Generated code for Protobuf failing to build

[sqcsabbey]

I'm getting the error message:

Error: Field 'c' requires exactly one annotation to declare its native type, which cannot be Void. dart:ffi Structs and Unions cannot have regular Dart fields.

For the ffigen'd code:

/// A union for storing all possible Protobuf values. Note that owner is
/// responsible for memory management of object types.
typedef GPBGenericValue = UnnamedUnion7;

/// A union for storing all possible Protobuf values. Note that owner is
/// responsible for memory management of object types.
final class UnnamedUnion7 extends ffi.Union {
  external BOOL1 c;

  @ffi.Int()
  external int valueInt32;

  @ffi.Int()
  external int valueInt64;

  @ffi.Int()
  external int valueUInt32;

  @ffi.Int()
  external int valueUInt64;

  @ffi.Float()
  external double valueFloat;

  @ffi.Double()
  external double valueDouble;

  external ffi.Pointer<ffi.Int> valueData;

  external ffi.Pointer<ffi.Int> valueString;

  external ffi.Pointer<ffi.Int> valueMessage;

  @ffi.Int()
  external int valueEnum;
}

I'm not using Protobuf directly, but my Podfile.lock uses Protobuf (3.23.0), and I'm trying to get this working against Dart 3.0.0 and using ffigen 8.0.2 (whatever was generated was working for me before upgrading to Dart 3 and ffigen 8).

Any tips to help me resolve this?

Thanks!

[dcharkes]

@sqcsabbey thanks for the report.

What is the definition of BOOL1?

(We added bool support in #310.)

[sqcsabbey]

@dcharkes, thanks for responding to my report so quickly. Here's BOOL1's definition:

/// Verifies that a given value can be represented by an enum type.
typedef BOOL1 = ffi.NativeFunction<
    ffi.NativeFunction<ffi.Int Function()> Function(ffi.Pointer<ffi.Int>)>;

[dcharkes]

We can't have a NativeFunction<...> as a field of a Union, we can only have a Pointer<NativeFunction<...>>. What is the definition of c in C/C++ that causes this to be generated?

[sqcsabbey]

Here's the header file for it, with this typedef on line 42:

/**
 * Verifies that a given value can be represented by an enum type.
 * */
typedef BOOL (*GPBEnumValidationFunc)(int32_t);

Edit: that's an Obj-C header, and from the matching comments in the ffigen'd code and this header file, I believe this is what's being used.

[dcharkes]

/**
 * Verifies that a given value can be represented by an enum type.
 * */
typedef BOOL (*GPBEnumValidationFunc)(int32_t);

This is using BOOL and defining GPBEnumValidationFunc.

I'd hope the typedef would simply be this from https://developer.apple.com/documentation/objectivec/bool:

typedef bool BOOL;

Can you check you have got the right include paths and there are no errors on the FFIgen output?

[sqcsabbey]

I did have an error in the FFIgen output; the iOS Foundation header file wasn't found; adding this to my ffigen.yaml got it working for iOS:

compiler-opts:
  - '-F/Applications/Xcode.app/Contents/Developer/Platforms/iPhoneOS.platform/Developer/SDKs/iPhoneOS.sdk/System/Library/Frameworks'
  - '-mios-version-min=13.0'

[dcharkes]

Alright 👌

Please let us know if you have further issues.