[libc++] Simplify how we define the linker script for libc++

[ldionne]

Summary

Trying to be generic didn't work properly because we had to special-case
some interface libraries that we didn't want in the linker script. Instead,
only look at the ABI and the unwinding libraries explicitly.

This should solve the issue reported by @dim in [1].

[1]: https://discourse.llvm.org/t/15-0-0-rc1-has-been-tagged/64174/22

[ldionne]

CI passes and IMO this is cleaner than what we had before, and there is a chance of fixing the issues that folks were seeing w/ the release, so I'll ship this.

[dim]

Unfortunately it doesn't really change anything on the FreeBSD build side. It still shows similar output when I put some messages in there:

DBG: LIBCXX_DEFAULT_ABI_LIBRARY="libcxxrt"
DBG: LIBCXX_CXX_ABI="libcxxrt"
-- LIBCXX_CXX_ABI_INCLUDE_PATHS not set, using /usr/include/c++/v1
-- Looking for cxxabi.h in /usr/include/c++/v1 - found
-- Looking for unwind.h in /usr/include/c++/v1 - found
-- Looking for unwind-arm.h in /usr/include/c++/v1 - found
-- Looking for unwind-itanium.h in /usr/include/c++/v1 - found
DBG: link_libraries="-l$<IF:$<BOOL:$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>>,$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>,$<TARGET_PROPERTY:libcxx-abi-shared,OUTPUT_NAME>>"
DBG: linker_script="INPUT($<TARGET_SONAME_FILE_NAME:cxx_shared> -l$<IF:$<BOOL:$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>>,$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>,$<TARGET_PROPERTY:libcxx-abi-shared,OUTPUT_NAME>>)"

and the resulting linker script is still:

INPUT(libc++.so.1 -l)

This is again likely because libcxx-abi-shared is empty, as the default ABI library is libcxxrt, not libcxxabi.

[dim]

So I've been trying again with the following diff applied on top of this one:

diff --git a/libcxx/src/CMakeLists.txt b/libcxx/src/CMakeLists.txt
index 9abf548abbb9..d6769e4a3e64 100644
--- a/libcxx/src/CMakeLists.txt
+++ b/libcxx/src/CMakeLists.txt
@@ -244,7 +244,9 @@ if (LIBCXX_ENABLE_SHARED)

     set(imported_libname "$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>")
     set(output_name "$<TARGET_PROPERTY:libcxx-abi-shared,OUTPUT_NAME>")
-    string(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}$<IF:$<BOOL:${imported_libname}>,${imported_libname},${output_name}>")
+    # NOTE: We cannot use the LOCATION target property, since that is forbidden by the CMP0026 policy.
+    set(target_file "$<TARGET_FILE:libcxx-abi-shared>")
+    string(APPEND link_libraries "$<IF:$<BOOL:${imported_libname}>,${CMAKE_LINK_LIBRARY_FLAG}${imported_libname},$<IF:$<BOOL:${output_name}>,${CMAKE_LINK_LIBRARY_FLAG}${output_name},${target_file}>>")

     # TODO: Move to the same approach as above for the unwind library
     if (LIBCXXABI_USE_LLVM_UNWINDER)

E.g. what this does is fall-back to $<TARGET_FILE:libcxx-abi-shared>, if both IMPORTED_LIBNAME and OUTPUT_NAME are unset, which turns out to be the case if LIBCXX_CXX_ABI=libcxxrt. That causes the linker script to look like:

INPUT(libc++.so.1 /usr/lib/libcxxrt.so)

Which works up to a point, but then it turns out that during the runtime builds for some reason the line target_compile_definitions(libcxx-abi-headers INTERFACE "-DLIBCXXRT") (from libcxx/cmake/Modules/HandleLibCXXABI.cmake) isn't picked up. E.g. the whole of libc++ is then compiled _without_ the -DLIBCXXRT define necessary for supporting libcxxrt, and at the end the build still fails, but now with:

FAILED: bin/llvm-tblgen
: && /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/clang++ -fPIC -fno-semantic-interposition -fvisibility-inlines-hidden -Werror=date-time -Werror=unguarded-availability-new -Wall -Wextra -Wno-unused-parameter -Wwrite-strings -Wcast-qual -Wmissing-field-initializers -pedantic -Wno-long-long -Wc++98-compat-extra-semi -Wimplicit-fallthrough -Wcovered-switch-default -Wno-noexcept-type -Wnon-virtual-dtor -Wdelete-non-virtual-dtor -Wsuggest-override -Wno-comment -Wstring-conversion -Wmisleading-indentation -fdiagnostics-color -ffunction-sections -fdata-sections -O3 -DNDEBUG -Wl,--color-diagnostics    -Wl,-z,origin  -Wl,--gc-sections utils/TableGen/CMakeFiles/llvm-tblgen.dir/AsmMatcherEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/AsmWriterEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/AsmWriterInst.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/Attributes.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CallingConvEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeEmitterGen.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenDAGPatterns.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenHwModes.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenInstruction.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenMapTable.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenRegisters.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenSchedule.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CodeGenTarget.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DAGISelEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DAGISelMatcherEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DAGISelMatcherGen.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DAGISelMatcherOpt.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DAGISelMatcher.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DecoderEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DFAEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DFAPacketizerEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DirectiveEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DisassemblerEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/DXILEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/ExegesisEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/FastISelEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/GICombinerEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/GlobalISelEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/InfoByHwMode.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/InstrInfoEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/InstrDocsEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/IntrinsicEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/OptEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/OptParserEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/OptRSTEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/PredicateExpander.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/PseudoLoweringEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CompressInstEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/RegisterBankEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/RegisterInfoEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/SDNodeProperties.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/SearchableTableEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/SubtargetEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/SubtargetFeatureInfo.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/TableGen.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/Types.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/VarLenCodeEmitterGen.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86DisassemblerTables.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86EVEX2VEXTablesEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86FoldTablesEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86MnemonicTables.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86ModRMFilters.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/X86RecognizableInstr.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/WebAssemblyDisassemblerEmitter.cpp.o utils/TableGen/CMakeFiles/llvm-tblgen.dir/CTagsEmitter.cpp.o -o bin/llvm-tblgen  -Wl,-rpath,"\$ORIGIN/../lib"  lib/libLLVMSupport.a  lib/libLLVMTableGen.a  -lpthread  lib/libLLVMTableGenGlobalISel.a  lib/libLLVMTableGen.a  lib/libLLVMSupport.a  -lrt  -lexecinfo  -lpthread  -lm  /usr/lib/libz.so  /usr/lib/libtinfo.so  lib/libLLVMDemangle.a && :
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to __cxa_uncaught_exceptions
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::logic_error::~logic_error()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::logic_error::what() const
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to typeinfo for std::logic_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to typeinfo for std::overflow_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::overflow_error::~overflow_error()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::overflow_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::logic_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::runtime_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to typeinfo for std::length_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::length_error::~length_error()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to typeinfo for std::out_of_range
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::out_of_range::~out_of_range()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::length_error
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::out_of_range
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to vtable for std::invalid_argument
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to typeinfo for std::invalid_argument
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::invalid_argument::~invalid_argument()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::runtime_error::~runtime_error()
ld: error: /home/dim/llvm/15.0.0/rc1/Phase1/Release/llvmCore-15.0.0-rc1.install/usr/local/bin/../lib/x86_64-unknown-freebsd12.3/libc++.so.1: undefined reference to std::runtime_error::what() const
ld: error: too many errors emitted, stopping now (use -error-limit=0 to see all errors)
clang-15: error: linker command failed with exit code 1 (use -v to see invocation)

The errors mean it was assuming it was being linked against libcxxabi instead.

At this point I'm inclined to just do the test builds with LIBCXX_CXX_ABI forced to libcxxabi, as the runtimes seem to be pretty much broken for anything other than libcxxabi. :-)

[ldionne]

In D131037#3704812, @dim wrote:

So I've been trying again with the following diff applied on top of this one:

[...]

At this point I'm inclined to just do the test builds with LIBCXX_CXX_ABI forced to libcxxabi, as the runtimes seem to be pretty much broken for anything other than libcxxabi. :-)

Thanks for digging deeper here. However, I'll admit that I am not willing to keep shooting in the dark with random fixes. Instead, can you please pick up D128084 so we can start testing on FreeBSD? Most of the work has been done already, it just needs a bit of polishing that will be much easier to do with access to a FreeBSD machine locally.

I think this is an excellent example of what I've been saying with respect to untested platforms meaning they are not supported. I really want to provide proper support for FreeBSD, but it's literally impossible to do so if we don't have CI for that platform. We should have CI that builds on FreeBSD against the system libcxxrt ABI library like you do in the releases and none of this release-time churn would happen.

libcxx/cmake/Modules/DefineLinkerScript.cmake

-# This function defines a linker script in place of the symlink traditionally
-# created for shared libraries.
-#
-# More specifically, this function goes through the PUBLIC and INTERFACE
-# library dependencies of <target> and gathers them into a linker script,
-# such that those libraries are linked against when the shared library for
-# <target> is linked against.
-#
-# Arguments:
-#   <target>: A target representing a shared library. A linker script will be
-#             created in place of that target's TARGET_LINKER_FILE, which is
-#             the symlink pointing to the actual shared library (usually
-#             libFoo.so pointing to libFoo.so.1, which itself points to
-#             libFoo.so.1.0).
-
-function(define_linker_script target)
-  if (NOT TARGET "${target}")
-    message(FATAL_ERROR "The provided target '${target}' is not actually a target.")
-  endif()
-
-  get_target_property(target_type "${target}" TYPE)
-  if (NOT "${target_type}" STREQUAL "SHARED_LIBRARY")
-    message(FATAL_ERROR "The provided target '${target}' is not a shared library (its type is '${target_type}').")
-  endif()
-
-  set(symlink "$<TARGET_LINKER_FILE:${target}>")
-  set(soname "$<TARGET_SONAME_FILE_NAME:${target}>")
-
-  get_target_property(interface_libs "${target}" INTERFACE_LINK_LIBRARIES)
-
-  set(link_libraries)
-  if (interface_libs)
-    foreach(lib IN LISTS interface_libs)
-      if ("${lib}" MATCHES "cxx-headers|ParallelSTL")
-        continue()
-      endif()
-      # If ${lib} is not a target, we use a dummy target which we know will
-      # have an OUTPUT_NAME property so that CMake doesn't fail when evaluating
-      # the non-selected branch of the `IF`. It doesn't matter what it evaluates
-      # to because it's not selected, but it must not cause an error.
-      # See https://gitlab.kitware.com/cmake/cmake/-/issues/21045.
-      set(output_name_tgt "$<IF:$<TARGET_EXISTS:${lib}>,${lib},${target}>")
-      set(libname "$<IF:$<TARGET_EXISTS:${lib}>,$<TARGET_PROPERTY:${output_name_tgt},OUTPUT_NAME>,${lib}>")
-      list(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}${libname}")
-    endforeach()
-  endif()
-  string(REPLACE ";" " " link_libraries "${link_libraries}")
-
-  set(linker_script "INPUT(${soname} ${link_libraries})")
-  add_custom_command(TARGET "${target}" POST_BUILD
-    COMMAND "${CMAKE_COMMAND}" -E remove "${symlink}"
-    COMMAND "${CMAKE_COMMAND}" -E echo "${linker_script}" > "${symlink}"
-    COMMENT "Generating linker script: '${linker_script}' as file ${symlink}"
-    VERBATIM
-  )
-endfunction()

libcxx/src/CMakeLists.txt

PROPERTIES
       OUTPUT_NAME   "c++"
       VERSION       "${LIBCXX_LIBRARY_VERSION}"
       SOVERSION     "${LIBCXX_ABI_VERSION}"
       DEFINE_SYMBOL ""
   )
   cxx_add_common_build_flags(cxx_shared)
   cxx_set_common_defines(cxx_shared)
 
-  # Link against LLVM libunwind
-  # Note that we do need to link against libunwind directly to ensure that the correct
-  # dependencies are recorded when creating a linker script.
-  # TODO: Look into modifying the linker script creation to recursively consider interface libraries
-  if (LIBCXXABI_USE_LLVM_UNWINDER)
-    if (LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY)
-      # libunwind is already included in libc++abi
-    elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
-      target_link_libraries(cxx_shared PUBLIC unwind_shared)
-    else()
-      target_link_libraries(cxx_shared PUBLIC unwind)
-    endif()
-  endif()
-
   # Link against libc++abi
   if (LIBCXX_STATICALLY_LINK_ABI_IN_SHARED_LIBRARY)
     target_link_libraries(cxx_shared PRIVATE libcxx-abi-shared-objects)
   else()
     target_link_libraries(cxx_shared PUBLIC libcxx-abi-shared)
   endif()
 
   # Maybe re-export symbols from libc++abi
target_link_libraries(cxx_shared PRIVATE
       "-Wl,-force_symbols_not_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/../lib/notweak.exp"
       "-Wl,-force_symbols_weak_list,${CMAKE_CURRENT_SOURCE_DIR}/../lib/weak.exp")
 
     target_link_libraries(cxx_shared PRIVATE $<TARGET_NAME_IF_EXISTS:cxxabi-reexports>)
   endif()
 
   # Generate a linker script in place of a libc++.so symlink.
   if (LIBCXX_ENABLE_ABI_LINKER_SCRIPT)
-      include(DefineLinkerScript)
-      define_linker_script(cxx_shared)
+    set(link_libraries)
+
+    set(imported_libname "$<TARGET_PROPERTY:libcxx-abi-shared,IMPORTED_LIBNAME>")
+    set(output_name "$<TARGET_PROPERTY:libcxx-abi-shared,OUTPUT_NAME>")
+    string(APPEND link_libraries "${CMAKE_LINK_LIBRARY_FLAG}$<IF:$<BOOL:${imported_libname}>,${imported_libname},${output_name}>")
+
+    # TODO: Move to the same approach as above for the unwind library
+    if (LIBCXXABI_USE_LLVM_UNWINDER)
+      if (LIBCXXABI_STATICALLY_LINK_UNWINDER_IN_SHARED_LIBRARY)
+        # libunwind is already included in libc++abi
+      elseif (TARGET unwind_shared OR HAVE_LIBUNWIND)
+        string(APPEND link_libraries " ${CMAKE_LINK_LIBRARY_FLAG}$<TARGET_PROPERTY:unwind_shared,OUTPUT_NAME>")
+      else()
+        string(APPEND link_libraries " ${CMAKE_LINK_LIBRARY_FLAG}unwind")
+      endif()
+    endif()
+
+    set(linker_script "INPUT($<TARGET_SONAME_FILE_NAME:cxx_shared> ${link_libraries})")
+    add_custom_command(TARGET cxx_shared POST_BUILD
+      COMMAND "${CMAKE_COMMAND}" -E remove "$<TARGET_LINKER_FILE:cxx_shared>"
+      COMMAND "${CMAKE_COMMAND}" -E echo "${linker_script}" > "$<TARGET_LINKER_FILE:cxx_shared>"
+      COMMENT "Generating linker script: '${linker_script}' as file $<TARGET_LINKER_FILE:cxx_shared>"
+      VERBATIM
+    )
   endif()
 
   list(APPEND LIBCXX_BUILD_TARGETS "cxx_shared")
   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
     # will attempt to use the manifest tool to generate the bundled manifest
     set_target_properties(cxx_shared PROPERTIES