flatbuffers_char_vec_t unknown

[tobiasBora]

Sorry if this is super basic, but I'm struggling to understand how to use this library. I used the following test.fbs:

table F { x:uint; }
table G { x:uint; y:uint; }

union Functions {
  F:F,
  G:G
}

and generated via flatcc -c, flatcc test.fbs and flatcc -w test.fbs the following files:

flatbuffers_common_builder.h  flatbuffers_common_reader.h  test_builder.h test_reader.h

Next, I created a minimal example C file test.c as:

#include <stdio.h>
#include <stdlib.h>
#include "test_builder.h"
#include "test_reader.h"
int main(int argc, char *argv[])
{
    // Initialize the builder
    flatcc_builder_t builder, *B;
    B = &builder;
    flatcc_builder_init(B);
    
    F_ref_t f_with_args = F_create(B, 42);
    return 0;
}

and tried to compile with:

$ gcc test.c *.h -o test -lflatccrt_d  -I /nix/store/24vvcm4sxnw8sj3jv9xjllifglx3lyn6-flatcc-0.6.1/include/flatcc

(note that I installed flatcc with nix as I'd like to avoid compiling it myself as it is already packaged)

but I get many errors:

─❯ LC_MESSAGES=C LANC=C gcc test.c *.h -o test -lflatccrt_d  -I /nix/store/24vvcm4sxnw8sj3jv9xjllifglx3lyn6-flatcc-0.6.1/include/flatcc                                                                                     ─╯
flatbuffers_common_builder.h:668:42: error: unknown type name ‘flatbuffers_char_vec_t’; did you mean ‘flatbuffers_char_vec_ref_t’?
  668 | __flatbuffers_build_scalar(flatbuffers_, flatbuffers_char, char)
      |                                          ^~~~~~~~~~~~~~~~
flatbuffers_common_builder.h:197:67: note: in definition of macro ‘__flatbuffers_build_vector’
  197 | static inline N ## _vec_ref_t N ## _vec_clone(NS ## builder_t *B, N ##_vec_t vec)\
      |                                                                   ^
flatbuffers_common_builder.h:668:1: note: in expansion of macro ‘__flatbuffers_build_scalar’
  668 | __flatbuffers_build_scalar(flatbuffers_, flatbuffers_char, char)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
flatbuffers_common_builder.h:668:42: error: unknown type name ‘flatbuffers_char_vec_t’; did you mean ‘flatbuffers_char_vec_ref_t’?
  668 | __flatbuffers_build_scalar(flatbuffers_, flatbuffers_char, char)
      |                                          ^~~~~~~~~~~~~~~~
flatbuffers_common_builder.h:199:67: note: in definition of macro ‘__flatbuffers_build_vector’
  199 | static inline N ## _vec_ref_t N ## _vec_slice(NS ## builder_t *B, N ##_vec_t vec, size_t index, size_t len)\
      |                                                                   ^
flatbuffers_common_builder.h:668:1: note: in expansion of macro ‘__flatbuffers_build_scalar’
  668 | __flatbuffers_build_scalar(flatbuffers_, flatbuffers_char, char)
      | ^~~~~~~~~~~~~~~~~~~~~~~~~~
flatbuffers_common_builder.h:669:42: error: unknown type name ‘flatbuffers_uint8_vec_t’; did you mean ‘flatbuffers_uint8_vec_ref_t’?
  669 | __flatbuffers_build_scalar(flatbuffers_, flatbuffers_uint8, uint8_t)
      |                                          ^~~~~~~~~~~~~~~~~
…

any idea what I did wrong?

[mikkelfj]

There errrors do not look like something you did wrong, more likely a version mismatch. Are you sure you are using the correct flatcc tool compared to the include files you are rerferencing?

FlatCC has been a bit slow with with official releases. It might be that you are generating code with a version that does not match the nix include header file, though I don't recall why vec_t should have changed to vec_ref_t for various types.

I general, the common files produced by flatcc depends on a few core types define in the include/flatcc directory, and there is likely some disagreement here.

I understand your point about not wanting to rebuild, but if you have CMake installed it is really easy to build. If you have ninja build it works out of the box otherwise you might have to call a setup script, dcoumented under build, to use make.

It takes like 2 seconds efter cloning and you have a local directory with all files, no external dependencies.

scripts/test.sh runs all tests after building automatically.

[mikkelfj]

The same issue has surfaced independently on discord flatbuffers channel under C.

https://discord.com/channels/656202785926152206/871499115928887306

[mikkelfj]

If you cannot or do not want to access the discord here is a summary of events so far:

The exact same char_vec_t error has shown. The user has successfully clone and build flatcc locally and compiled the monster example as a separate project using the setup.sh script listed early in the README, but get errors in their own project.

I have tried added the .fbs file causing problems to the monster test project and I get no errors.

My current suspicision is:

include/flatcc is installed as a system library with a package manager, but it is an old version.
When using include <flatcc/...> that system header gets used, and that might cause problems.

I cannot tell how to get your build to prefer one version over the other, but I do think flatcc should soon get a new release.