Spurious "duplicate declaration" error with class members

[pitrou]

For one (and only one) of the classes in my project, I get a "duplicate declaration error" than I cannot explain:

Warning, treated as error:
/home/antoine/arrow/docs/source/cpp/api/builder.rst:31:Duplicate declaration.
Makefile:71: recipe for target 'html' failed
make: *** [html] Error 2

The directive is as follows:

.. doxygenclass:: arrow::BooleanBuilder
   :members:

If I remove the :members: flag, the error isn't emitted. How do I discover which member exactly is causing the duplicate declaration error, and why?

[vermeeren]

Could you check if your specific case is the same as #356? Perhaps parts of #405 (and linked issues from there) are also relevant.

If your issue is not related to the above I probably need more information.

[pitrou]

None of those two issues seem related. I'll try to see if I can single out the offending declaration (it would be nice if breathe said exactly what is duplicated).

[pitrou]

Ok, the two conflicting method declarations are the following (I'm omitting the implementations):

  /// \brief Append a sequence of elements in one shot, with a specified nullmap
  /// \param[in] values_begin InputIterator to the beginning of the values
  /// \param[in] values_end InputIterator pointing to the end of the values
  /// \param[in] valid_begin InputIterator with elements indication valid(1)
  ///  or null(0) values
  /// \return Status
  template <typename ValuesIter, typename ValidIter>
  typename std::enable_if<!std::is_pointer<ValidIter>::value, Status>::type AppendValues(
      ValuesIter values_begin, ValuesIter values_end, ValidIter valid_begin) {
     ...
  }

  /// \brief Append a sequence of elements in one shot, with a specified nullmap
  /// \param[in] values_begin InputIterator to the beginning of the values
  /// \param[in] values_end InputIterator pointing to the end of the values
  /// \param[in] valid_begin uint8_t* indication valid(1) or null(0) values.
  ///  nullptr indicates all values are valid.
  /// \return Status
  template <typename ValuesIter, typename ValidIter>
  typename std::enable_if<std::is_pointer<ValidIter>::value, Status>::type AppendValues(
      ValuesIter values_begin, ValuesIter values_end, ValidIter valid_begin) {
     ...
  }

This is the same template method implemented differently, depending on parameter type, using SFINAE.

[jakobandersen]

I'm quite sure this particular problem is a missing check in Sphinx. Please open an issue over there with a pointer to this issue, then I'll get around to it at some point.

[pitrou]

Ok, I opened sphinx-doc/sphinx#5755 in Sphinx.

[pitrou]

Note this is easily circumvented by removing one of the docstrings... Still, it is highly not obvious how to diagnose the issue and find the workaround.

[jakobandersen]

Thanks. I'll try to get the warning message improved as well (i.e., changing line https://github.com/sphinx-doc/sphinx/blob/master/sphinx/domains/cpp.py#L6459)

[pitrou]

I've got another case where I get a "duplicate declaration" with doxygen 1.8.14 (but not 1.8.13). It boils down to:

class BasicDecimal128 {
 public:
  /// \brief Create a BasicDecimal128 from the two's complement representation.
  constexpr BasicDecimal128(int64_t high, uint64_t low) noexcept
      : low_bits_(low), high_bits_(high) {}

  /// \brief Empty constructor creates a BasicDecimal128 with a value of 0.
  constexpr BasicDecimal128() noexcept : BasicDecimal128(0, 0) {}

 private:
  uint64_t low_bits_;
  int64_t high_bits_;
};

class Decimal128 : public BasicDecimal128 {
 public:
  using BasicDecimal128::BasicDecimal128;

  /// \brief Empty constructor wrapper over BasicDecimal128. This is required on some
  /// older compilers.
  constexpr Decimal128() noexcept : BasicDecimal128() {}
};

Together with:

.. doxygenclass:: arrow::Decimal128
   :project: arrow_cpp
   :members:

I get:

Warning, treated as error:
/home/antoine/arrow/docs/source/cpp/api/utilities.rst:25:Duplicate declaration, constexpr arrow::BasicDecimal128::BasicDecimal128()

This is with breathe 4.11.1 and sphinx 1.8.4+/d58f1018.

[pitrou]

Note it would also be nice to disable those "duplicate definition" warnings. There seem to be too many quirks with Doxygen-generated symbols.

[jakobandersen]

I think the new problem may be in the same family as #356.

[pitrou]

Not sure. I am not documenting the base class here (not in Sphinx, I mean). Also I have INLINE_INHERITED_MEMB = NO in the Doxyfile.

[vermeeren]

This might be fixed with #512, released in Breathe v4.17.0. Note that you also need Sphinx 3.x for recent Breathe versions. Could someone try and post results?

[Luthaf]

I still get a similar error related to two SFINAE methods with doxygen 1.8.20, sphinx 3.2.1 and breathe 4.21.0.

The code triggering the issue is reproduced below

template <typename T>
using SupportsMemoryIO = std::is_constructible<T, std::shared_ptr<MemoryBuffer>, File::Mode, File::Compression>;

class FormatFactory final {
public:
     // [...]

    /// Register a given `Format` in the factory if it supports memory IO
    template<class Format, enable_if_t<SupportsMemoryIO<Format>::value, int> = 0>
    void add_format() {
            // [...]
    }

    /// Register a given `Format` in the factory if it does not support memory IO
    template<class Format, enable_if_t<!SupportsMemoryIO<Format>::value, int> = 0>
    void add_format() {
            // [...]
    }
    // [...]
};

.. doxygenclass:: chemfiles::FormatFactory
    :members: