[libcxx-commits] [libcxx] e8605fb - [libc++] Disable automatic module scanning on ARM CI builders (#232947)

[via libcxx-commits]

Author: Mehdi Amini
Date: 2026-10-21T23:47:01+02:00
New Revision: e8605fba270516fe3715fe38e30904b3217d1bb1

URL: https://github.com/llvm/llvm-project/commit/e8605fba270516fe3715fe38e30904b3217d1bb1
DIFF: https://github.com/llvm/llvm-project/commit/e8605fba270516fe3715fe38e30904b3217d1bb1.diff

LOG: [libc++] Disable automatic module scanning on ARM CI builders (#232947)

The ARM Buildkite toolchains do not expose clang-scan-deps to CMake.
When CMP0155 enables automatic scanning for libc++abi C++23 sources,
these standalone runtimes builds fail with the scanner set to NOTFOUND.

Pass CMAKE_CXX_SCAN_FOR_MODULES=OFF in the eight ARM job invocations,
including the no-exceptions variants, until their toolchains provide a
matching scanner. Keep the other CI configurations on their defaults.

See the issue tracking upgrading the bots:
https://github.com/llvm/llvm-project/issues/232946

Assisted-by: Codex

Added: 
    

Modified: 
    libcxx/utils/ci/run-buildbot

Removed: 
    


################################################################################
diff  --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
index 3bfb5bb5fb02c3..1dbc1a385c8fc2 100755
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -717,12 +717,17 @@ apple-system|apple-system-hardened)
 ;;
 aarch64)
     clean
-    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake"
+    # The ARM builders' preinstalled toolchains do not provide a discoverable
+    # clang-scan-deps. Disable automatic module scanning for these jobs.
+    # See https://github.com/llvm/llvm-project/issues/232946.
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
     check-runtimes
 ;;
 aarch64-no-exceptions)
     clean
     generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/AArch64.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF \
                    -DLIBCXX_ENABLE_EXCEPTIONS=OFF \
                    -DLIBCXXABI_ENABLE_EXCEPTIONS=OFF
     check-runtimes
@@ -730,32 +735,38 @@ aarch64-no-exceptions)
 # Aka Armv8 32 bit
 armv8)
     clean
-    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Arm.cmake"
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Arm.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
     check-runtimes
 ;;
 armv8-no-exceptions)
     clean
-    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Thumb-no-exceptions.cmake"
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv8Thumb-no-exceptions.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
     check-runtimes
 ;;
 # Armv7 32 bit. One building Arm only one Thumb only code.
 armv7)
     clean
-    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Arm.cmake"
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Arm.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
     check-runtimes
 ;;
 armv7-no-exceptions)
     clean
-    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Thumb-no-exceptions.cmake"
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7Thumb-no-exceptions.cmake" \
+                   -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
     check-runtimes
 ;;
 armv7m-picolibc)
     test-armv7m-picolibc \
-        -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7M-picolibc.cmake"
+        -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7M-picolibc.cmake" \
+        -DCMAKE_CXX_SCAN_FOR_MODULES=OFF
 ;;
 armv7m-picolibc-no-exceptions)
     test-armv7m-picolibc \
         -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Armv7M-picolibc.cmake" \
+        -DCMAKE_CXX_SCAN_FOR_MODULES=OFF \
         -DLIBCXXABI_ENABLE_EXCEPTIONS=OFF \
         -DLIBCXXABI_ENABLE_STATIC_UNWINDER=OFF \
         -DLIBCXX_ENABLE_EXCEPTIONS=OFF \