Apple Clang 14.0 lacks support for std::is_eq

[hebasto]

% cat test.cpp                   
#include <compare>

int main()
{
  double foo = -0.0;
  double bar = 0.0;
  return std::is_eq(foo <=> bar);
}
% clang++ -std=c++20 test.cpp        
test.cpp:7:15: error: no member named 'is_eq' in namespace 'std'
  return std::is_eq(foo <=> bar);
         ~~~~~^
1 error generated.
% clang -v                           
Apple clang version 14.0.0 (clang-1400.0.29.202)
Target: x86_64-apple-darwin21.6.0
Thread model: posix
InstalledDir: /Library/Developer/CommandLineTools/usr/bin

https://developer.apple.com/xcode/cpp/#c++20 didn't help much.

std::is_eq were added in #29242.

[fanquake]

We'll be dropping support for this compiler as soon as oss-fuzz rolls their Clang, and we bump our minimum.

[furszy]

Faced this too. Updating to 14.0.3 fixes the problem.

[hebasto]

Faced this too. Updating to 14.0.3 fixes the problem.

Well, that's actually means switching to the toolchain based on LLVM 15.

[hebasto]

@furszy

Faced this too. Updating to 14.0.3 fixes the problem.

Just to clarify, what macOS version did you update your clang on?

[furszy]

Ventura 13.1.

[hebasto]

Ventura 13.1.

Well. It seems Apple does not suggest any upgrade paths for Big Sur and Monterey, which are still supported platforms for Bitcoin Core 27.0.

[maflcko]

supported platforms

My understanding is that you can run Bitcoin Core on those platforms. However, compiling Bitcoin Core from source may not work out of the box.

If macOS does not offer an upgrade path for the system compiler, can you try to use a compiler provided by brew?

Another alternative would be to compile the compiler you need yourself.

[maflcko]

Faced this too. Updating to 14.0.3 fixes the problem.

Just to clarify the confusing versioning here, this corresponds to Xcode 14.3, llvm 15, and Apple Clang 14.0.3, according to https://en.wikipedia.org/wiki/Xcode#Xcode_11.0_-_14.x_%28since_SwiftUI_framework%29

[fanquake]

Yea. I think this can be closed with "use a compiler that better supports C++20". We still support the mentioned systems, and as far as I'm aware, installing and using a newer compiler would also work fine.

[Sjors]

I was going to suggest changing doc/dependencies.md to clarify the minimum clang version is 14.0.3 rather than 14.0, but #29165 bumps it to 15.0 anyway.

[maflcko]

I was going to suggest changing doc/dependencies.md to clarify the minimum clang version is 14.0.3 rather than 14.0, but #29165 bumps it to 15.0 anyway.

That would not be accurate. Clang 14 is indeed supported, see also https://godbolt.org/z/61seKv74b

The problem here is that Apple Clang 14.0.0 is apparently not based on llvm 14.0.0. I don't have further insights into Apples versioning nonsense, so I can't help here.

[Sjors]

I see, so Apple clang needs to be >=14.0.3, but for other operating systems 14.0 is fine.

[maflcko]

Anything left to be done here?