Platform dependent flag adjustments

[David Holmes]

On 18/10/2012 3:47 AM, Vladimir Kozlov wrote:
> We usually do flags adjustment for platforms in vm_version_<arc>.cpp
> files. VM_Version_init() is called after Arguments::parse(args).

Yes - but it is unfortunate in that VM_Version::initialize() method is 
not the obvious place to do such things, but it is a platform specific 
initialization hook that is invoked at near-enough the right time. That 
said, it all depends on what these flags do as to whether tweaking them 
in VM_Version::initialize() is too late, as a lot of other 
initialization has happened by then.

Further if these are really OS specific rather than arch specific flags 
then VM_Version::initialize() may not be the right place at all, in 
which case os::init2(), as Harold mentioned, may be a better choice.

There's no nice neat simple solution here. Ultimately you may need a 
per-arch and per-OS hook per-flag, and even then you might also need 
pre- and post- variants to get the order right! So what we have is quite 
ad-hoc and often just implemented in the most convenient way at the time.

David
-----


> Vladimir
>
> Volker Simonis wrote:
>> Hi,
>>
>> for our PowerPC/AIX port I'm currently looking for a place where I can
>> do platform dependent adjustments to command line arguments which are
>> available on special platforms only.
>>
>> For our private ports, we did all these adjustments conditionally in
>> 'parse_each_vm_init_arg()' and I noticed that the original version of
>> this method already contains platforms specific parts (e.g.
>> SOLARIS_ONLY(..)). But these solution is not very attractive because
>> it clutters shared code. It also seems unintuitive to handle platform
>> dependent flags which are declared in special platform dependent files
>> (e.g. src/cpu/<arch>/vm/globals_<arch>.hpp:) in a central shared
>> method. Finally the current solution will scale poorly with new
>> platform ports coming into the OpenJDK.
>>
>> I also noticed that the the 'Arguments' class declares a static method
>> 'do_pd_flag_adjustments()'. Unfortunately this method is never defined
>> nor called. I saw that this method was there from the initial checkin
>> and I'm wondering if this was a first attempt to generalize the flag
>> adjustment?
>>
>> Or perhaps there's an even better way to do platform dependent flag
>> adjustments which I've just missed?
>>
>> Any insights and hints are highly welcome.
>>
>> Regards,
>> Volker