Allow --with-extra-cxxflags to work with HotSpot.

[Volker Simonis]

Hi Ian,

as David already pointed out, the hotspot build is currently being
converted to the configure-based build anyway. You can already test it
by cloning http://hg.openjdk.java.net/build-infra/jdk9 and configuring
with "--enable-new-hotspot-build" ("--disable-new-hotspot-build" is
still the default). The new build is still in a very early stage
(currently only the 'product' build is working) but it should give you
an idea of how it will work. Actually you should get
"--with-extra-cxxflags" for free in the new build system also I'm not
sure it already works (and haven’t tested it yet).

Currently the work on the new build system got a little stuck because
of holidays but as far as I know the plan is still to bring this into
jdk9. If you have any suggestions for improvements the build-infra
repo and mailing list are definitive the way to go. And if you have
some good patches against build-infra I can try to help and sponsor
them.

Regards,
Volker


On Wed, Jul 22, 2015 at 1:20 AM, David Holmes <david.holmes at oracle.com> wrote:
> Hi Ian,
>
> On 22/07/2015 3:01 AM, Ian Rogers wrote:
>>
>> The following (modest) patch against jdk9dev allows the top-level
>> configure
>> with --with-extra-cxxflags to pass options to the HotSpot build. An
>> example
>> would be:
>>
>> configure --fastdebug --with-extra-cxxflags=-std=c++11
>>
>> Unless --with-extra-cxxflags is specified the option has no effect. I'd
>> like to work to get this merged into jdk9dev and would appreciate any
>> help.
>
>
> Unfortunately this is not quite as simple as it appears due to the mess in
> the hotspot build system regarding flags usage. Once upon a time we had
> CFLAGS and CPPFLAGS but there was confusion whether CPP meant C++ or
> C-pre-processor. It actually meant the latter but was mistakenly thought to
> be the former (g++ args versus gcc args) and was eventually renamed to
> CXXFLAGS. This results in quite a mess because we have eg:
>
> ./linux/makefiles/rules.make:CC_COMPILE = $(CC) $(CXXFLAGS) $(CFLAGS)
> ./linux/makefiles/rules.make:CXX_COMPILE      = $(CXX) $(CXXFLAGS) $(CFLAGS)
>
> which combines the "C" flags (which were always intended to just be the
> compiler flags, which was a combined C/C++ compiler anyway) and the (now)
> C++ flags (most of which are not at all C++ specific). So it will get the
> EXTRA_CFLAGS and the EXTRA_CXXFLAGS on each compilation.
>
> Then things get worse because hotspot uses both sets of flags but the JDK
> uses CXXFLAGS as the primary compiler flags. So taking cross-compilation as
> an example, we set EXTRA_CFLAGS to hold the cross-compiler flags used in
> hotspot, and set EXTRA_CXXFLAGS to hold the cross-compiler flags for the JDK
> build. So with your proposed change we will now get the cross-compiler flags
> specified twice on each command-line in the hotspot build. Whether that is
> harmful I don't know - I'm just pointing out that this is far from clear cut
> and would need some resources to establish that the change is indeed safe.
>
> This should all be resolved once the hotspot build is converted to be a full
> configure-based build. And because that is in the pipeline we avoid doing
> any major surgery to the (fragile) hotspot build system.
>
> David
> -----
>
>
>
>> Thanks,
>> Ian Rogers, Google.
>>
>> ---
>> Allow --with-extra-cxxflags to work with HotSpot.
>>
>> Pass down EXTRA_CXXFLAGS from gnumake's invocation or environment.
>>
>> diff -r fff6b54e9770 make/aix/makefiles/vm.make
>> --- a/make/aix/makefiles/vm.make        Thu Jul 16 19:28:37 2015 -0700
>> +++ b/make/aix/makefiles/vm.make        Tue Jul 21 08:55:08 2015 -0700
>> @@ -112,6 +112,7 @@
>>   # Extra flags from gnumake's invocation or environment
>>   CFLAGS += $(EXTRA_CFLAGS)
>>   LFLAGS += $(EXTRA_CFLAGS)
>> +CXXFLAGS += $(EXTRA_CXXFLAGS)
>>
>>   # Don't set excutable bit on stack segment
>>   # the same could be done by separate execstack command
>> diff -r fff6b54e9770 make/bsd/makefiles/vm.make
>> --- a/make/bsd/makefiles/vm.make        Thu Jul 16 19:28:37 2015 -0700
>> +++ b/make/bsd/makefiles/vm.make        Tue Jul 21 08:55:08 2015 -0700
>> @@ -114,6 +114,7 @@
>>   # Extra flags from gnumake's invocation or environment
>>   CFLAGS += $(EXTRA_CFLAGS)
>>   LFLAGS += $(EXTRA_CFLAGS)
>> +CXXFLAGS += $(EXTRA_CXXFLAGS)
>>
>>   # Don't set excutable bit on stack segment
>>   # the same could be done by separate execstack command
>> diff -r fff6b54e9770 make/linux/makefiles/vm.make
>> --- a/make/linux/makefiles/vm.make      Thu Jul 16 19:28:37 2015 -0700
>> +++ b/make/linux/makefiles/vm.make      Tue Jul 21 08:55:08 2015 -0700
>> @@ -117,6 +117,7 @@
>>   # Extra flags from gnumake's invocation or environment
>>   CFLAGS += $(EXTRA_CFLAGS)
>>   LFLAGS += $(EXTRA_CFLAGS)
>> +CXXFLAGS += $(EXTRA_CXXFLAGS)
>>
>>   # Don't set excutable bit on stack segment
>>   # the same could be done by separate execstack command
>> diff -r fff6b54e9770 make/solaris/makefiles/vm.make
>> --- a/make/solaris/makefiles/vm.make    Thu Jul 16 19:28:37 2015 -0700
>> +++ b/make/solaris/makefiles/vm.make    Tue Jul 21 08:55:08 2015 -0700
>> @@ -110,6 +110,7 @@
>>
>>   # Extra flags from gnumake's invocation or environment
>>   CFLAGS += $(EXTRA_CFLAGS)
>> +CXXFLAGS += $(EXTRA_CXXFLAGS)
>>
>>   # Math Library (libm.so), do not use -lm.
>>   #    There might be two versions of libm.so on the build system:
>>
>