!@#!%$@#

Makefile

@@ -330,6 +330,12 @@ ifeq ($(HAS_WORKING_NO_UNUSED_BUT_SET_VARIABLE),true)
 W_NO_UNUSED_BUT_SET_VARIABLE=-Wno-unused-but-set-variable
 NO_W_NO_UNUSED_BUT_SET_VARIABLE=-Wunused-but-set-variable
 endif
+CHECK_NO_MAYBE_UNINITIALIZED_WORKS_CMD = $(CC) -std=c99 -Werror -Wno-maybe-uninitialized -o $(TMPOUT) -c test/build/no-maybe-uninitialized.c
+HAS_WORKING_NO_MAYBE_UNINITIALIZED = $(shell $(CHECK_NO_MAYBE_UNINITIALIZED_WORKS_CMD) 2> /dev/null && echo true || echo false)
+ifeq ($(HAS_WORKING_NO_MAYBE_UNINITIALIZED),true)
+W_NO_MAYBE_UNINITIALIZED=-Wno-maybe-uninitialized
+NO_W_NO_MAYBE_UNINITIALIZED=-Wmaybe-uninitialized
+endif
 
 # The HOST compiler settings are used to compile the protoc plugins.
 # In most cases, you won't have to change anything, but if you are
@@ -3214,7 +3220,7 @@ PUBLIC_HEADERS_C += \
 
 LIBCXXABI_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(LIBCXXABI_SRC))))
 
-$(LIBCXXABI_OBJS): CPPFLAGS += -D_LIBCPP_DISABLE_EXTERN_TEMPLATE -D_LIBCXXABI_BUILDING_LIBRARY -D_LIBCXXABI_NO_EXCEPTIONS -Ithird_party/libcxxabi/include -nostdinc++ -Ithird_party/libcxx/include $(W_NO_UNUSED_BUT_SET_VARIABLE) -fvisibility=hidden
+$(LIBCXXABI_OBJS): CPPFLAGS += -D_LIBCPP_DISABLE_EXTERN_TEMPLATE -D_LIBCXXABI_BUILDING_LIBRARY -D_LIBCXXABI_NO_EXCEPTIONS -Ithird_party/libcxxabi/include -nostdinc++ -Ithird_party/libcxx/include $(W_NO_UNUSED_BUT_SET_VARIABLE) $(W_NO_MAYBE_UNINITIALIZED) -fvisibility=hidden
 $(LIBCXXABI_OBJS): CXXFLAGS += $(W_NO_CXX14_COMPAT)
 
 $(LIBDIR)/$(CONFIG)/libcxxabi.a: $(ZLIB_DEP) $(CARES_DEP) $(ADDRESS_SORTING_DEP)  $(LIBCXXABI_OBJS) 

build.yaml

@@ -5694,7 +5694,7 @@ defaults:
   cxxabi:
     CPPFLAGS: -D_LIBCPP_DISABLE_EXTERN_TEMPLATE -D_LIBCXXABI_BUILDING_LIBRARY -D_LIBCXXABI_NO_EXCEPTIONS
       -Ithird_party/libcxxabi/include -nostdinc++ -Ithird_party/libcxx/include $(W_NO_UNUSED_BUT_SET_VARIABLE)
-      -fvisibility=hidden
+      $(W_NO_MAYBE_UNINITIALIZED) -fvisibility=hidden
     CXXFLAGS: $(W_NO_CXX14_COMPAT)
   global:
     COREFLAGS: -fno-rtti -fno-exceptions

templates/Makefile.template

@@ -37,7 +37,7 @@
 
     # warnings we'd like, but that dont exist in all compilers
     PREFERRED_WARNINGS=['shadow', 'extra-semi']
-    CHECK_WARNINGS=PREFERRED_WARNINGS + ['no-shift-negative-value', 'no-unused-but-set-variable']
+    CHECK_WARNINGS=PREFERRED_WARNINGS + ['no-shift-negative-value', 'no-unused-but-set-variable', 'no-maybe-uninitialized']
 
     def warning_var(fmt, warning):
       return fmt % warning.replace('-', '_').replace('+', 'X').upper()

test/build/no-maybe-uninitialized.c

@@ -0,0 +1,19 @@
+/*
+ *
+ * Copyright 2015 gRPC authors.
+ *
+ * Licensed under the Apache License, Version 2.0 (the "License");
+ * you may not use this file except in compliance with the License.
+ * You may obtain a copy of the License at
+ *
+ *     http://www.apache.org/licenses/LICENSE-2.0
+ *
+ * Unless required by applicable law or agreed to in writing, software
+ * distributed under the License is distributed on an "AS IS" BASIS,
+ * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
+ * See the License for the specific language governing permissions and
+ * limitations under the License.
+ *
+ */
+
+int main(void) {}