Warning C4251: class 'fmt::v8::file' needs to have dll-interface

[dalboris]

I get the following warning with fmt 8.1.1 (or latest commit) on MSCV 2019 (when compiling as a shared lib):

C:\Users\dalbo\vgc\third\fmt\include\fmt\os.h:414: warning: C4251: 'fmt::v8::ostream::file_': class 'fmt::v8::file' needs to have dll-interface to be used by clients of class 'fmt::v8::ostream'
C:\Users\dalbo\vgc\third\fmt\include\fmt/os.h(287): note: see declaration of 'fmt::v8::file'

The class file indeed isn't declared with FMT_API, although all its non-inline member functions are. The warning goes away if I add FMT_API to the whole class, and remove all the seperate per-function FMT_API.

Was there a good reason for not exporting the whole class, or should I make a PR exporting the whole class?

[dalboris]

Note: I don't have the warning with 7.1.3, but have the warning with 8.0.0, so something seems to have changed between those two versions causing the warning.

[dalboris]

Oh, I see what has changed: it's the class ostream which is exported with FMT_API since 8.0.0.

[dalboris]

This is the commit making the change, which apparently missed adding FMT_API to file too: 13e6529

[vitaut]

Could you submit a PR to add FMT_API where necessary?

[dalboris]

@vitaut : yes, done!