[libc++][modules] Enable installation by default. (#90094)

This was suggested during the review of
https://github.com/llvm/llvm-project/pull/89413

This does not change the experimental state of modules.

libcxx/CMakeLists.txt

@@ -178,7 +178,7 @@ set(LIBCXX_LIBDIR_SUFFIX "${LLVM_LIBDIR_SUFFIX}" CACHE STRING
 option(LIBCXX_INSTALL_HEADERS "Install the libc++ headers." ON)
 option(LIBCXX_INSTALL_LIBRARY "Install the libc++ library." ON)
 option(LIBCXX_INSTALL_MODULES
-  "Install the libc++ C++20 module source files (experimental)." OFF
+  "Install the libc++ C++20 module source files (experimental)." ON
 )
 cmake_dependent_option(LIBCXX_INSTALL_STATIC_LIBRARY
   "Install the static libc++ library." ON

libcxx/cmake/caches/Generic-cxx20.cmake

@@ -1,3 +1,2 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "std=c++20" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-cxx23.cmake

@@ -1,3 +1,2 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "std=c++23" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-cxx26.cmake

@@ -1,3 +1,2 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "std=c++26" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-hardening-mode-extensive.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_HARDENING_MODE "extensive" CACHE STRING "")

libcxx/cmake/caches/Generic-no-exceptions.cmake

@@ -1,3 +1,2 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_EXCEPTIONS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_EXCEPTIONS OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-experimental.cmake

@@ -1,3 +1,2 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_TEST_PARAMS "enable_experimental=False" CACHE STRING "")
 set(LIBCXXABI_TEST_PARAMS "${LIBCXX_TEST_PARAMS}" CACHE STRING "")

libcxx/cmake/caches/Generic-no-filesystem.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_FILESYSTEM OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-localization.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_LOCALIZATION OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-random_device.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_RANDOM_DEVICE OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-threads.cmake

@@ -1,4 +1,3 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXXABI_ENABLE_THREADS OFF CACHE BOOL "")
 set(LIBCXX_ENABLE_MONOTONIC_CLOCK OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-unicode.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_UNICODE OFF CACHE BOOL "")

libcxx/cmake/caches/Generic-no-wide-characters.cmake

@@ -1,2 +1 @@
-set(LIBCXX_INSTALL_MODULES ON CACHE BOOL "") # TODO MODULES Remove when enabled automatically.
 set(LIBCXX_ENABLE_WIDE_CHARACTERS OFF CACHE BOOL "")

libcxx/docs/BuildingLibcxx.rst

@@ -208,7 +208,7 @@ libc++ specific options
 
 .. option:: LIBCXX_INSTALL_MODULES:BOOL
 
-  **Default**: ``OFF``
+  **Default**: ``ON``
 
   Toggle the installation of the experimental libc++ module sources.
 

libcxx/docs/ReleaseNotes/19.rst

@@ -149,3 +149,5 @@ Build System Changes
 
 - The Cmake variable ``LIBCXX_ENABLE_CLANG_TIDY`` has been removed. The build system has been changed
   to automatically detect the presence of ``clang-tidy`` and the required ``Clang`` libraries.
+
+- The CMake options ``LIBCXX_INSTALL_MODULES`` now defaults to ``ON``.