rtpsw commented on PR #14207:
URL: https://github.com/apache/arrow/pull/14207#issuecomment-1257874379
It turns out template instantiations and attributes (in this case,
visibility) do not work together nicely. When I try adding code like
`template<> class ARROW_EXPORT ArrayVectorSourceNodeOptions`, I get compiler
errors like:
```
/mnt/user1/tscontract/github/rtpsw/arrow/cpp/src/arrow/compute/exec/options.h:113:31:
error: using typedef-name ‘using ArrayVectorSourceNodeOptions = class
arrow::compute::SchemaSourceNodeOptions<std::function<arrow::Iterator<std::shared_ptr<std::vector<std::shared_ptr<arrow::Array>
> > >()> >’ after ‘class’
113 | template<> class ARROW_EXPORT ArrayVectorSourceNodeOptions;
| ^~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
and when I try adding code like `template<> class ARROW_EXPORT
SchemaSourceNodeOptions<ArrayVectorIteratorMaker>`, I get compiler warnings
like:
```
/mnt/user1/tscontract/github/rtpsw/arrow/cpp/src/arrow/compute/exec/options.h:113:31:
warning: attributes ignored on template instantiation [-Wattributes]
113 | template<> class ARROW_EXPORT
SchemaSourceNodeOptions<ArrayVectorIteratorMaker>;
|
^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
```
So, both tries do not work, at least with my compiler. There seems to be a
[proposal documenting this
limitation](https://www.open-std.org/jtc1/sc22/wg21/docs/papers/2017/p0537r0.html),
but I'm not sure what its status is.
In the commit I just made, I opted instead to explicitly define and export
non-template symbols.
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