[runtimes] Always define cxx_shared, cxx_static & other targets

However, mark them as EXCLUDE_FROM_ALL when we don't want to build them.
Simply declaring the targets should be of no harm, and it allows other
projects to mention these targets regardless of whether they end up
being built or not.

This patch basically moves the definition of e.g. cxx_shared out of
the `if (LIBCXX_ENABLE_SHARED)` and instead marks it as EXCLUDE_FROM_ALL
conditionally on whether LIBCXX_ENABLE_SHARED is passed. It then does the
same for libunwind and libc++abi targets.

This is a reapplication of 79ee034, which was reverted in a353909
because it broke the TSAN and the Fuchsia builds.

Resolves llvm#77654

Differential Revision: https://reviews.llvm.org/D134221

libcxx/cmake/caches/AIX.cmake

@@ -16,3 +16,10 @@ set(LIBCXX_CXX_ABI libcxxabi CACHE STRING "")
 set(LIBUNWIND_ENABLE_SHARED ON CACHE BOOL "")
 set(LIBUNWIND_ENABLE_STATIC OFF CACHE BOOL "")
 set(LIBCXX_ABI_DEFINES "_LIBCPP_ABI_IOS_ALLOW_ARBITRARY_FILL_VALUE" CACHE STRING "")
+
+# On AIX, both shared and static libraries are archived. As a result, both the static and the shared targets end
+# up with a `.a` suffix, which conflict. To workaround that, we set a different output name for the static
+# libraries, which we never actually build anyway. For more information, see https://gitlab.kitware.com/cmake/cmake/-/issues/19494.
+set(LIBCXX_STATIC_OUTPUT_NAME "c++-static" CACHE STRING "")
+set(LIBCXXABI_STATIC_OUTPUT_NAME "c++abi-static" CACHE STRING "")
+set(LIBUNWIND_STATIC_OUTPUT_NAME "unwind-static" CACHE STRING "")

libcxx/cmake/caches/Armv7M-picolibc.cmake

@@ -39,3 +39,14 @@ set(LIBUNWIND_IS_BAREMETAL ON CACHE BOOL "")
 set(LIBUNWIND_REMEMBER_HEAP_ALLOC ON CACHE BOOL "")
 set(LIBUNWIND_USE_COMPILER_RT ON CACHE BOOL "")
 find_program(QEMU_SYSTEM_ARM qemu-system-arm REQUIRED)
+
+# On embedded platforms that don't support shared library targets, CMake implicitly changes shared
+# library targets to be static library targets. This results in duplicate definitions of the static
+# library targets even though we might not ever build the shared library target, which breaks the
+# build. To work around this, we change the output name of the  shared library target so that it
+# can't conflict with the static library target.
+#
+# This is tracked by https://gitlab.kitware.com/cmake/cmake/-/issues/25759.
+set(LIBCXX_SHARED_OUTPUT_NAME "c++-shared" CACHE STRING "")
+set(LIBCXXABI_SHARED_OUTPUT_NAME "c++abi-shared" CACHE STRING "")
+set(LIBUNWIND_SHARED_OUTPUT_NAME "unwind-shared" CACHE STRING "")

libcxx/src/CMakeLists.txt

@@ -143,10 +143,6 @@ if (LIBCXX_ENABLE_NEW_DELETE_DEFINITIONS)
     )
 endif()
 
-if(NOT LIBCXX_INSTALL_LIBRARY)
-  set(exclude_from_all EXCLUDE_FROM_ALL)
-endif()
-
 if (APPLE AND LLVM_USE_SANITIZER)
   if (("${LLVM_USE_SANITIZER}" STREQUAL "Address") OR
       ("${LLVM_USE_SANITIZER}" STREQUAL "Address;Undefined") OR
@@ -177,13 +173,13 @@ split_list(LIBCXX_COMPILE_FLAGS)
 split_list(LIBCXX_LINK_FLAGS)
 
 # Build the shared library.
-if (LIBCXX_ENABLE_SHARED)
-  add_library(cxx_shared SHARED ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
+  add_library(cxx_shared SHARED ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
   target_include_directories(cxx_shared PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
   target_link_libraries(cxx_shared PUBLIC cxx-headers libcxx-libc-shared
                                    PRIVATE ${LIBCXX_LIBRARIES})
   set_target_properties(cxx_shared
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBCXX_ENABLE_SHARED}>,FALSE,TRUE>"
       COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
       LINK_FLAGS    "${LIBCXX_LINK_FLAGS}"
       OUTPUT_NAME   "${LIBCXX_SHARED_OUTPUT_NAME}"
@@ -251,7 +247,10 @@ if (LIBCXX_ENABLE_SHARED)
     )
   endif()
 
+if (LIBCXX_ENABLE_SHARED)
   list(APPEND LIBCXX_BUILD_TARGETS "cxx_shared")
+endif()
+
   if(WIN32 AND NOT MINGW AND NOT "${CMAKE_HOST_SYSTEM_NAME}" STREQUAL "Windows")
     # Since we most likely do not have a mt.exe replacement, disable the
     # manifest bundling.  This allows a normal cmake invocation to pass which
@@ -264,19 +263,18 @@ if (LIBCXX_ENABLE_SHARED)
                             APPEND_STRING PROPERTY LINK_FLAGS " -Xlinker /MANIFEST:NO")
     endif()
   endif()
-endif()
 
 set(CMAKE_STATIC_LIBRARY_PREFIX "lib")
 
 # Build the static library.
-if (LIBCXX_ENABLE_STATIC)
-  add_library(cxx_static STATIC ${exclude_from_all} ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
+  add_library(cxx_static STATIC ${LIBCXX_SOURCES} ${LIBCXX_HEADERS})
   target_include_directories(cxx_static PRIVATE ${CMAKE_CURRENT_SOURCE_DIR})
   target_link_libraries(cxx_static PUBLIC cxx-headers libcxx-libc-static
                                    PRIVATE ${LIBCXX_LIBRARIES}
                                    PRIVATE libcxx-abi-static)
   set_target_properties(cxx_static
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBCXX_ENABLE_STATIC}>,FALSE,TRUE>"
       COMPILE_FLAGS "${LIBCXX_COMPILE_FLAGS}"
       LINK_FLAGS    "${LIBCXX_LINK_FLAGS}"
       OUTPUT_NAME   "${LIBCXX_STATIC_OUTPUT_NAME}"
@@ -299,16 +297,18 @@ if (LIBCXX_ENABLE_STATIC)
     target_compile_definitions(cxx_static PRIVATE _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS=)
   endif()
 
-  list(APPEND LIBCXX_BUILD_TARGETS "cxx_static")
+  if (LIBCXX_ENABLE_STATIC)
+    list(APPEND LIBCXX_BUILD_TARGETS "cxx_static")
+  endif()
   # Attempt to merge the libc++.a archive and the ABI library archive into one.
   if (LIBCXX_STATICALLY_LINK_ABI_IN_STATIC_LIBRARY)
     target_link_libraries(cxx_static PRIVATE libcxx-abi-static-objects)
   endif()
-endif()
 
 # Add a meta-target for both libraries.
 add_custom_target(cxx DEPENDS ${LIBCXX_BUILD_TARGETS})
 
+# Build the experimental static library
 set(LIBCXX_EXPERIMENTAL_SOURCES
   experimental/keep.cpp
   )

libcxxabi/src/CMakeLists.txt

@@ -184,10 +184,10 @@ if (CMAKE_POSITION_INDEPENDENT_CODE OR NOT DEFINED CMAKE_POSITION_INDEPENDENT_CO
 endif()
 target_compile_options(cxxabi_shared_objects PRIVATE "${LIBCXXABI_ADDITIONAL_COMPILE_FLAGS}")
 
-if (LIBCXXABI_ENABLE_SHARED)
   add_library(cxxabi_shared SHARED)
   set_target_properties(cxxabi_shared
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBCXXABI_ENABLE_SHARED}>,FALSE,TRUE>"
       LINK_FLAGS "${LIBCXXABI_LINK_FLAGS}"
       OUTPUT_NAME "${LIBCXXABI_SHARED_OUTPUT_NAME}"
       SOVERSION "1"
@@ -208,10 +208,12 @@ if (LIBCXXABI_ENABLE_SHARED)
     PUBLIC cxxabi_shared_objects
     PRIVATE ${LIBCXXABI_LIBRARIES})
 
+if (LIBCXXABI_ENABLE_SHARED)
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_shared")
-  if (LIBCXXABI_INSTALL_SHARED_LIBRARY)
-    list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_shared")
-  endif()
+endif()
+if (LIBCXXABI_INSTALL_SHARED_LIBRARY)
+  list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_shared")
+endif()
 
   add_library(cxxabi-reexports INTERFACE)
   function(export_symbols file)
@@ -252,7 +254,6 @@ if (LIBCXXABI_ENABLE_SHARED)
       reexport_symbols("${CMAKE_CURRENT_SOURCE_DIR}/../lib/personality-v0.exp")
     endif()
   endif()
-endif()
 
 # Build the static library.
 add_library(cxxabi_static_objects OBJECT EXCLUDE_FROM_ALL ${LIBCXXABI_SOURCES} ${LIBCXXABI_HEADERS})
@@ -292,24 +293,25 @@ if(LIBCXXABI_HERMETIC_STATIC_LIBRARY)
       _LIBCPP_DISABLE_VISIBILITY_ANNOTATIONS=)
 endif()
 
-if (LIBCXXABI_ENABLE_STATIC)
   add_library(cxxabi_static STATIC)
   if (LIBCXXABI_USE_LLVM_UNWINDER AND NOT LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_STATIC_LIBRARY)
     target_link_libraries(cxxabi_static PUBLIC unwind_static)
   endif()
   set_target_properties(cxxabi_static
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBCXXABI_ENABLE_STATIC}>,FALSE,TRUE>"
       LINK_FLAGS "${LIBCXXABI_LINK_FLAGS}"
       OUTPUT_NAME "${LIBCXXABI_STATIC_OUTPUT_NAME}"
     )
   target_link_libraries(cxxabi_static
     PUBLIC cxxabi_static_objects
     PRIVATE ${LIBCXXABI_STATIC_LIBRARIES} ${LIBCXXABI_LIBRARIES})
 
+if (LIBCXXABI_ENABLE_STATIC)
   list(APPEND LIBCXXABI_BUILD_TARGETS "cxxabi_static")
-  if (LIBCXXABI_INSTALL_STATIC_LIBRARY)
-    list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_static")
-  endif()
+endif()
+if (LIBCXXABI_INSTALL_STATIC_LIBRARY)
+  list(APPEND LIBCXXABI_INSTALL_TARGETS "cxxabi_static")
 endif()
 
 # Add a meta-target for both libraries.

libunwind/src/CMakeLists.txt

@@ -153,22 +153,23 @@ if (CMAKE_POSITION_INDEPENDENT_CODE OR NOT DEFINED CMAKE_POSITION_INDEPENDENT_CO
   set_target_properties(unwind_shared_objects PROPERTIES POSITION_INDEPENDENT_CODE ON) # must set manually because it's an object library
 endif()
 
-if (LIBUNWIND_ENABLE_SHARED)
   add_library(unwind_shared SHARED)
   target_link_libraries(unwind_shared PUBLIC unwind_shared_objects)
   set_target_properties(unwind_shared
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBUNWIND_ENABLE_SHARED}>,FALSE,TRUE>"
       LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
       LINKER_LANGUAGE C
       OUTPUT_NAME "${LIBUNWIND_SHARED_OUTPUT_NAME}"
       VERSION     "${LIBUNWIND_LIBRARY_VERSION}"
       SOVERSION   "1"
   )
 
+if (LIBUNWIND_ENABLE_SHARED)
   list(APPEND LIBUNWIND_BUILD_TARGETS "unwind_shared")
-  if (LIBUNWIND_INSTALL_SHARED_LIBRARY)
-    list(APPEND LIBUNWIND_INSTALL_TARGETS "unwind_shared")
-  endif()
+endif()
+if (LIBUNWIND_INSTALL_SHARED_LIBRARY)
+  list(APPEND LIBUNWIND_INSTALL_TARGETS "unwind_shared")
 endif()
 
 # Build the static library.
@@ -199,20 +200,21 @@ if(LIBUNWIND_HIDE_SYMBOLS)
   target_compile_definitions(unwind_static_objects PRIVATE _LIBUNWIND_HIDE_SYMBOLS)
 endif()
 
-if (LIBUNWIND_ENABLE_STATIC)
   add_library(unwind_static STATIC)
   target_link_libraries(unwind_static PUBLIC unwind_static_objects)
   set_target_properties(unwind_static
     PROPERTIES
+      EXCLUDE_FROM_ALL "$<IF:$<BOOL:${LIBUNWIND_ENABLE_STATIC}>,FALSE,TRUE>"
       LINK_FLAGS "${LIBUNWIND_LINK_FLAGS}"
       LINKER_LANGUAGE C
       OUTPUT_NAME "${LIBUNWIND_STATIC_OUTPUT_NAME}"
   )
 
+if (LIBUNWIND_ENABLE_STATIC)
   list(APPEND LIBUNWIND_BUILD_TARGETS "unwind_static")
-  if (LIBUNWIND_INSTALL_STATIC_LIBRARY)
-    list(APPEND LIBUNWIND_INSTALL_TARGETS "unwind_static")
-  endif()
+endif()
+if (LIBUNWIND_INSTALL_STATIC_LIBRARY)
+  list(APPEND LIBUNWIND_INSTALL_TARGETS "unwind_static")
 endif()
 
 # Add a meta-target for both libraries.