[CPP] Unable to pass SIzeVerifier to root verifier

[jtdavis777]

It looks like FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE was deprecated, the ability to call either of the following was broken:

flatbuffers::SizeVerifier verifier{ data, len };

verifier.VerifyBuffer<my_root_type>(); // compiler error

auto my_buffer = Getmy_root_type(data);

my_buffer->Verify(verifier); // compiler error

[jtdavis777]

these both fail with some flavor of

verifier.h:216:64: error: cannot convert 'flatbuffers::VerifierTemplate<true>' to 'flatbuffers::Verifier&' {aka 'flatbuffers::VerifierTemplate<false>&'}

[github-actions[bot]]

This issue is stale because it has been open 6 months with no activity. Please comment or label not-stale, or this will be closed in 14 days.

[sketch34]

I just encountered this as well.

[fergushenderson]

Thanks for reporting this.

And thanks to sketch34 for connecting this with issue #8274, which is how this hit my inbox. Sorry for the slow response, but until yesterday I wasn't aware of the issue.

A likely work-around is to continue to build with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE defined, and either be careful to avoid using SizeVerifier in header files, or be careful to ensure that all source files using flatbuffers get compiled with FLATBUFFERS_TRACK_VERIFIER_BUFFER_SIZE.

I have also uploaded a tentative fix to https://github.com/google/flatbuffers/commit/0af519ec861654cc1bccb27c67f08275a9dd72a6 but I haven't tested it much yet.

thejtshow and sketch34: perhaps you can try patching it in and seeing if it works for you?

[jtdavis777]

Sure, I can certainly take a look.

[fergushenderson]

I have now tested the patch that I posted earlier (0af519e), and it seems to work correctly for my use case, at least. So I have sent a pull request.

@dbaileychess