Merge pull request #4871 from ctiller/mwah

Fix a build error on newer clangs with msan

Makefile

@@ -279,6 +279,12 @@ endif
 CXX11_CHECK_CMD = $(CXX) -std=c++11 -o $(TMPOUT) -c test/build/c++11.cc
 HAS_CXX11 = $(shell $(CXX11_CHECK_CMD) 2> /dev/null && echo true || echo false)
 
+CHECK_NO_SHIFT_NEGATIVE_VALUE_CMD = $(CC) -std=c99 -Werror -Wno-shift-negative-value -o $(TMPOUT) -c test/build/empty.c
+HAS_NO_SHIFT_NEGATIVE_VALUE = $(shell $(CHECK_NO_SHIFT_NEGATIVE_VALUE_CMD) 2> /dev/null && echo true || echo false)
+ifeq ($(HAS_NO_SHIFT_NEGATIVE_VALUE),true)
+W_NO_SHIFT_NEGATIVE_VALUE=-Wno-shift-negative-value
+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
 # cross-compiling, you can override these variables from GNU make's
@@ -5485,7 +5491,7 @@ LIBZ_SRC = \
 
 LIBZ_OBJS = $(addprefix $(OBJDIR)/$(CONFIG)/, $(addsuffix .o, $(basename $(LIBZ_SRC))))
 
-$(LIBZ_OBJS): CFLAGS := $(CFLAGS) -Wno-sign-conversion -Wno-conversion -Wno-unused-value -Wno-implicit-function-declaration -fvisibility=hidden
+$(LIBZ_OBJS): CFLAGS := $(CFLAGS) -Wno-sign-conversion -Wno-conversion -Wno-unused-value -Wno-implicit-function-declaration $(W_NO_SHIFT_NEGATIVE_VALUE) -fvisibility=hidden
 
 $(LIBDIR)/$(CONFIG)/libz.a: $(ZLIB_DEP) $(OPENSSL_DEP)  $(LIBZ_OBJS)
 	$(E) "[AR]      Creating $@"

templates/Makefile.template

@@ -183,6 +183,12 @@
   CXX11_CHECK_CMD = $(CXX) -std=c++11 -o $(TMPOUT) -c test/build/c++11.cc
   HAS_CXX11 = $(shell $(CXX11_CHECK_CMD) 2> /dev/null && echo true || echo false)
 
+  CHECK_NO_SHIFT_NEGATIVE_VALUE_CMD = $(CC) -std=c99 -Werror -Wno-shift-negative-value -o $(TMPOUT) -c test/build/empty.c
+  HAS_NO_SHIFT_NEGATIVE_VALUE = $(shell $(CHECK_NO_SHIFT_NEGATIVE_VALUE_CMD) 2> /dev/null && echo true || echo false)
+  ifeq ($(HAS_NO_SHIFT_NEGATIVE_VALUE),true)
+  W_NO_SHIFT_NEGATIVE_VALUE=-Wno-shift-negative-value
+  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
   # cross-compiling, you can override these variables from GNU make's
@@ -1437,7 +1443,7 @@
   $(LIB${lib.name.upper()}_OBJS): CXXFLAGS := -Ithird_party/boringssl/include $(CXXFLAGS) -fvisibility=hidden
   $(LIB${lib.name.upper()}_OBJS): CPPFLAGS += -DOPENSSL_NO_ASM -D_GNU_SOURCE
   % elif lib.zlib:
-  $(LIB${lib.name.upper()}_OBJS): CFLAGS := $(CFLAGS) -Wno-sign-conversion -Wno-conversion -Wno-unused-value -Wno-implicit-function-declaration -fvisibility=hidden
+  $(LIB${lib.name.upper()}_OBJS): CFLAGS := $(CFLAGS) -Wno-sign-conversion -Wno-conversion -Wno-unused-value -Wno-implicit-function-declaration $(W_NO_SHIFT_NEGATIVE_VALUE) -fvisibility=hidden
   % else:
   % endif