[PATCH] (Title Corrected) Build fails to compile jchuff.c using gcc 4.8.5 on zLinux

[Erik Joelsson]

Hello Adam,

When adding a disabled warning like this, we need to also add a clear 
comment describing why it's necessary. In this case it's caused by a bug 
in GCC and only affects certain versions. Otherwise, we will likely try 
to remove them later and without information on why it was added, we 
will just conclude that the warning is not triggering with the official 
GCC version and remove it.

If the affected versions is limited, then we may also consider making 
this conditional on the GCC version. The version is available in the 
variables TOOLCHAIN_VERSION, CC_VERSION_NUMBER and CXX_VERSION_NUMBER.

/Erik

On 2018-01-18 03:15, Adam Farley8 wrote:
> Hi All
>
> I sent an email to the 2d-dev list yesterday, but I'll respond here as 
> well
> so you guys know I'm not ignoring you. :)
>
> > This is all correct, thanks David!
> >
> > For the official toolchains (basically what Oracle builds with), we very
> > much like to keep warnings-as-errors active, because it's a very
> > valuable tool in keeping the code healthy. For other toolchains, it
> > depends, as David says.
> >
> > We have a mechanism for disabling warnings for specific toolchain types
> > (gcc, clang, solstudio, visualstudio) on a per library basis. We also
> > have the ability to add flags globally for specific toolchain versions
> > in configure, in flags.m4. If we want to solve this by disabling a
> > warning due to a bug in a specific gcc version, I would recommend the
> > latter.
> >
> > /Erik
>
> This is correct. In flags.m4, GCC has a potential
> DISABLE_WARNING_PREFIX value of "-Wno-".
>
> Yesterday I posted to 2d-dev and recommended changing
> Awt2dLibraries.gmk, which supplies suffixes for that prefix
>
> Basically you change line 494 to this:
>
>     DISABLED_WARNINGS_gcc := clobbered array-bounds, \
>
> This puts a -Wno-array-bounds on the gcc compile command for
> jchuff.c, thereby ignoring the error-warning I'm seeing.
>
> I ran a build to confirm this works. It did, and the build completed
> without further errors.
>
> This fix, if accepted, means --disable-warnings-as-errors will not be 
> needed
> in future zLinux compiles using this gcc (which, as David points out, 
> is the
> gcc version on the build list).
>
> Just "bash ./compile" and "make all". Simples!
>
> Please send future responses through my email to the 2d-dev list.
>
> http://mail.openjdk.java.net/pipermail/2d-dev/2018-January/008836.html
>
> Thanks for your time. :)
>
> Best Regards
>
> Adam Farley
>
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