[llvm] [libcxx] [libc++][CI] Tests the no RTTI configuration. (PR #65518)

[Mark de Wever via llvm-commits]

https://github.com/mordante updated https://github.com/llvm/llvm-project/pull/65518

>From 2da01301d82d6de069a8f0f04a9642a19228bab1 Mon Sep 17 00:00:00 2001
From: Mark de Wever <koraq at xs4all.nl>
Date: Wed, 6 Sep 2023 20:59:55 +0200
Subject: [PATCH] [libc++][CI] Tests the no RTTI configuration.

There are a few drive-by fixes:
- Since the combination RTTI disabled and exceptions enabled do not
  work, this combination is prohibited.
- A small NFC in any fixing clang-tidy.

The code in the Buildkite configuration is prepared for using the std
module. There are more fixes needed for that configuration which will be
done in a separate commit.
---
 .github/workflows/libcxx-build-and-test.yaml |  1 +
 libcxx/CMakeLists.txt                        | 11 ++++++++++-
 libcxx/cmake/caches/Generic-no-rtti.cmake    |  4 ++++
 libcxx/docs/BuildingLibcxx.rst               |  1 +
 libcxx/utils/ci/run-buildbot                 |  5 +++++
 5 files changed, 21 insertions(+), 1 deletion(-)
 create mode 100644 libcxx/cmake/caches/Generic-no-rtti.cmake

diff --git a/.github/workflows/libcxx-build-and-test.yaml b/.github/workflows/libcxx-build-and-test.yaml
index 268e1033387dcb..370cf830a60cf8 100644
--- a/.github/workflows/libcxx-build-and-test.yaml
+++ b/.github/workflows/libcxx-build-and-test.yaml
@@ -160,6 +160,7 @@ jobs:
           'generic-no-tzdb',
           'generic-no-unicode',
           'generic-no-wide-characters',
+          'generic-no-rtti',
           'generic-static',
           'generic-with_llvm_unwinder',
           # TODO Find a better place for the benchmark and bootstrapping builds to live. They're either very expensive
diff --git a/libcxx/CMakeLists.txt b/libcxx/CMakeLists.txt
index 31fc9cec1c57f2..a8a942cfe43bdf 100644
--- a/libcxx/CMakeLists.txt
+++ b/libcxx/CMakeLists.txt
@@ -284,7 +284,9 @@ endif()
 
 # Feature options -------------------------------------------------------------
 option(LIBCXX_ENABLE_EXCEPTIONS "Use exceptions." ON)
-option(LIBCXX_ENABLE_RTTI "Use run time type information." ON)
+option(LIBCXX_ENABLE_RTTI
+  "Use runtime type information.
+   This option may only be set to OFF when LIBCXX_ENABLE_EXCEPTIONS=OFF." ON)
 option(LIBCXX_ENABLE_THREADS "Build libc++ with support for threads." ON)
 option(LIBCXX_ENABLE_MONOTONIC_CLOCK
   "Build libc++ with support for a monotonic clock.
@@ -374,6 +376,13 @@ if (LIBCXX_HAS_PTHREAD_API)
   endif()
 endif()
 
+if (NOT LIBCXX_ENABLE_RTTI AND LIBCXX_ENABLE_EXCEPTIONS)
+  message(FATAL_ERROR "Libc++ cannot be built with exceptions enabled but RTTI"
+	                  " disabled, since that configuration is broken. See"
+					  " https://github.com/llvm/llvm-project/issues/66117"
+					  " for details.")
+endif()
+
 # Ensure LLVM_USE_SANITIZER is not specified when LIBCXX_GENERATE_COVERAGE
 # is ON.
 if (LLVM_USE_SANITIZER AND LIBCXX_GENERATE_COVERAGE)
diff --git a/libcxx/cmake/caches/Generic-no-rtti.cmake b/libcxx/cmake/caches/Generic-no-rtti.cmake
new file mode 100644
index 00000000000000..c62ddcec90149b
--- /dev/null
+++ b/libcxx/cmake/caches/Generic-no-rtti.cmake
@@ -0,0 +1,4 @@
+set(LIBCXX_ENABLE_RTTI OFF CACHE BOOL "")
+set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
+set(LIBCXXABI_ENABLE_RTTI OFF CACHE BOOL "")
+set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
diff --git a/libcxx/docs/BuildingLibcxx.rst b/libcxx/docs/BuildingLibcxx.rst
index 2cee97c03ced08..0b4d4205286512 100644
--- a/libcxx/docs/BuildingLibcxx.rst
+++ b/libcxx/docs/BuildingLibcxx.rst
@@ -369,6 +369,7 @@ libc++ Feature Options
   **Default**: ``ON``
 
   Build libc++ with run time type information.
+  This option may only be set to OFF when LIBCXX_ENABLE_EXCEPTIONS=OFF.
 
 .. option:: LIBCXX_INCLUDE_TESTS:BOOL
 
diff --git a/libcxx/utils/ci/run-buildbot b/libcxx/utils/ci/run-buildbot
index 445b1becee0c2a..ee890fb7669962 100755
--- a/libcxx/utils/ci/run-buildbot
+++ b/libcxx/utils/ci/run-buildbot
@@ -472,6 +472,11 @@ generic-no-exceptions)
     check-runtimes
     check-abi-list
 ;;
+generic-no-rtti)
+    clean
+    generate-cmake -C "${MONOREPO_ROOT}/libcxx/cmake/caches/Generic-no-rtti.cmake"
+    check-runtimes
+;;
 #
 # Other miscellaneous jobs
 #