clang 17 warnings: `_LIBCPP_ENABLE_ASSERTIONS is deprecated`

[lucascolley]

Describe the bug
Building SciPy with clang 17 on macOS Sequoia 15.4 generates a wall of warnings like

[869/1447] Compiling C++ object subprojects/highs/src/libhighs.a.p/pdlp_CupdlpWrapper.cpp.o
In file included from ../subprojects/highs/src/pdlp/CupdlpWrapper.cpp:15:
In file included from ../subprojects/highs/src/pdlp/CupdlpWrapper.h:17:
In file included from /Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/algorithm:1821:
/Library/Developer/CommandLineTools/SDKs/MacOSX.sdk/usr/include/c++/v1/__config:48:6: warning: "_LIBCPP_ENABLE_ASSERTIONS is deprecated, please use _LIBCPP_HARDENING_MODE instead" [-W#warnings]
   48 | #    warning "_LIBCPP_ENABLE_ASSERTIONS is deprecated, please use _LIBCPP_HARDENING_MODE instead"
      |      ^
1 warning generated.

@andyfaff pointed out that https://github.com/mesonbuild/meson/blob/master/mesonbuild/compilers/cpp.py#L520C1-L532C57 looks relevant.

To Reproduce
https://github.com/scipy/scipy/blob/main/meson.build

Expected behavior
No warnings

system parameters
@andyfaff should be able to provide more system info if required

cc @thesamesam

[eli-schwartz]

#12683

For Clang, the situation is far more complicated:

• LLVM 18 uses a 'hardened mode' (https://libcxx.llvm.org/Hardening.html). There are several levels of severity available here. I've chosen _LIBCPP_HARDENING_MODE_DEBUG for now given it does the most but does not affect ABI, but we could change it to something more lightweight.

• LLVM 17 uses a similar approach to libstdc++ called '_LIBCPP_ENABLE_ASSERTIONS'

Note that LLVM 17 while in development had fully deprecated _LIBCPP_ENABLE_ASSERTIONS in favour of hardened, but changed its mind last-minute: https://discourse.llvm.org/t/rfc-hardening-in-libc/73925/4.

[danielcjacobs]

Not a build system person, but want to get rid of these warnings...what do I do? I've got clang 17.0.0, which ships with macOS Sequoia right now, and would rather not mess with my system compiler.

[thesamesam]

Workaround is to pass -Db_ndebug. For Apple Clang, I'm probably going to disable this entirely, or drop the legacy support there and only add it for new enough Apple Clang. The version mismatch between Apple Clang and upstream Clang makes things hard.

Can you show me clang --version output if you're hitting this? Thanks.

[danielcjacobs]

Can you show me clang --version output if you're hitting this?

I’ve got AppleClang 17.0.0

[andyfaff]

(dev3) 192-168-1-109:.github andrew$ clang --version
Apple clang version 17.0.0 (clang-1700.0.13.3)
Target: arm64-apple-darwin24.4.0
Thread model: posix
InstalledDir: /Applications/Xcode.app/Contents/Developer/Toolchains/XcodeDefault.xctoolchain/usr/bin