While trying to build GHC 8.0.1 on FreeBSD 11.x, I come across following compiler error:

/usr/local/bin/clang-cpp38  -DPROFILING -DTHREADED_RTS -DDEBUG  -fno-stack-protector -O2 -pipe  -Qunused-arguments -I/usr/local/include -fstack-protector -fno-strict-aliasing -Wall  -Wall -Wextra -Wstrict-prototypes  -Wmissing-prototypes  -Wmissing-declarations -Winline -Waggregate-return -Wpointer-arith -Wmissing-noreturn -Wnested-externs -Wredundant-decls  -Iincludes -Iincludes/dist -Iincludes/dist-derivedconstants/header -Iincludes/dist-ghcconstants/header -Irts -Irts/dist/build -DCOMPILING_RTS -fno-strict-aliasing -fno-common -Irts/dist/build/autogen        -Wno-unknown-pragmas -O2 -fomit-frame-pointer -g -DRtsWay=\"rts_v\"     -MM -x c rts/posix/OSMem.c -MF rts/dist/build/.depend-v-p-dyn-l-debug-thr-thr_debug-thr_l-thr_p-debug_dyn-thr_dyn-thr_debug_dyn-l_dyn-thr_l_dyn.c_asm.bit
rts/posix/OSMem.c:158:5: error: USE_LARGE_ADDRESS_SPACE needs MAP_NORESERVE
#   error USE_LARGE_ADDRESS_SPACE needs MAP_NORESERVE
    ^
1 error generated.

From some investigation, it turns out when it was there, it was not even implemented. The value of __FreeBSD_version (in case you plan to add conditional based on it), where it is changed is 1100039.

Let me know if you need more information.

Thanks for looking