24 files changed, 33 insertions, 12 deletions
diff --git a/src/build-data/os/aix.txt b/src/build-data/os/aix.txt
index 93b689a0a..fd8cf2eb1 100644
--- a/src/build-data/os/aix.txt
+++ b/src/build-data/os/aix.txt
@@ -10,6 +10,7 @@ clock_gettime
 dev_random
 proc_fs
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/android.txt b/src/build-data/os/android.txt
index e55a7e3d3..f8f61f7b4 100644
--- a/src/build-data/os/android.txt
+++ b/src/build-data/os/android.txt
@@ -18,6 +18,7 @@ getauxval
 # Added in API 28
 #getentropy
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/cygwin.txt b/src/build-data/os/cygwin.txt
index 2133c1587..dabc018c3 100644
--- a/src/build-data/os/cygwin.txt
+++ b/src/build-data/os/cygwin.txt
@@ -12,6 +12,7 @@ doc_dir docs
 posix1
 dev_random
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/dragonfly.txt b/src/build-data/os/dragonfly.txt
index 36a9d33b4..f2cc1cb76 100644
--- a/src/build-data/os/dragonfly.txt
+++ b/src/build-data/os/dragonfly.txt
@@ -9,6 +9,7 @@ proc_fs
 dev_random
 arc4random
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/emscripten.txt b/src/build-data/os/emscripten.txt
index b865eff87..0068fb171 100644
--- a/src/build-data/os/emscripten.txt
+++ b/src/build-data/os/emscripten.txt
@@ -10,6 +10,7 @@ ar_options cr
 use_stack_protector no
 
 <target_features>
+atomics
 filesystem
 dev_random
 posix1
diff --git a/src/build-data/os/freebsd.txt b/src/build-data/os/freebsd.txt
index cb8817909..1b9b3817d 100644
--- a/src/build-data/os/freebsd.txt
+++ b/src/build-data/os/freebsd.txt
@@ -14,6 +14,7 @@ cap_enter
 elf_aux_info
 getentropy
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/haiku.txt b/src/build-data/os/haiku.txt
index 9899eb80d..7a4bcbe89 100644
--- a/src/build-data/os/haiku.txt
+++ b/src/build-data/os/haiku.txt
@@ -13,6 +13,7 @@ posix1
 clock_gettime
 dev_random
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/hpux.txt b/src/build-data/os/hpux.txt
index d2b50be94..ea699910c 100644
--- a/src/build-data/os/hpux.txt
+++ b/src/build-data/os/hpux.txt
@@ -8,6 +8,7 @@ posix_mlock
 clock_gettime
 dev_random
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/hurd.txt b/src/build-data/os/hurd.txt
index a5d4fcbd4..589b99e2d 100644
--- a/src/build-data/os/hurd.txt
+++ b/src/build-data/os/hurd.txt
@@ -7,6 +7,7 @@ posix_mlock
 dev_random
 clock_gettime
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/includeos.txt b/src/build-data/os/includeos.txt
index 7d2ebfdc9..7e45eb47c 100644
--- a/src/build-data/os/includeos.txt
+++ b/src/build-data/os/includeos.txt
@@ -1,4 +1,5 @@
 <target_features>
 posix1
 dev_random
+atomics
 </target_features>
diff --git a/src/build-data/os/ios.txt b/src/build-data/os/ios.txt
index 65f0c6fb4..c65f24305 100644
--- a/src/build-data/os/ios.txt
+++ b/src/build-data/os/ios.txt
@@ -11,6 +11,8 @@ posix_mlock
 arc4random
 
 commoncrypto
+
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/linux.txt b/src/build-data/os/linux.txt
index 5d5a36e3c..daf98f2b6 100644
--- a/src/build-data/os/linux.txt
+++ b/src/build-data/os/linux.txt
@@ -14,6 +14,7 @@ getauxval
 #getrandom
 #getentropy
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/llvm.txt b/src/build-data/os/llvm.txt
index 87925142d..0cda2f7e8 100644
--- a/src/build-data/os/llvm.txt
+++ b/src/build-data/os/llvm.txt
@@ -11,4 +11,5 @@ use_stack_protector no
 
 <target_features>
 filesystem
+atomics
 </target_features>
diff --git a/src/build-data/os/macos.txt b/src/build-data/os/macos.txt
index 4349637b8..b603d18df 100644
--- a/src/build-data/os/macos.txt
+++ b/src/build-data/os/macos.txt
@@ -16,12 +16,13 @@ dev_random
 clock_gettime
 
 commoncrypto
+apple_keychain
+
+atomics
 sockets
 threads
 thread_local
 filesystem
-
-apple_keychain
 </target_features>
 
 <aliases>
diff --git a/src/build-data/os/mingw.txt b/src/build-data/os/mingw.txt
index 3f61a4a77..b2cc2f0b8 100644
--- a/src/build-data/os/mingw.txt
+++ b/src/build-data/os/mingw.txt
@@ -25,6 +25,7 @@ win32
 rtlgenrandom
 virtual_lock
 
+atomics
 threads
 thread_local
 filesystem
diff --git a/src/build-data/os/netbsd.txt b/src/build-data/os/netbsd.txt
index f9ee81cb8..9be8a1f8a 100644
--- a/src/build-data/os/netbsd.txt
+++ b/src/build-data/os/netbsd.txt
@@ -9,6 +9,7 @@ dev_random
 arc4random
 explicit_memset
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/openbsd.txt b/src/build-data/os/openbsd.txt
index 4b483273c..70f49e6ac 100644
--- a/src/build-data/os/openbsd.txt
+++ b/src/build-data/os/openbsd.txt
@@ -17,6 +17,7 @@ getentropy
 explicit_bzero
 pledge
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/qnx.txt b/src/build-data/os/qnx.txt
index 658c52da2..feedf5f75 100644
--- a/src/build-data/os/qnx.txt
+++ b/src/build-data/os/qnx.txt
@@ -6,6 +6,7 @@ posix_mlock
 clock_gettime
 dev_random
 
+atomics
 sockets
 threads
 thread_local
diff --git a/src/build-data/os/solaris.txt b/src/build-data/os/solaris.txt
index 3abee02da..29897b788 100644
--- a/src/build-data/os/solaris.txt
+++ b/src/build-data/os/solaris.txt
@@ -8,6 +8,7 @@ clock_gettime
 dev_random
 proc_fs
 
+atomics
 threads
 thread_local
 sockets
diff --git a/src/build-data/os/uwp.txt b/src/build-data/os/uwp.txt
index bda092170..eb79c65ed 100644
--- a/src/build-data/os/uwp.txt
+++ b/src/build-data/os/uwp.txt
@@ -14,6 +14,7 @@ crypto_ng
 
 rtlsecurezeromemory
 
+atomics
 threads
 thread_local
 filesystem
diff --git a/src/build-data/os/windows.txt b/src/build-data/os/windows.txt
index a9abd82fb..07bfefb13 100644
--- a/src/build-data/os/windows.txt
+++ b/src/build-data/os/windows.txt
@@ -34,6 +34,7 @@ rtlsecurezeromemory
 
 virtual_lock
 
+atomics
 threads
 thread_local
 filesystem
diff --git a/src/lib/pubkey/xmss/info.txt b/src/lib/pubkey/xmss/info.txt
index 72b127831..6adc1fda8 100644
--- a/src/lib/pubkey/xmss/info.txt
+++ b/src/lib/pubkey/xmss/info.txt
@@ -33,3 +33,7 @@ rng
 hash
 sha2_32
 </requires>
+
+<os_features>
+atomics
+</os_features>
diff --git a/src/scripts/ci/setup_travis.sh b/src/scripts/ci/setup_travis.sh
index d9d21dd6e..c5451551f 100755
--- a/src/scripts/ci/setup_travis.sh
+++ b/src/scripts/ci/setup_travis.sh
@@ -60,6 +60,9 @@ if [ "$TRAVIS_OS_NAME" = "linux" ]; then
         sudo apt-get -qq update
         sudo apt-get install gcc-arm-none-eabi libstdc++-arm-none-eabi-newlib
 
+        echo 'extern "C" void __sync_synchronize() {}' >> src/tests/main.cpp
+        echo 'extern "C" void __sync_synchronize() {}' >> src/cli/main.cpp
+
     elif [ "$TARGET" = "lint" ]; then
         sudo apt-get -qq update
         sudo apt-get install pylint
diff --git a/src/scripts/ci_build.py b/src/scripts/ci_build.py
index 07c21bf74..bd6828d6e 100755
--- a/src/scripts/ci_build.py
+++ b/src/scripts/ci_build.py
@@ -27,13 +27,9 @@ def get_concurrency():
         return def_concurrency
 
 def build_targets(target, target_os):
-    if target == 'baremetal':
-        yield 'static'
-        return
-
     if target in ['shared', 'mini-shared', 'bsi', 'nist']:
         yield 'shared'
-    elif target in ['static', 'mini-static', 'fuzzers']:
+    elif target in ['static', 'mini-static', 'fuzzers', 'baremetal']:
         yield 'static'
     elif target_os in ['windows']:
         yield 'shared'
@@ -155,7 +151,7 @@ def determine_flags(target, target_os, target_cpu, target_cc, cc_bin,
 
     if target == 'baremetal':
         cc_bin = 'arm-none-eabi-c++'
-        flags += ['--cpu=arm32', '--disable-neon', '--without-stack-protector']
+        flags += ['--cpu=arm32', '--disable-neon', '--without-stack-protector', '--ldflags=-specs=nosys.specs']
         test_cmd = None
 
     if is_cross_target:
@@ -559,10 +555,6 @@ def main(args=None):
             if target in ['coverage']:
                 make_targets += ['bogo_shim']
 
-            if target in ['baremetal']:
-                # everything else builds, but fails to link
-                make_targets = ['libs']
-
             cmds.append(make_prefix + make_cmd + make_targets)
 
             if options.compiler_cache in ccache_show_stats: