RFR [XS]: 8208744: remove unneeded -DUSE_MMAP settings for JDK native libs builds -was : RE: unneeded -DUSE_MMAP in JDK native libs builds

[Baesken, Matthias]

Hello,  I can confirm what David said . 
Additionally I grepped through /usr/include on my Linux machine and did not  find any  USE_MMAP occurences.

I created this  webrev +  bug :

http://cr.openjdk.java.net/~mbaesken/webrevs/8208744/

https://bugs.openjdk.java.net/browse/JDK-8208744


Please review !


Thanks, Matthias


> -----Original Message-----
> From: David Holmes <david.holmes at oracle.com>
> Sent: Freitag, 3. August 2018 02:56
> To: Magnus Ihse Bursie <magnus.ihse.bursie at oracle.com>; Baesken,
> Matthias <matthias.baesken at sap.com>
> Cc: build-dev at openjdk.java.net
> Subject: Re: unneeded -DUSE_MMAP in JDK native libs builds
> 
> On 3/08/2018 3:44 AM, Magnus Ihse Bursie wrote:
> >
> >> 2 aug. 2018 kl. 05:33 skrev Baesken, Matthias
> <matthias.baesken at sap.com>:
> >>
> >> Hello I noticed that   -DUSE_MMAP  is set for these  JDK native libs, but I
> cannot find it in the code   (for libzip it is different there the flag shows up in
> the code too ) :
> >
> > I've always assumed that this was used to control the behavior in some
> imported header files. Have you verified that this is not the case?
> 
> It is only used in
> 
> ./java.base/share/native/libzip/zip_util.c
> ./java.base/share/native/libzip/zip_util.h
> 
> and the header itself is only included in the .c file. So unless this
> source file is used for the other libraries (which I don't see) then we
> don't need -DUSE_MMAP when building them.
> 
> AFAIKS the use of this for BUILD_LIBDT_SOCKET and BUILD_LIBDT_SHMEM
> dates back to the build-infra changes in JDK 8.
> 
> http://hg.openjdk.java.net/jdk8/jdk8/jdk/rev/9d3d01aca52c
> 
> But I can't see why it was introduced there.
> 
> In JDK 7 it's only applied to the zip library.
> 
> Cheers,
> David
> -----
> 
> >
> > /Magnus
> >
> >>
> >> Lib-jdk.jdi.gmk  :
> >>
> >> 32  $(eval $(call SetupJdkLibrary, BUILD_LIBDT_SHMEM, \
> >> ......
> >> 35 CFLAGS := $(CFLAGS_JDKLIB) -DUSE_MMAP, \
> >>
> >>
> >> Lib-jdk.jdwp.agent.gmk :
> >>
> >> 30 $(eval $(call SetupJdkLibrary, BUILD_LIBDT_SOCKET, \
> >> ......
> >> 33 CFLAGS := $(CFLAGS_JDKLIB) -DUSE_MMAP \
> >>
> >>
> >> Any objections  to remove those  2    -DUSE_MMAP    settings ?
> >> If it is fine to remove I would prepare a  webrev .
> >>
> >> Thanks, Matthias
> >