clang-8.0 @8.0.0 building libfuzzer fails on darwin 13 and less

[kencu (Ken)]

This is a truly weird one. In a part of the clang-8.0 build, cmake chooses to build it against the iPhoneSimulator.sdk with -miphoneos-version-min=8.0 and this fails the thread_local test. clang-7.0 and clang-devel don't build against darwin12 either, most likely for the same reason.

cd /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/build/projects/compiler-rt/lib/fuzzer && /opt/local/bin/clang++-mp-3.7  -D__STDC_CONSTANT_MACROS -D__STDC_FORMAT_MACROS -D__STDC_LIMIT_MACROS -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/build/projects/compiler-rt/lib/fuzzer -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/llvm-8.0.0.src/projects/compiler-rt/lib/fuzzer -I//opt/local/include/libxml2 -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/build/include -I/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/llvm-8.0.0.src/include  -pipe -Os -std=c++11 -stdlib=libc++ -fPIC -fvisibility-inlines-hidden -Werror=date-time -std=c++11 -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wimplicit-fallthrough -Wcovered-switch-default -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wstring-conversion -Wall -std=c++11 -DNDEBUG -arch x86_64    -stdlib=libc++ -miphoneos-version-min=8.0 -isysroot /Applications/Xcode.app/Contents/Developer/Platforms/iPhoneSimulator.platform/Developer/SDKs/iPhoneSimulator7.1.sdk -fPIC -fno-builtin -fno-exceptions -funwind-tables -fno-stack-protector -fno-sanitize=safe-stack -fvisibility=hidden -fno-lto -O3 -gline-tables-only -fno-omit-frame-pointer -o CMakeFiles/RTfuzzer.iossim.dir/FuzzerDriver.cpp.o -c /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/llvm-8.0.0.src/projects/compiler-rt/lib/fuzzer/FuzzerDriver.cpp

In file included from /opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/llvm-8.0.0.src/projects/compiler-rt/lib/fuzzer/FuzzerDriver.cpp:16:
/opt/local/var/macports/build/_opt_local_var_macports_sources_rsync.macports.org_macports_release_tarballs_ports_lang_llvm-8.0/clang-8.0/work/llvm-8.0.0.src/projects/compiler-rt/lib/fuzzer/FuzzerInternal.h:151:10: error: thread-local storage is not supported for the current target
  static thread_local bool IsMyThread;
         ^

[kencu (Ken)]

In 4d5d3045665dc3c8138d613e2e26b7f0889ff1e6/macports-ports (master):

clang-7.0/8.0/devel: disable fuzzer on <= 10.8

there is an unusual error in the libfuzzer cmake logic
that makes it build against the iphonesimulator SDK
this fails the thread_local test

see: #58291

[ken-cunningham-webuse]

In 72fdf7eff7635f11ab5342d86683da10fb08eccd/macports-ports (master):

clang-7.0/8.0/devel: turn off libfuzzer on 10.9

most of the other analyzers are already turned off on 10.9
libfuzzer does not build on 10.9 with our current compiler defaults
which lead it to clang-3.7

it may be possible to rearrange these defaults to use another
macports-clang version to re-enable some of these supporting
features and analyzers on 10.9 (and perhaps earlier) if there
is interest

closes: #58952
see: #58291

[kencu (Ken)]

It is possible that building with a newer macports clang compiler could fix the build of libfuzzer, and perhaps some other components, on some of these older systems.

[kencu (Ken)]

fuzzer has been disabled on systems where it doesn't build