Fixing gcc8's no-unknown-warning-option issue.

Before gcc8, it was ignoring any unknown -Wno-* command, leaving clang's
-Wno-unknown-warning-option to mix. That's no longer the case.

Makefile

@@ -330,6 +330,12 @@ ifeq ($(HAS_WORKING_NO_MAYBE_UNINITIALIZED),true)
 W_NO_MAYBE_UNINITIALIZED=-Wno-maybe-uninitialized
 NO_W_NO_MAYBE_UNINITIALIZED=-Wmaybe-uninitialized
 endif
+CHECK_NO_UNKNOWN_WARNING_OPTION_WORKS_CMD = $(CC) -std=c99 -Werror -Wno-unknown-warning-option -o $(TMPOUT) -c test/build/no-unknown-warning-option.c
+HAS_WORKING_NO_UNKNOWN_WARNING_OPTION = $(shell $(CHECK_NO_UNKNOWN_WARNING_OPTION_WORKS_CMD) 2> /dev/null && echo true || echo false)
+ifeq ($(HAS_WORKING_NO_UNKNOWN_WARNING_OPTION),true)
+W_NO_UNKNOWN_WARNING_OPTION=-Wno-unknown-warning-option
+NO_W_NO_UNKNOWN_WARNING_OPTION=-Wunknown-warning-option
+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
@@ -348,7 +354,7 @@ CXXFLAGS += -stdlib=libc++
 LDFLAGS += -framework CoreFoundation
 endif
 CXXFLAGS += -Wnon-virtual-dtor
-CPPFLAGS += -g -Wall -Wextra -Werror -Wno-unknown-warning-option -Wno-long-long -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers -Wno-maybe-uninitialized -DPB_FIELD_32BIT -DOSATOMIC_USE_INLINED=1 -Ithird_party/nanopb -Ithird_party/upb -Isrc/core/ext/upb-generated
+CPPFLAGS += -g -Wall -Wextra -Werror $(W_NO_UNKNOWN_WARNING_OPTION) -Wno-long-long -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers -Wno-maybe-uninitialized -DPB_FIELD_32BIT -DOSATOMIC_USE_INLINED=1 -Ithird_party/nanopb -Ithird_party/upb -Isrc/core/ext/upb-generated
 COREFLAGS += -fno-rtti -fno-exceptions
 LDFLAGS += -g
 

build.yaml

@@ -6199,7 +6199,7 @@ defaults:
     CXXFLAGS: $(W_NO_CXX14_COMPAT)
   global:
     COREFLAGS: -fno-rtti -fno-exceptions
-    CPPFLAGS: -g -Wall -Wextra -Werror -Wno-unknown-warning-option -Wno-long-long
+    CPPFLAGS: -g -Wall -Wextra -Werror $(W_NO_UNKNOWN_WARNING_OPTION) -Wno-long-long
       -Wno-unused-parameter -Wno-deprecated-declarations -Wno-sign-conversion -Wno-shadow
       -Wno-conversion -Wno-implicit-fallthrough -Wno-sign-compare -Wno-missing-field-initializers
       -Wno-maybe-uninitialized -DPB_FIELD_32BIT -DOSATOMIC_USE_INLINED=1 -Ithird_party/nanopb

grpc.gyp

@@ -55,7 +55,7 @@
       '-Wall',
       '-Wextra',
       '-Werror',
-      '-Wno-unknown-warning-option',
+      '$(W_NO_UNKNOWN_WARNING_OPTION)',
       '-Wno-long-long',
       '-Wno-unused-parameter',
       '-Wno-deprecated-declarations',
@@ -146,7 +146,7 @@
             '-Wall',
             '-Wextra',
             '-Werror',
-            '-Wno-unknown-warning-option',
+            '$(W_NO_UNKNOWN_WARNING_OPTION)',
             '-Wno-long-long',
             '-Wno-unused-parameter',
             '-Wno-deprecated-declarations',
@@ -168,7 +168,7 @@
             '-Wall',
             '-Wextra',
             '-Werror',
-            '-Wno-unknown-warning-option',
+            '$(W_NO_UNKNOWN_WARNING_OPTION)',
             '-Wno-long-long',
             '-Wno-unused-parameter',
             '-Wno-deprecated-declarations',

templates/Makefile.template

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