clangdev 17.0.0.rc2

[h-vetinari]

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[conda-forge-webservices]

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I considered the following status checks when analyzing this PR:

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[h-vetinari]

It's a bit concerning that the bump in GCC minimum revealed that apparently we've been using GCC's libstdcxx that must be somewhere in the MacOS image (presumably in the SDK?). Not sure if this was a recent change in llvm, but the fact that 17.0.0.rc1 passed (before llvm/llvm-project@5ddfea3 arrived with rc2) and then rc2 failed based on the detected libstdcxx version means we don't immediately know how far back this goes.

Failure looks like:

-- Performing Test LLVM_LIBSTDCXX_MIN
-- Performing Test LLVM_LIBSTDCXX_MIN - Failed
CMake Error at $PREFIX/lib/cmake/llvm/CheckCompilerVersion.cmake:88 (message):
  libstdc++ version must be at least 7.4.

Comes from here.

CC @conda-forge/clangdev

[h-vetinari]

Another aspect of libcxx dropping support for MacOS<10.13: just running clang is not compatible with 10.9 anymore:

+ clang++ -v -c mytest.cxx
clang version 17.0.0
Target: x86_64-apple-darwin20.6.0
Thread model: posix
InstalledDir: $PREFIX/bin
 (in-process)
 "$PREFIX/bin/clang-17" -cc1 -triple x86_64-apple-macosx10.9.0 -Wundef-prefix=TARGET_OS_OSX -Werror=undef-prefix -Wdeprecated-objc-isa-usage -Werror=deprecated-objc-isa-usage -emit-obj -mrelax-all -disable-free -clear-ast-before-backend -disable-llvm-verifier -discard-value-names -main-file-name mytest.cxx -mrelocation-model pic -pic-level 2 -mframe-pointer=all -ffp-contract=on -fno-rounding-math -funwind-tables=2 -faligned-alloc-unavailable -fcompatibility-qualified-id-block-type-checking -fvisibility-inlines-hidden-static-local-var -target-cpu core2 -tune-cpu generic -debugger-tuning=lldb -target-linker-version 609 -v -fcoverage-compilation-dir=/Users/runner/miniforge3/conda-bld/clang_packages_1691642825675/test_tmp -resource-dir $PREFIX/lib/clang/17 -isysroot /Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk -internal-isystem $PREFIX/include/c++/v1 -internal-isystem /Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/local/include -internal-isystem $PREFIX/lib/clang/17/include -internal-externc-isystem /Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include -fdeprecated-macro -fdebug-compilation-dir=/Users/runner/miniforge3/conda-bld/clang_packages_1691642825675/test_tmp -ferror-limit 19 -stack-protector 1 -fblocks -fencode-extended-block-signature -fregister-global-dtors-with-atexit -fgnuc-version=4.2.1 -fcxx-exceptions -fexceptions -fmax-type-align=16 -D__GCC_HAVE_DWARF2_CFI_ASM=1 -o mytest.o -x c++ mytest.cxx
clang -cc1 version 17.0.0 based upon LLVM 17.0.0 default target x86_64-apple-darwin20.6.0
ignoring nonexistent directory "/Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/local/include"
ignoring nonexistent directory "/Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/Library/Frameworks"
#include "..." search starts here:
#include <...> search starts here:
 $PREFIX/include/c++/v1
 $PREFIX/lib/clang/17/include
 /Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include
 /Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/System/Library/Frameworks (framework directory)
End of search list.
In file included from mytest.cxx:1:
In file included from $PREFIX/include/c++/v1/iostream:43:
In file included from $PREFIX/include/c++/v1/ios:221:
In file included from $PREFIX/include/c++/v1/__ios/fpos.h:14:
In file included from $PREFIX/include/c++/v1/iosfwd:106:
In file included from $PREFIX/include/c++/v1/__std_mbstate_t.h:14:
In file included from $PREFIX/include/c++/v1/__mbstate_t.h:45:
/Applications/Xcode_13.2.1.app/Contents/Developer/Platforms/MacOSX.platform/Developer/SDKs/MacOSX10.9.sdk/usr/include/sys/_types/_mbstate_t.h:31:9: error: unknown type name '__darwin_mbstate_t'
   31 | typedef __darwin_mbstate_t mbstate_t;
      |         ^
1 error generated.

This happens with libcxx 17 here, but I don't actually understand how that can get pulled into the test env at all, as it has an explicit constraint for >= 10.13, and we were running on 10.9 here so far.