--- a/aclocal.m4
+++ b/aclocal.m4
@@ -12,16 +12,17 @@ builtin(include, build/autoconf/codeset.
 builtin(include, build/autoconf/altoptions.m4)dnl
 builtin(include, build/autoconf/mozprog.m4)dnl
 builtin(include, build/autoconf/mozheader.m4)dnl
 builtin(include, build/autoconf/mozcommonheader.m4)dnl
 builtin(include, build/autoconf/acwinpaths.m4)dnl
 builtin(include, build/autoconf/lto.m4)dnl
 builtin(include, build/autoconf/gcc-pr49911.m4)dnl
 builtin(include, build/autoconf/frameptr.m4)dnl
+builtin(include, build/autoconf/compiler-opts.m4)dnl
 
 MOZ_PROG_CHECKMSYS()
 
 # Read the user's .mozconfig script.  We can't do this in
 # configure.in: autoconf puts the argument parsing code above anything
 # expanded from configure.in, and we need to get the configure options
 # from .mozconfig in place before that argument parsing code.
 MOZ_READ_MOZCONFIG(.)

new file mode 100644
--- /dev/null
+++ b/build/autoconf/compiler-opts.m4
@@ -0,0 +1,13 @@
+dnl Add compiler specific options
+
+AC_DEFUN([MOZ_COMPILER_OPTS],
+[
+if test "$CLANG_CXX"; then
+    ## We disable return-type-c-linkage because jsval is defined as a C++ type but is
+    ## returned by C functions. This is possible because we use knowledge about the ABI
+    ## to typedef it to a C type with the same layout when the headers are included
+    ## from C.
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-return-type-c-linkage"
+fi
+])
+

--- a/configure.in
+++ b/configure.in
@@ -3338,16 +3338,17 @@ fi         # GNU_CC
 if test "$SOLARIS_SUNPRO_CC"; then
 VISIBILITY_FLAGS='-xldscope=hidden'
 fi         # Sun Studio on Solaris
 
 AC_SUBST(WRAP_SYSTEM_INCLUDES)
 AC_SUBST(VISIBILITY_FLAGS)
 
 MOZ_GCC_PR49911
+MOZ_COMPILER_OPTS
 
 dnl Check for __force_align_arg_pointer__ for SSE2 on gcc
 dnl ========================================================
 if test "$GNU_CC"; then
   CFLAGS_save="${CFLAGS}"
   CFLAGS="${CFLAGS} -Werror"
   AC_CACHE_CHECK(for __force_align_arg_pointer__ attribute,
                  ac_cv_force_align_arg_pointer,

--- a/js/src/aclocal.m4
+++ b/js/src/aclocal.m4
@@ -9,10 +9,11 @@ builtin(include, build/autoconf/altoptio
 builtin(include, build/autoconf/moznbytetype.m4)dnl
 builtin(include, build/autoconf/mozprog.m4)dnl
 builtin(include, build/autoconf/mozheader.m4)dnl
 builtin(include, build/autoconf/mozcommonheader.m4)dnl
 builtin(include, build/autoconf/acwinpaths.m4)dnl
 builtin(include, build/autoconf/lto.m4)dnl
 builtin(include, build/autoconf/gcc-pr49911.m4)dnl
 builtin(include, build/autoconf/frameptr.m4)dnl
+builtin(include, build/autoconf/compiler-opts.m4)dnl
 
 MOZ_PROG_CHECKMSYS()

new file mode 100644
--- /dev/null
+++ b/js/src/build/autoconf/compiler-opts.m4
@@ -0,0 +1,13 @@
+dnl Add compiler specific options
+
+AC_DEFUN([MOZ_COMPILER_OPTS],
+[
+if test "$CLANG_CXX"; then
+    ## We disable return-type-c-linkage because jsval is defined as a C++ type but is
+    ## returned by C functions. This is possible because we use knowledge about the ABI
+    ## to typedef it to a C type with the same layout when the headers are included
+    ## from C.
+    _WARNINGS_CXXFLAGS="${_WARNINGS_CXXFLAGS} -Wno-return-type-c-linkage"
+fi
+])
+

--- a/js/src/configure.in
+++ b/js/src/configure.in
@@ -3128,16 +3128,17 @@ fi         # GNU_CC
 if test "$SOLARIS_SUNPRO_CC"; then
 VISIBILITY_FLAGS='-xldscope=hidden'
 fi         # Sun Studio on Solaris
 
 AC_SUBST(WRAP_SYSTEM_INCLUDES)
 AC_SUBST(VISIBILITY_FLAGS)
 
 MOZ_GCC_PR49911
+MOZ_COMPILER_OPTS
 
 dnl Check for __force_align_arg_pointer__ for SSE2 on gcc
 dnl ========================================================
 if test "$GNU_CC"; then
   CFLAGS_save="${CFLAGS}"
   CFLAGS="${CFLAGS} -Werror"
   AC_CACHE_CHECK(for __force_align_arg_pointer__ attribute,
                  ac_cv_force_align_arg_pointer,