lidavidm commented on code in PR #47413:
URL: https://github.com/apache/arrow/pull/47413#discussion_r2299369524
##########
cpp/src/arrow/flight/meson.build:
##########
@@ -52,14 +52,29 @@ fs = import('fs')
protoc = find_program('protoc')
flight_proto_path = fs.parent(meson.project_source_root()) / 'format'
+
+# To ensure messages from proto files are created correctly, we need to
+# pass in dllexport_decl=<...> . Unfortunately, it doesn't appear that we
+# can just pass in dllexport_decl=ARROW_FLIGHT_EXPORT, as the visibility
+# macro won't be easily available to the generated proto file. See also
+# https://github.com/protocolbuffers/protobuf/issues/19422
+if cpp_compiler.get_id() == 'msvc'
+ proto_visibility = '__declspec(dllexport)'
+else
+ proto_visibility = '__attribute__((visibility("default")))'
+endif
+
flight_proto_files = custom_target(
'arrow-flight-proto-files',
input: [flight_proto_path / 'Flight.proto'],
output: ['Flight.pb.cc', 'Flight.pb.h'],
command: [
protoc,
'--proto_path=' + flight_proto_path,
- '--cpp_out=' + meson.current_build_dir(),
+ '--cpp_out=dllexport_decl=@0@:@1@'.format(
Review Comment:
IIRC every time I've tried, it's turned out that `protoc` doesn't actually
insert the dllexport declarations in the right places and you get something
unusable
##########
cpp/src/arrow/flight/meson.build:
##########
@@ -52,14 +52,29 @@ fs = import('fs')
protoc = find_program('protoc')
flight_proto_path = fs.parent(meson.project_source_root()) / 'format'
+
+# To ensure messages from proto files are created correctly, we need to
+# pass in dllexport_decl=<...> . Unfortunately, it doesn't appear that we
+# can just pass in dllexport_decl=ARROW_FLIGHT_EXPORT, as the visibility
+# macro won't be easily available to the generated proto file. See also
+# https://github.com/protocolbuffers/protobuf/issues/19422
+if cpp_compiler.get_id() == 'msvc'
+ proto_visibility = '__declspec(dllexport)'
+else
+ proto_visibility = '__attribute__((visibility("default")))'
+endif
+
flight_proto_files = custom_target(
'arrow-flight-proto-files',
input: [flight_proto_path / 'Flight.proto'],
output: ['Flight.pb.cc', 'Flight.pb.h'],
command: [
protoc,
'--proto_path=' + flight_proto_path,
- '--cpp_out=' + meson.current_build_dir(),
+ '--cpp_out=dllexport_decl=@0@:@1@'.format(
Review Comment:
But maybe it's fixed now?
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