undefined reference to `google::protobuf::internal::SerializeInternal'

[vervaekejonathan]

Compiling protocolbuffers 3.5.1 for Cortex-M4 processor.

using the following commands:

 ./configure  --host=arm-none-eabi --build=x86_64-unknown-linux-gnu --prefix=/usr --exec-prefix=/usr --sysconfdir=/etc --localstatedir=/var --program-prefix= --disable-gtk-doc --disable-doc --disable-docs --disable-documentation --with-xmlto=no --with-fop=no --disable-dependency-tracking --disable-ipv6 --disable-debug --enable-static --enable-shared --with-protoc=/usr/local/bin/protoc CFLAGS=--specs=rdimon.specs CXXFLAGS=--specs=rdimon.specs CC=/github/arm-none-eabi_gcc_6.3.1/arm-none-eabi/bin/arm-none-eabi-gcc CXX=/github/arm-none-eabi_gcc_6.3.1/arm-none-eabi/bin/arm-none-eabi-g++ --without-thread-safety

cd src/

make CFLAGS=--specs=rdimon.specs CXXFLAGS='--specs=rdimon.specs -DLANG_CX11 -DPROTOBUF_WITHOUT_THREAD_SAFETY  -mthumb -mcpu=cortex-m4 -ffunction-sections  -mlong-calls -mcpu=cortex-m4 -Os' CC=/github/arm-none-eabi_gcc_6.3.1/arm-none-eabi/bin/arm-none-eabi-gcc CXX=/github/arm-none-eabi_gcc_6.3.1/arm-none-eabi/bin/arm-none-eabi-g++ libprotobuf-lite.la 

note: you need arm-none-eabi_gcc_6.3.1

This builds with after minor modifications to the Mutex library (replace the implementation with empty functions)

When linking the created libprotobuf-lite.a with my project, the linker complains about the following:

 Error		undefined reference to `google::protobuf::internal::SerializeInternal(unsigned char const*, google::protobuf::internal::FieldMetadata const*, int, google::protobuf::io::CodedOutputStream*)'	XXXX	XXXX\Debug\message_lite.cc	1
 Error		undefined reference to `google::protobuf::internal::SerializeInternalToArray(unsigned char const*, google::protobuf::internal::FieldMetadata const*, int, bool, unsigned char*)'	XXXX	XXXX\Debug\message_lite.cc	1

[acozzette]

Those two functions are defined in src/google/protobuf/generated_message_util.cc, so I'm not sure why they would be missing. Could you check if they were included in libprotobuf-lite.a? Another thing to note is that SerializeInternal and SerializeInternalToArray are only used for the experimental table-driven serialization, which is not being used yet. So if you just want a quick fix to get things building, you could probably delete those functions and their call sites without breaking any real functionality.

[vervaekejonathan]

It seems the function is included in the library (same for SerializeInternalToArray):

/github/arm-none-eabi_gcc_6.3.1/arm-none-eabi/arm-none-eabi/bin/readelf -a libprotobuf-lite.a  | ag SerializeInternal
Relocation section '.rel.text._ZN6google8protobuf8internal17SerializeInternalEPKhPKNS1_13FieldMetadataElPNS0_2io17CodedOutputStreamE' at offset 0x62f0 contains 71 entries:
Relocation section '.rel.ARM.exidx.text._ZN6google8protobuf8internal17SerializeInternalEPKhPKNS1_13FieldMetadataElPNS0_2io17CodedOutputStreamE' at offset 0x6528 contains 2 entries:
Unwind table index '.ARM.exidx.text._ZN6google8protobuf8internal17SerializeInternalEPKhPKNS1_13FieldMetadataElPNS0_2io17CodedOutputStreamE' at offset 0x1f74 contains 1 entries:
0x0 <_ZN6google8protobuf8internal17SerializeInternalEPKhPKNS1_13FieldMetadataElPNS0_2io17CodedOutputStreamE>: 0x8034afb0

[vervaekejonathan]

I've found the problem, the declaration and definition of SerializeInternal and SerializeInternalToArray is different:

LIBPROTOBUF_EXPORT void SerializeInternal(const uint8* base, const FieldMetadata* table,
                       int num_fields, ::google::protobuf::io::CodedOutputStream* output);

void SerializeInternal(const uint8* base,
                       const FieldMetadata* field_metadata_table,
                       int32 num_fields,
                       ::google::protobuf::io::CodedOutputStream* output) {

should be

LIBPROTOBUF_EXPORT void SerializeInternal(const uint8* base, const FieldMetadata* table,
                       int32 num_fields, ::google::protobuf::io::CodedOutputStream* output);

When changing int to int32 in the declaration, the linker can find the definition and my program compiles!

[acozzette]

Nice, I'm glad to hear you got it working! If you're interested you can send us a pull request with that fix and I'll merge it.

[vervaekejonathan]

here you go!
#4815

[acozzette]

Thanks!