error C3861: 'GenericWriteVariableUnsigned': identifier not found

[jeanga]

When I naively compile using bond, I always get the following error message:

7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\encoding.h(53,5): error C3861: 'GenericWriteVariableUnsigned': identifier not found (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\encoding.h(53,5): message : 'GenericWriteVariableUnsigned': function was not declared in the template definition context and can be found only via argument-dependent lookup in the instantiation context (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(814): message : see reference to function template instantiation 'void bond::WriteVariableUnsigned<Flashback::Details::Bond::Stream,T>(Buffer &,T)' being compiled
7>        with
7>        [
7>            T=uint32_t,
7>            Buffer=Flashback::Details::Bond::Stream
7>        ] (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(892): message : see reference to function template instantiation 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::Write<uint32_t>(const T &)' being compiled
7>        with
7>        [
7>            T=uint32_t
7>        ] (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(892): message : see reference to function template instantiation 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::Write<uint32_t>(const T &)' being compiled
7>        with
7>        [
7>            T=uint32_t
7>        ] (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(717): message : see reference to function template instantiation 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::LengthBegin<Flashback::Details::Bond::Stream>(T &)' being compiled
7>        with
7>        [
7>            T=Flashback::Details::Bond::Stream
7>        ] (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(717): message : see reference to function template instantiation 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::LengthBegin<Flashback::Details::Bond::Stream>(T &)' being compiled
7>        with
7>        [
7>            T=Flashback::Details::Bond::Stream
7>        ] (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\protocol\compact_binary.h(714): message : while compiling class template member function 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::WriteStructBegin(const bond::Metadata &,bool)' (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>S:\vcpkg\installed\x64-windows-static\include\bond\core\transforms.h(73): message : see reference to function template instantiation 'void bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>::WriteStructBegin(const bond::Metadata &,bool)' being compiled (compiling source file F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp)
7>F:\Projects\Flashback\tests\FlashTest\bond_dictionary.cpp(153): message : see reference to class template instantiation 'bond::CompactBinaryWriter<Flashback::Details::Bond::Stream>' being compiled

This seems to be because GenericWriteVariableUnsigned appears used before it is defined (encoding.h, line 45):

template<typename Buffer, typename T>
inline
typename boost::disable_if<implements_varint_write<Buffer, T> >::type
WriteVariableUnsigned(Buffer& output, T value)
{
    BOOST_STATIC_ASSERT(std::is_unsigned<T>::value);

    // Use generic WriteVariableUnsigned
    GenericWriteVariableUnsigned(output, value);
}


template<typename Buffer, typename T>
BOND_NO_INLINE
void GenericWriteVariableUnsigned(Buffer& output, T value)
{
....
}

I always 'fix' this compile error with a forward declaration of GenericWriteVariableUnsigned:

template<typename Buffer, typename T>
BOND_NO_INLINE
void GenericWriteVariableUnsigned(Buffer& output, T value);

template<typename Buffer, typename T>
inline
typename boost::disable_if<implements_varint_write<Buffer, T> >::type
WriteVariableUnsigned(Buffer& output, T value)
{
...
}

Please let me know if this is an issue from my side or if this 'fix' should be included in future releases of bond.

Best,
Jean

[chwarr]

Yes, a forward declaration makes sense. I've created PR #1118 [c++] Forward declare GenericWriteVariableUnsigned. Take a look if you have a moment, please.

My hypothesis for why you are seeing this is that your Flashback::Details::Bond::Stream does not have a WriteVariableUnsigned(T value) member function. Is that the case? (A Bond stream doesn't need to have such a member function, but if one exists, it will be used over GenericWriteVariableUnsigned.)

If you add a definition of WriteVariableUnsigned(T value) to your Flashback::Details::Bond::Stream does this error go away?

My guess is that we're not seeing this in Bond itself because bond::OutputBuffer has such a member function, so the WriteVariableUnsigned specialization that invokes GenericWriteVariableUnsigned is not used.