WARNING: Invalid C++ declaration: Expected end of definition.

[ReenigneArcher]

I'm looking to add Doxygen to Sunshine. It's a project that I took over maintenance on, I'm not the original developer, and my c++ skills are not great (one of the reasons I actually want to use breathe to help me learn the c++).

I'm wondering if someone here can help with some errors that I cannot make sense of when I add one particular file.

Since, the project is open source, I'll just add links here. I'm not sure if there's an issue with the c++ code or just something with the Doxyfile configuation. Any support would be greatly appreciated!

PR that adds Doxygen + breathe: LizardByte/Sunshine#1004
Doxyfile: https://github.com/LizardByte/Sunshine/blob/docs-add-doxygen/docs/Doxyfile
File that is generating these specific errors: https://github.com/LizardByte/Sunshine/blob/docs-add-doxygen/src/utility.h
Read the docs log: https://readthedocs.org/projects/sunshinestream/builds/19692680/

The error messages when I add this file:

/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Invalid C++ declaration: Expected end of definition. [error at 26]
  template<class T> optional, T > > >
  --------------------------^
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_3_01std_1_1optional_00_01T_01_4_01_4_01_4_1ab9a85ff499bd63b2ceb38a779cc6ff8c".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_3_01std_1_1optional_00_01T_01_4_01_4_01_4_1ab9a85ff499bd63b2ceb38a779cc6ff8c".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_3_01std_1_1optional_00_01T_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_3_01std_1_1optional_00_01T_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Invalid C++ declaration: Expected end of definition. [error at 51]
  template<class T> enable_if_t< is_pointer_v< T > > >
  ---------------------------------------------------^
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Duplicate C++ declaration, also defined at source/utility:4.
Declaration is '.. cpp:member:: static constexpr std::nullptr_t value   = nullptr'.
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01is__pointer__v_3_01T_01_4_01_4_01_4_1a4c9328ac1d486f22b8a1c511636d517c".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01is__pointer__v_3_01T_01_4_01_4_01_4_1a4c9328ac1d486f22b8a1c511636d517c".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01is__pointer__v_3_01T_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01is__pointer__v_3_01T_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Invalid C++ declaration: Expected end of definition. [error at 39]
  template<class T> is_same_v< T, bool > > >
  ---------------------------------------^
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Duplicate C++ declaration, also defined at source/utility:4.
Declaration is '.. cpp:member:: static constexpr bool value   = false'.
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01std_1_1is__same__v_3_01T_00_01bool_01_4_01_4_01_4_1afb76e0d92027a244e3282ecb74225b77".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01std_1_1is__same__v_3_01T_00_01bool_01_4_01_4_01_4_1afb76e0d92027a244e3282ecb74225b77".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01std_1_1is__same__v_3_01T_00_01bool_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1____false__v_3_01T_00_01std_1_1enable__if__t_3_01std_1_1is__same__v_3_01T_00_01bool_01_4_01_4_01_4".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Duplicate C++ declaration, also defined at source/utility:4.
Declaration is '.. cpp:struct:: template<class... Ts> overloaded : public Ts'.
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Invalid C++ declaration: Expected end of definition. [error at 26]
  template<class T> optional, T >)> >
  --------------------------^
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff_1ad0ebaf9a7c97b01349abbd86326058c3".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff_1ad0ebaf9a7c97b01349abbd86326058c3".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff_1a5c041306efd7fedaa18da4ff2b533b36".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff_1a5c041306efd7fedaa18da4ff2b533b36".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01_9_07instantiation__ob3db11a8d516b4032d3ecc2a0dd246ff".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Invalid C++ declaration: Expected end of definition. [error at 26]
  template<class T> optional, T > > >
  --------------------------^
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Duplicate C++ declaration, also defined at source/utility:4.
Declaration is '.. cpp:function:: static inline T little (T x)'.
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b_1ae8817feb6527a6acb52306b74232465d".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b_1ae8817feb6527a6acb52306b74232465d".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:4: WARNING: Duplicate C++ declaration, also defined at source/utility:4.
Declaration is '.. cpp:function:: static inline T big (T x)'.
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b_1aa28b8ea25d203be16ca2f504b92f4735".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b_1aa28b8ea25d203be16ca2f504b92f4735".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: CRITICAL: Duplicate ID: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b".
/home/docs/checkouts/readthedocs.org/user_builds/sunshinestream/checkouts/1004/docs/source/source/utility.rst:2: WARNING: Duplicate explicit target name: "structutil_1_1endian_1_1endian__helper_3_01T_00_01std_1_1enable__if__t_3_01instantiation__of__v_0fea619a60fca1c46381aa29a9b23f8b".