Warnings emitted by -Wdeprecated-redundant-constexpr-static-def

[giesmininkas]

Please provide the following information

libtorrent version (or branch): 2.0.10
platform/architecture: x86_64 GNU/Linux
compiler and compiler version: clang-19 w/ libc++-19

Clang check -Wdeprecated-redundant-constexpr-static-def, when compiling in C++17 or greater, emits many warnings, such as:

libtorrent-src/src/alert.cpp:72:36: warning: out-of-line definition of constexpr static data member is redundant in C++17 and is deprecated [-Wdeprecated-redundant-constexpr-static-def]
   72 |         constexpr alert_category_t alert::error_notification;
      |                                           ^

The warnings could be easily silenced by checking the __cplusplus preprocessor macro:

#if __cplusplus < 201703L
// define constexpr static data members
#endif

I can submit a patch if needed.

Thank you!

[arvidn]

Sure, a patch would be welcome. There's a risk, however, that __cplusplus won't be accurate enough. Also, I'm under the impression that you would need to rely in inline variables, by marking the declarations as inline in the header file. This is what I did in the master branch, which requires C++17 or later.