why can I not access std::stop_token?

[patrick99e99]

I am using emcc with -std=c++23 and am getting:

emulator.cpp:13:8: error: no type named 'stop_token' in namespace 'std'
   13 |   std::stop_token token;
      |   ~~~~~^

[sbc100]

It looks like stop_token in marked as experimental in the LLVM 18 version of libc++. See

emscripten/system/lib/libcxx/include/__config

Lines 507 to 514 in 2e84cfd

	// Incomplete features get their own specific disabling flags. This makes it
	// easier to grep for target specific flags once the feature is complete.
	# if !defined(_LIBCPP_ENABLE_EXPERIMENTAL) && !defined(_LIBCPP_BUILDING_LIBRARY)
	# define _LIBCPP_HAS_NO_INCOMPLETE_PSTL
	# define _LIBCPP_HAS_NO_EXPERIMENTAL_STOP_TOKEN
	# define _LIBCPP_HAS_NO_INCOMPLETE_TZDB
	# define _LIBCPP_HAS_NO_EXPERIMENTAL_SYNCSTREAM
	# endif

.

Looks like you can enable it at your own risk by defining _LIBCPP_ENABLE_EXPERIMENTAL.

[sbc100]

It looks like this is also still experimental in the LLVM 19 version of libc++ so even once we fix #22909 this will still be an issue.