[libcxx-commits] [libcxx] [llvm] [libcxx] [ci] Add a test configuration with an incomplete sysroot (PR #107089)

[Martin Storsjö via libcxx-commits]

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@@ -715,6 +715,29 @@ mingw-dll-i686)
           -C "${MONOREPO_ROOT}/libcxx/cmake/caches/MinGW.cmake"
     check-runtimes
 ;;
+mingw-incomplete-sysroot)
+    # When bringing up a new cross compiler from scratch, we build
+    # libunwind/libcxx in a setup where the toolchain is incomplete and
+    # unable to perform the normal linker checks; this requires a few
+    # special cases in the CMake files.
+    #
+    # Building in an incomplete setup requires setting CMAKE_*_COMPILER_WORKS,
+    # as CMake fails to probe the compiler. This case also requires
+    # setting CMAKE_CXX_COMPILER_TARGET, as LLVM's heuristics for setting
+    # the triple fails when CMake hasn't been able to probe the environment.
+    # (This is what one has to do when building the initial libunwind/libcxx
+    # for a new toolchain.)
+    clean
+    generate-cmake \
+          -DCMAKE_C_COMPILER_WORKS=TRUE \
+          -DCMAKE_CXX_COMPILER_WORKS=TRUE \
+          -DCMAKE_C_COMPILER_TARGET=x86_64-w64-windows-gnu \
+          -DCMAKE_CXX_COMPILER_TARGET=x86_64-w64-windows-gnu \
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mstorsjo wrote:

I don’t consider this a bug that reasonably can be fixed.

At this stage, we can’t even link a trivial C application (the toolchain implicitly tries to link libunwind, which is yet to be built), so the cmake tests that normally deduce the target triple simply fall flat.

https://github.com/llvm/llvm-project/pull/107089