Here are the 4 issues that need fixing (clean-up) in order to compile hotspot with c++11:

#1 src/share/vm/utilities/debug.hpp

/Volumes/Work/jdk10/hotspot/src/share/vm/utilities/vmError.cpp:450:13: error: case value evaluates to 3758096384, which cannot be narrowed to type 'int' [-Wc++11-narrowing]
       case INTERNAL_ERROR:
            ^
/Volumes/Work/jdk10/hotspot/src/share/vm/utilities/vmError.cpp:424:13: error: case value evaluates to 3758096386, which cannot be narrowed to type 'int' [-Wc++11-narrowing]
       case OOM_MMAP_ERROR:
            ^
/Volumes/Work/jdk10/hotspot/src/share/vm/utilities/vmError.cpp:423:13: error: case value evaluates to 3758096385, which cannot be narrowed to type 'int' [-Wc++11-narrowing]
       case OOM_MALLOC_ERROR:

#2 src/share/vm/compiler/methodMatcher.cpp

/Volumes/Work/jdk10/hotspot/src/share/vm/compiler/methodMatcher.cpp:99:19: error: comparison between pointer and integer ('char *' and 'int')
    if (colon + 2 != '\0') {
        ~~~~~~~~~ ^ ~~~~

#3 src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp

/Volumes/Work/jdk10/hotspot/src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp:282:19: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
  __asm__("mov %%"SPELL_REG_SP", %0":"=r"(esp));
                  ^
/Volumes/Work/jdk10/hotspot/src/os_cpu/bsd_x86/vm/os_bsd_x86.cpp:418:19: error: invalid suffix on literal; C++11 requires a space between literal and identifier [-Wreserved-user-defined-literal]
  __asm__("mov %%"SPELL_REG_FP", %0":"=r"(ebp));

#4 src/share/vm/code/compiledIC.cpp

/Volumes/Work/jdk10/hotspot/src/share/vm/code/compiledIC.cpp:227:15: error: comparison between pointer and integer ('address' (aka 'unsigned char *') and 'int')
    if (entry == false) {
        ~~~~~ ^ ~~~~~