I tried to build jdk9/dev on Fedora22 with GCC 5.1.1, however, it was failed.
I found several problems:


 System:
  Fedora release 22 (Twenty Two) x86_64
   - gcc-5.1.1-1.fc22.x86_64


 Problems:
   1. Array bounds check in GCC
     - jdk/src/java.desktop/share/native/libjavajpeg/jcmaster.c
     - jdk/src/java.desktop/share/native/libjavajpeg/jquant1.c
     - jdk/src/java.desktop/share/native/libmlib_image/mlib_ImageLookUp_64.c
     - jdk/src/java.desktop/share/native/libmlib_image/mlib_c_ImageLookUp_f.c

     It seems to be bug of GCC:
       Bug 59124: [4.8/4.9/5/6 Regression] Wrong warnings "array subscript is above array bounds"
       https://gcc.gnu.org/bugzilla/show_bug.cgi?id=59124

     I think implementations of these files have no problem.
     So I propose to ignore warning(s) of compiler through pragma option as
     workaround when we use GCC [1].


   2. Local variables might be clobbered
     - jdk/src/java.desktop/share/native/libsplashscreen/splashscreen_png.c

     SplashDecodePng() calls setjmp(3).
     Some local variables initialize before setjmp() call, and use after it.
     Their initial values are only used at cleanup code (*done* label) and
     actual values are stored only after setjmp() call.
     So I think we can ignore this error through pragma option [1].


   3. Incorrect condition
     - jdk/src/jdk.jdwp.agent/share/native/libjdwp/eventFilter.c

     searchAllSourceNames() returns int value. However, branch condition in
     eventFilterRestricted_passesFilter() treats it as boolean value.


[1] https://gcc.gnu.org/onlinedocs/gcc/Diagnostic-Pragmas.html