Howto re-compile ony parts?

[Igor Nekrestyanov]

Thanks Phil!

I just found similar explanation in the jdk\make\common\Makefile-vers.gmk

#
# Makefile for linking with mapfiles.
#
# NOTE: Not using a mapfile will expose all your extern functions and
#    extern data symbols as part of your interface, so unless your
#    extern names are safe from being mistaken as names from other
#    libraries, you better use a mapfile, or use a unique naming
#    convention on all your extern symbols.
#
# The mapfile will establish versioning by defining the exported interface.
#
# The mapfile can also force certain .o files or elf sections into the
#   the different segments of the resulting library/program image.
#
# The macro FILES_m can contain any number of mapfiles.
#

However, it seems to be used on Linux/Solaris only (everything inside is 
under ifder solaris/linux) and this puzzle me a bit.
So, it seems if name clashing is primary reason we should be protecting 
from this on Windows too.

-igor

Phil Race wrote:
> Igor Nekrestyanov wrote:
>>>>  
>>> Thank you many many times for this, I don't know how long further I
>>> would have searched without this information.
>>> What is this file good for and how is it used during the build?
>>>   
>> I believe mapfiles are used to defines set of methods to be exported 
>> from shared library.
>> Perhaps, you may grep build log file for mapfile name to see how this 
>> is done exactly
>> (do not have linux build here and have not checked log myself).
>>
>> My understanding of why we use this is following.
>> Symbol tables for all methods from the library are large and explicit 
>> control on set of exported methods
>> is workaround to reduce library file size (and size has impact on 
>> memory footprint, download footprint, startup time, etc.).
>>
> I don't know how much it helps any of these but the principal reason 
> has always been to avoid
> potential name space clashes. For the most part the only symbols that 
> need to be exported are
> the names of JNI methods. ie the entry points from Java code into native.
>
> -phil.
>