Add a mutex lock/unlock inside every public API function.

Author: iphydf

.cirrus.yml

@@ -1,7 +1,7 @@
 ---
 cirrus-ci_task:
   container:
-    image: l.gcr.io/google/bazel:2.1.0
+    image: l.gcr.io/google/bazel:2.2.0
     cpu: 8
     memory: 12G
   configure_script:

.travis/bazel-linux

@@ -6,9 +6,9 @@ set -eu
 
 travis_install() {
   # Get bazel.
-  wget https://github.com/bazelbuild/bazel/releases/download/2.1.1/bazel-2.1.1-installer-linux-x86_64.sh
-  chmod +x bazel-2.1.1-installer-linux-x86_64.sh
-  ./bazel-2.1.1-installer-linux-x86_64.sh --user
+  wget https://github.com/bazelbuild/bazel/releases/download/2.2.0/bazel-2.2.0-installer-linux-x86_64.sh
+  chmod +x bazel-2.2.0-installer-linux-x86_64.sh
+  ./bazel-2.2.0-installer-linux-x86_64.sh --user
   echo 'build --jobs=4 --curses=no --verbose_failures' >> $HOME/.bazelrc
   echo 'build --config=linux' >> $HOME/.bazelrc
   echo "build --config=$CC" >> $HOME/.bazelrc

toxcore/tox.api.h

@@ -623,6 +623,21 @@ static class options {
        */
       any user_data;
     }
+
+    /**
+     * These options are experimental, so avoid writing code that depends on
+     * them. Options marked "experimental" may change their behaviour or go away
+     * entirely in the future, or may be renamed to something non-experimental
+     * if they become part of the supported API.
+     */
+    namespace experimental {
+      /**
+       * Make public API functions thread-safe using a per-instance lock.
+       *
+       * Default: false.
+       */
+      bool thread_safety;
+    }
   }