C++: Valgrind: map.InitializationErrorString(): jump or move depends on uninitialised value

[chrisse74]

Calling InitializationErrorString() on a Protobuf map leads to Valgrind reporting a 'jump or move depends on uninitialised value'.

Note: We get the same error when calling DebugString() instead of InitializationErrorString().

What version of protobuf and what language are you using?
Version: v29.2
Language: C++

What operating system (Linux, Windows, ...) and version?
Red Hat Enterprise Linux 9.5

What runtime / compiler are you using (e.g., python version or gcc version)
clang 19.1.6

What did you do?
Steps to reproduce the behavior:
We added debug symbols to the cmake release build to come up with the corresponding line numbers.

Sample Proto File:

syntax = "proto3";

option java_multiple_files = true;

package my.idl;

// This is a Map type documentation for StringMap
message StringMap
{
    map<string,string> string_map = 1;
}

Sample source file:

#include "MyTypesProto.grpc.pb.h"

int main(void)
{
    my::idl::StringMap stringMap;
    const std::string stringValue("test1234");
    stringMap.mutable_string_map()->insert({ stringValue, stringValue });

    stringMap.InitializationErrorString();

    google::protobuf::ShutdownProtobufLibrary();
}

What did you expect to see
No errors detected

What did you see instead?
See

• grpc_prot_valgrindDebugString_20250117.txt
• grpc_prot_valgrindInitializationErrorString_20250117.txt

Likely candidate is the is_repeated() call which is reported first in

protobuf/src/google/protobuf/descriptor.cc

Line 6646 in 2330983

if (proto.has_default_value() && result->is_repeated()) {

==1000== Conditional jump or move depends on uninitialised value(s)
==1000==    at 0x1BC369: google::protobuf::DescriptorBuilder::BuildFieldOrExtension(google::protobuf::FieldDescriptorProto const&, google::protobuf::Descriptor*, google::protobuf::FieldDescriptor*, bool, google::protobuf::internal::FlatAllocator&) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:6646)
==1000==    by 0x1B6D0E: BuildField (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:4420)
==1000==    by 0x1B6D0E: google::protobuf::DescriptorBuilder::BuildMessage(google::protobuf::DescriptorProto const&, google::protobuf::Descriptor const*, google::protobuf::Descriptor*, google::protobuf::internal::FlatAllocator&) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:6349)
==1000==    by 0x1B51CB: google::protobuf::DescriptorBuilder::BuildFileImpl(google::protobuf::FileDescriptorProto const&, google::protobuf::internal::FlatAllocator&) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:6129)
==1000==    by 0x1AFBF8: google::protobuf::DescriptorBuilder::BuildFile(google::protobuf::FileDescriptorProto const&) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:5893)
==1000==    by 0x1A585D: operator() (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:4750)
==1000==    by 0x1A585D: google::protobuf::DescriptorPool::BuildFileFromDatabase(google::protobuf::FileDescriptorProto const&, google::protobuf::DescriptorPool::DeferredValidation&) const (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:4755)
==1000==    by 0x1A3CC1: google::protobuf::DescriptorPool::TryFindFileInFallbackDatabase(std::__1::basic_string_view<char, std::__1::char_traits<char> >, google::protobuf::DescriptorPool::DeferredValidation&) const (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:2717)
==1000==    by 0x1A3BC5: google::protobuf::DescriptorPool::FindFileByName(std::__1::basic_string_view<char, std::__1::char_traits<char> >) const (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:2274)
==1000==    by 0x23520D: google::protobuf::(anonymous namespace)::AssignDescriptorsImpl(google::protobuf::internal::DescriptorTable const*, bool) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/generated_message_reflection.cc:3666)
==1000==    by 0x275DCB: operator() (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:168)
==1000==    by 0x275DCB: __invoke<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (sharecompiler.HEAD/linux/clang19el9/bin/../include/c++/v1/__type_traits/invoke.h:149)
==1000==    by 0x275DCB: invoke<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (sharecompiler.HEAD/linux/clang19el9/bin/../include/c++/v1/__functional/invoke.h:28)
==1000==    by 0x275DCB: void absl::lts_20240722::base_internal::CallOnceImpl<google::protobuf::Message::GetMetadataImpl(google::protobuf::internal::ClassDataFull const&)::$_0>(std::__1::atomic<unsigned int>*, absl::lts_20240722::base_internal::SchedulingMode, google::protobuf::Message::GetMetadataImpl(google::protobuf::internal::ClassDataFull const&)::$_0&&) (grpc-1.69.0/third_party/abseil-cpp/absl/base/call_once.h:182)
==1000==    by 0x2740EF: call_once<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (grpc-1.69.0/third_party/abseil-cpp/absl/base/call_once.h:216)
==1000==    by 0x2740EF: google::protobuf::Message::GetMetadataImpl(google::protobuf::internal::ClassDataFull const&) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167)
==1000==    by 0x1A391E: GetDescriptor (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.pb.h:10890)
==1000==    by 0x1A391E: descriptor (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.pb.h:10887)
==1000==    by 0x1A391E: google::protobuf::DescriptorPool::generated_pool() (grpc-1.69.0/third_party/protobuf/src/google/protobuf/descriptor.cc:2217)
==1000==    by 0x235126: MaybeInitializeLazyDescriptors (grpc-1.69.0/third_party/protobuf/src/google/protobuf/generated_message_reflection.cc:3693)
==1000==    by 0x235126: google::protobuf::internal::AssignDescriptorsOnceInnerCall(google::protobuf::internal::DescriptorTable const*) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/generated_message_reflection.cc:3731)
==1000==    by 0x275DCB: operator() (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:168)
==1000==    by 0x275DCB: __invoke<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (sharecompiler.HEAD/linux/clang19el9/bin/../include/c++/v1/__type_traits/invoke.h:149)
==1000==    by 0x275DCB: invoke<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (sharecompiler.HEAD/linux/clang19el9/bin/../include/c++/v1/__functional/invoke.h:28)
==1000==    by 0x275DCB: void absl::lts_20240722::base_internal::CallOnceImpl<google::protobuf::Message::GetMetadataImpl(google::protobuf::internal::ClassDataFull const&)::$_0>(std::__1::atomic<unsigned int>*, absl::lts_20240722::base_internal::SchedulingMode, google::protobuf::Message::GetMetadataImpl(google::protobuf::internal::ClassDataFull const&)::$_0&&) (grpc-1.69.0/third_party/abseil-cpp/absl/base/call_once.h:182)
==1000==    by 0x274092: call_once<(lambda at grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167:35)> (grpc-1.69.0/third_party/abseil-cpp/absl/base/call_once.h:216)
==1000==    by 0x274092: GetMetadataImpl (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:167)
==1000==    by 0x274092: google::protobuf::Message::GetMetadata() const (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:156)
==1000==    by 0x282FE0: GetDescriptor (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.h:362)
==1000==    by 0x282FE0: google::protobuf::internal::ReflectionOps::FindInitializationErrors(google::protobuf::Message const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, std::__1::vector<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >, std::__1::allocator<std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > > >*) (grpc-1.69.0/third_party/protobuf/src/google/protobuf/reflection_ops.cc:382)
==1000==    by 0x273E65: FindInitializationErrors (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:136)
==1000==    by 0x273E65: google::protobuf::Message::InitializationErrorString() const (grpc-1.69.0/third_party/protobuf/src/google/protobuf/message.cc:141)
==1000==    by 0x19BF94: main (main.cpp:9)

Anything else we should know about your project / environment
It affects us as gRPC 1.69.0 calls InitializationErrorString() in grpcpp/impl/generic_serialize.h (line 84)

[esrauchg]

I believe this must be a valgrind false positive.

is_repeated() is defined as:

inline bool FieldDescriptor::is_repeated() const {
  ABSL_DCHECK_EQ(is_repeated_, label() == LABEL_REPEATED);
  return is_repeated_;
}

Both label and is_repeated_ are always assigned above this line in the same function.

I suspect this is a false positive based on is_repeated_ is a bit field (the :1 syntax on the definition site), valgrind is confused because other adjacent bit fields are uninitialized, and then the valgrind path doesn't understand that uninitialized adjacent bits are not (in the C++ semantics) part of the comparison that is happening. But, I can't immediately find a reference to valgrind having this false positive case, so we may want to double check that.

[chrisse74]

The error goes away when a libprotobuf which was compiled without optimizations is used. (O1 does trigger it)