Debugging

Frequently asked questions and debugging scenarios encountered by protobuf users.

Bazel: Resolving Issues with Prebuilt Protoc

As mentioned in this news article, Bazel 7 and later support builds that use a prebuilt protoc. When everything is configured correctly, this can save a lot of time building, reduce logging volume, and eliminate the need for C++ toolchain in non-C++ implementations.

To prevent protoc compilation from source, add the following to your .bazelrc file:

common --per_file_copt=external/.*protobuf.*@--PROTOBUF_WAS_NOT_SUPPOSED_TO_BE_BUILT
common --host_per_file_copt=external/.*protobuf.*@--PROTOBUF_WAS_NOT_SUPPOSED_TO_BE_BUILT
common --per_file_copt=external/.*grpc.*@--GRPC_WAS_NOT_SUPPOSED_TO_BE_BUILT
common --host_per_file_copt=external/.*grpc.*@--GRPC_WAS_NOT_SUPPOSED_TO_BE_BUILT

When there are hard-coded references to @com_google_protobuf//:protoc that are reachable by the dependency graph, protoc will force it to be built for those cases, negating this benefit. To resolve this, you’ll need to find where the dependencies are and request that those rulesets be updated.

To find where you depend on protoc, use the following command:

bazel cquery 'somepath("//...", "@com_google_protobuf//:all")'

Note: Prebuilts are only available for our standard set of platforms. Anyone on a nonstandard platform will have to build protoc from source.