8030350: Enable additional compiler warnings for GCC

[Lois Foltan]

Hi Mike,

We need to be careful that these options are also supported on MacOS 
with the clang compiler in case there is a future migration to clang for 
JDK 9 or higher.

Thanks,
Lois

On 12/17/2013 7:08 PM, Mike Duigou wrote:
> Hello all;
>
> This is a change which enables additional compiler warnings for native compilation when using GCC. The (-Wformat -Wformat-security) options are supported by GCC 3.0.4 (the earliest version I checked, c. February 2002) and later so we shouldn't see issues with incompatibility.- Wextra appears to have been added in GCC 3.4.X line (c. 2004) so it should also be reasonably well adopted and replaces -W.
>
> The core of the change is to add :
>
> -Wextra -Wno-unused-parameter -Wformat -Wformat-security
>
> for general C and CC++ compilations. For HotSpot C++ compiles a slightly less aggressive set is used:
>
> -Wformat -Wformat-security
>
> is used.
>
> Webrev here:
>
> http://cr.openjdk.java.net/~mduigou/JDK-8030350/0/webrev/
>
> For the curious, yes, the additional checks do generate additional warnings. ;-)
>
> This change is targeted at the JDK 9 repos but could be backported to JDK 8 fairly easily/safely.
>
> Mike
>