RFR(S): 8141290: AIX: fix build after '8140661: Rename LDFLAGS_SUFFIX to LIBS'

[Volker Simonis]

On Tue, Nov 3, 2015 at 6:20 PM, Magnus Ihse Bursie
<magnus.ihse.bursie at oracle.com> wrote:
> On 2015-11-03 17:20, Volker Simonis wrote:
>>
>> Hi,
>>
>> unfortunately, change '8140661: Rename LDFLAGS_SUFFIX to LIBS' broke
>> the AIX build.
>
>
> I'm sorry for that. :-(
>>
>>
>> Can somebody please review this small change which fixes the build?
>>
>> http://cr.openjdk.java.net/~simonis/webrevs/2015/8141290/
>> https://bugs.openjdk.java.net/browse/JDK-8141290
>
>
> The fix looks good to me. However, just to be sure, I've put it to a spin on
> JPRT, so it does not break any other platforms. I'll let you know the
> results when I have them.
>
>>
>>
>> Besides this immediate build fix I have some general questions/remarks
>> regarding change '8140661: Rename LDFLAGS_SUFFIX to LIBS':
>>
>> First of all I think it is always good to further cleanup and simplify
>> the build and the idea to separate linker options from library
>> dependencies is yet another good step into this direction.
>
> Thanks. :)
>
>>
>> But I have some problems understanding the semantics of the new
>> JDKLIB_LIBS variable. As far as I understand it, JDKLIB_LIBS holds the
>> native library dependencies for the native libraries build within the
>> jdk build (is this true?). As such I'd expect that every call to
>> SetupNativeCompilation in jdk/make/lib/ should contain a line like
>> "LIBS := $(JDKLIB_LIBS)". If that would have been true, we wouldn't
>> have seen any problems on AIX.
>>
>> Before change 8140661, LDFLAGS_JDKLIB contained the library dependency
>> "-liconv" and because every call to SetupNativeCompilation in
>> jdk/make/lib/ contained a line like "LDFLAGS := $(LDFLAGS_JDKLIB)" the
>> dependency to libiconv.so was always satisfied. Now I admit, that
>> having "-liconv" in the LDFLAGS is probably not very elegant and it is
>> probably also not strictly needed, because potentially not every
>> native jdk library really depends on libiconv.so. So in general the
>> cleanup done by 8140661 is good (if it is done right :)
>>
>> But until now, not every call to SetupNativeCompilation contains the
>> line "LIBS := $(JDKLIB_LIBS)". Instead, a lot of the calls still
>> contain lines like "LIBS_unix := -ljava" although JDKLIB_LIBS already
>> contains "-ljava -ljvm" by default on all Unix platforms. Also, there
>> are a lot of lines like "LIBS_solaris := -lc" although JDKLIB_LIBS
>> already contains "-lc" by default on Solaris.
>>
>> So my question: are there plans to further improve the build system by
>> adding "LIBS := $(JDKLIB_LIBS)" to all the calls to
>> SetupNativeCompilation in jdk/make/lib/ and remove the then redundant
>> platform specific settings?
>
>
> Yes, the plan is to continue cleaning up how this is handled. Let me start
> with some background here:
>
> The new build-infra based hotspot build system has a more or less working
> prototype. The next step is to integrate this properly in the build-infra
> family. For this to work, we need to re-think some of the assumptions in
> build-infra, mostly relating to how we handle flags. Right now, we have not
> really been clear on what flags are needed where, and why. For instance,
> -shared is needed to compile shared libraries on gcc, and should really
> belong in SetupNativeCompilation, but is now set as a part of the JDK flags.
>
> So the whole area of flags needs an overhaul. My general idea is to break
> the flags into separate units, somewhat like FREETYPE_LIBS and
> FREETYPE_CFLAGS, so you only need to add the flags you actually need for
> every library. (Maybe increase the abstraction so you just need to declare a
> dependency on freetype to get both FREETYPE_LIBS and FREETYPE_CFLAGS
> automatically?) But the whole project is of the kind where you have to start
> clean up the mess and then see where it lands.
>
> As for JDKLIB_LIBS, I'm not really sure of the semantics myself. :-) As you
> say, it is included in most libs, but not all, but the contents are still
> duplicated in some places. I think it should just go away. Or maybe be split
> up in a "i need libjava/libjvm" (-ljava -ljvm) and "really, all libraries
> need this" (-lc on solaris). And make sure that all libraries really get the
> "really, all libraries need this" part.
>

Thanks for the detailed explanation. I see the build system is on a good way :)

Regarding JDKLIB_LIBS I think we should try to minimize duplication
and redundancy.
So if we need libjava/libjvm for all libraries anyway it would be good
to have it in JDKLIB_LIBS and get rid of all the extra "-ljvm -ljava"
options in every call to SetupNativeCompilation. The same holds true
for "-lc" on Solaris. But for this to work, we of course need to have
LIBS := $(JDKLIB_LIBS) in every call to SetupNativecompilation first.

>> I think that would be yet another nice
>> cleanup and in that case I'd also prefer to remove '-liconv' from
>> JDKLIB_LIBS on AIX and only add it to the required libraries, in the
>> same way as this is done for MacOS X.
>
>
> That's something I think you can do already. :-) If it's just a few
> libraries that need -liconv, I'd suggest using LIBS_aix for those. If it's
> like almost every library, you should probably wait a while and see where
> the library handling ends up.

I agree - I'm just fixing it the right way now. The downside of this
will be that I'll need you as sponsor because it requires the
re-generation of the configure script because of the changes in
flags.m4 :)

>
> /Magnus
>