RFR: 8187667: Disable deprecation warning for readdir_r

[David Holmes]

Hi Erik,

Reviewed!

On 19/09/2017 10:42 PM, Erik Helin wrote:
> Hi all,
> 
> I'm continuing to run into some small problems when compiling HotSpot 
> with a more recent toolchain. It seems like readdir_r [0] has been 
> deprecated beginning with glibc 2.24 [1]. In HotSpot, we use readdir_r 
> for os::readdir on Linux (defined in os_linux.inline.hpp). Since 
> readdir_r most likely will stay around for a long time in glibc (even 
> though in deprecated form), I figured it was best to just silence the 
> deprecation warning from gcc. If readdir_r finally is removed one day, 
> then we might have to look up the appropriate readdir function using 
> dlopen, dlsym etc.

I find it very odd that they have deprecated the thread-safe variant of 
this function, and recommend use of the basic readdir. I can only assume 
they have made readdir itself thread-safe, but given the POSIX spec does 
not require that, noone can take advantage without locking into knowing 
which glibc version they are running on! That seems an awful mess for 
programmers.

It is a good idea to just keep using it.

> Patch:
> http://cr.openjdk.java.net/~ehelin/8187667/00/
> 
> Bug:
> https://bugs.openjdk.java.net/browse/JDK-8187667
> 
> Testing:
> - Compiles with:
>    - gcc 7.1.1 and glibc 2.25 on Fedora 26
>    - gcc 4.9.2 and glibc 2.12 on OEL 6.4
> - JPRT

The change will cause warnings on gcc < 4.6, so this reinforces the need 
to switch to our minimim gcc version ... which I forget :)

Thanks,
David


> Thanks,
> Erik
> 
> [0]: http://pubs.opengroup.org/onlinepubs/009695399/functions/readdir.html
> [1]: https://sourceware.org/bugzilla/show_bug.cgi?id=19056