Warning message when build protobuf lite

[yejw5]

Version: Ubuntu 16.0.4, bazel 0.12.0, protobuf v3.4.0/v3.5.1

When add protobuf lite C++ as deps of my project and build with bazel tools, there are some -Wunused-parameter warnings. We hope to build our project with --copt=-Werror, these warnings will report as errors and terminate building process. Is there any plan to fix this situation?

The total warning log as follows:

INFO: From Compiling external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:325:37: warning: unused parameter 'cached_s
ize' [-Wunused-parameter]
                               int32 cached_size, ArrayOutput* output) {
                                     ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:690:73: warning: unused parameter 'tag' [-W
unused-parameter]
 void UnknownFieldSerializerLite(const uint8* ptr, uint32 offset, uint32 tag,
                                                                         ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:691:40: warning: unused parameter 'has_offs
et' [-Wunused-parameter]
                                 uint32 has_offset,
                                        ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc: In instantiation of 'static void google::p
rotobuf::internal::PackedFieldHelper<9>::Serialize(const void*, const google::protobuf::internal::FieldMetadata&, O*) 
[with O = google::protobuf::io::CodedOutputStream]':
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:610:7:   required from here
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:508:37: warning: unused parameter 'field' [
-Wunused-parameter]
   static void Serialize(const void* field, const FieldMetadata& md, O* output) {
                                     ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:508:72: warning: unused parameter 'output' 
[-Wunused-parameter]
   static void Serialize(const void* field, const FieldMetadata& md, O* output) {
                                                                        ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc: In instantiation of 'static void google::p
rotobuf::internal::PackedFieldHelper<9>::Serialize(const void*, const google::protobuf::internal::FieldMetadata&, O*) 
[with O = google::protobuf::internal::ArrayOutput]':
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:653:7:   required from here
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:508:37: warning: unused parameter 'field' [
-Wunused-parameter]
   static void Serialize(const void* field, const FieldMetadata& md, O* output) {
                                     ^
external/com_google_protobuf/src/google/protobuf/generated_message_util.cc:508:72: warning: unused parameter 'output' 
[-Wunused-parameter]
   static void Serialize(const void* field, const FieldMetadata& md, O* output) {

[acozzette]

I would recommend avoiding using -Werror and strict warnings for protobuf generated code. Since it's machine-generated code, it often has an un-idiomatic style and it would require extra complexity to try to make the code generator smart enough to avoid all warnings.

[hlopko]

Hello all,

we discussed this internally in the context of this Bazel pull request and we reached the conclusion that protoc should to the best of its efforts not produce warning-triggering code. I expect that protobuf team will reopen this issue (or reference a new tracking issue for this effort) soon.

Thank you!

[yejw5]

@hlopko @acozzette Many thanks！

[logankaser]

Any updates?, these warnings are make it very hard to see the warnings in my local code by producing so many errors.

[keith]

These warnings are fixed, and warnings as errors are enabled on CI now. The current RC release should show no warnings.

[logankaser]

I'm getting warnings from:

protobuf/src/google/protobuf/map_type_handler.h

Line 531 in b4f1937

const char* begin, ParseContext* ctx, MapEntryAccessorType* value) { \

(ctx is unused)
and

protobuf/src/google/protobuf/arena.h

Line 690 in b4f1937

PROTOBUF_ALWAYS_INLINE static Arena* GetArenaInternal(const T* value) {

(value is unused)
Maybe this is a seperate issue?

edit:
RC release..., my mistake I was building off master because I was cross compiling to WASM
and thus had to make my own release.
Those warnings will probably not make it past CI then. (I assume this means CI is only run on releases not on pulls into master)

[keith]

Here's the CI command being run

protobuf/kokoro/linux/bazel/build.sh

Lines 9 to 10 in fcfc47d

	git submodule update --init --recursive
	bazel test :protobuf_test --copt=-Werror --host_copt=-Werror

so it depends if you can reproduce it building this specific target. If not maybe we should add these flags elsewhere too

[BSBandme]

Deprioritize to p3 as this may not happen in the near future.

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