[C++] flatc doesn't create a working _generated.h file

[Fokson]

Attempted to follow the tutorial provided, using the monster.fbs schema and the newest compiled binary release of flatc ( 1.12 / 2.0 ).

The generated file is under half of the size of the example provided in the repo:

The monster_generated.h file created by flatc doesn't compile, giving the error "no matching function for call to 'MyGame::Sample::Monster::VerifyFieldMyGame::Sample::Vec3(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const', candidate expects 3 arguments, 2 provided"

Full log pasted below:
||=== Build: Debug in FlatBufferTest (compiler: GNU GCC Compiler) ===| FlatBufferTest\monster_generated.h||In member function 'bool MyGame::Sample::Monster::Verify(flatbuffers::Verifier&) const':| FlatBufferTest\monster_generated.h|173|error: no matching function for call to 'MyGame::Sample::Monster::VerifyField<MyGame::Sample::Vec3>(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|173|note: candidate expects 3 arguments, 2 provided| FlatBufferTest\monster_generated.h|174|error: no matching function for call to 'MyGame::Sample::Monster::VerifyField<int16_t>(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|174|note: candidate expects 3 arguments, 2 provided| FlatBufferTest\monster_generated.h|175|error: no matching function for call to 'MyGame::Sample::Monster::VerifyField<int16_t>(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|175|note: candidate expects 3 arguments, 2 provided| FlatBufferTest\monster_generated.h|180|error: no matching function for call to 'MyGame::Sample::Monster::VerifyField<int8_t>(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|180|note: candidate expects 3 arguments, 2 provided| FlatBufferTest\monster_generated.h|184|error: no matching function for call to 'MyGame::Sample::Monster::VerifyField<uint8_t>(flatbuffers::Verifier&, MyGame::Sample::Monster::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|184|note: candidate expects 3 arguments, 2 provided| FlatBufferTest\monster_generated.h||In member function 'bool MyGame::Sample::Weapon::Verify(flatbuffers::Verifier&) const':| FlatBufferTest\monster_generated.h|314|error: no matching function for call to 'MyGame::Sample::Weapon::VerifyField<int16_t>(flatbuffers::Verifier&, MyGame::Sample::Weapon::FlatBuffersVTableOffset) const'| .\flatbuffers\table.h|115|note: candidate: template<class T> bool flatbuffers::Table::VerifyField(const flatbuffers::Verifier&, flatbuffers::voffset_t, size_t) const| .\flatbuffers\table.h|115|note: template argument deduction/substitution failed:| FlatBufferTest\monster_generated.h|314|note: candidate expects 3 arguments, 2 provided| ||=== Build failed: 6 error(s), 0 warning(s) (0 minute(s), 1 second(s)) ===|

Others schemas besides the example fail similarly.

[dbaileychess]

It seems like there is a version mismatch between the generated code and the runtime libraries used. We recently added a third argument to the verifier that it looks like the generator you are using is not aware of.

You have to make sure the generated files and runtimes are at the same version.

[CasperN]

Maybe we can add a static assert for this?

[Fokson]

It seems like there is a version mismatch between the generated code and the runtime libraries used. We recently added a third argument to the verifier that it looks like the generator you are using is not aware of.

You have to make sure the generated files and runtimes are at the same version.

Would it be possible for you to put out a new version on the releases page? Seems the most recent one is from May 2021, which I suppose explains that.

[dbaileychess]

What release page are you referring too? I don't think this has to do with how we do releases.

Where did you get this?

the newest compiled binary release of flatc ( 1.12 / 2.0 ).

If you meant from here you also have to use the runtime libraries from those zip files. You cannot use the compiled binary from them and then use the library form HEAD on github.

[Fokson]

Yeah, from here. That's my bad, I was using the direct link from the tutorial page ( here ) to get the example .h file and using the latest available binary release, and didn't realize how outdated it was.

That being said, after downloading the source that matched the flatc binary from the releases page, the monster_generated.h file generated by flatc.exe still doesn't match the one provided in the sample files:

Despite the size difference, everything compiled and ran without errors this time. It would still be nice to see a more recent compiled binary in the releases section, but since the issue is effectively solved I'll close this issue. Thanks!

[dbaileychess]

Keeping this open to do an assert when we detect a mismatch.