Always generate cmake config files

[hintonda]

Summary

Always generate and install cmake config files.

Currently, cmake config files are only generated and installed when CLANG_BUILD_STANDALONE set, which means config file will not be generated or installed when clang is built with llvm. This change removes that restriction.

[chapuni]

LGTM, but I haven't tested. I'll wait for 3rd opinion for several hours. :)

I thought it may be moved to an arbitrary subdirectory.

[jordan_rose]

I just get things to build with CMake, and I'm not involved with Clang so much these days. This is more about controlling what gets installed, which should be covered by someone else. ChrisB is spearheading the effort to ditch autoconf, so adding him instead.

[beanz]

LGTM.

[chapuni]

I am testing this with cmake-2.8.12. I remember some issues would be there.

[chapuni]

This change requires cmake-3.

With CMake-2.8.12.2,

CMake Error at /home/tnakamura/fio/ninja/llvm-project/clang/CMakeLists.txt:560 (export):
  export called with target "clangBasic" which requires target "LLVMCore"
  that is not in the export list.

  If the required target is not easy to reference in this call, consider
  using the APPEND option with multiple separate calls.

https://cmake.org/cmake/help/v3.0/release/3.0.0.html#commands

The export() command learned to work with multiple dependent export sets, thus allowing multiple packages to be built and exported from a single tree. The feature requires CMake to wait until the generation step to write the output file. This means one should not include() the generated targets file later during project configuration because it will not be available. Use Alias Targets instead. See policy CMP0024.

[hintonda]

Installed cmake 2.8.12 and was able to reproduce error.

I'll look into it, but I'm tempted to only support newer versions of cmake, and let older versions maintain current behavior.

[rnk]

I added this conditional check in r221415, with this message:

cmake: Only export targets in the standalone build

Trying to fix bots that didn't like the fact that I exported targets
that depended on LLVM without exporting targets from LLVM.

I assume this has already been addressed in LLVM? We now export targets there so we can depend on them in clang's exported targets file? If so, I'm happy to make this check simply conditional on the CMake version like you suggest.

I'm not actually a good reviewer for these kinds of things, I know very little about cmake package exports. =/ When I made this code change, I was just trying to hack the standalone build into shape. I haven't really used it since.

[hintonda]

• add back check for standalone and add cmake version

Verified that cmake 3.0.2 works, so I made the check for anything greater than 3.

[chapuni]

CMakeLists.txt

553–554

I'm afraid you mistook "conditionally skipped" as "worked".

Please change the condition, like

• 2.9
• 3.0.1 (Not sure any distros might take <3.0.2)
• EQUAL 3 OR GREATER 3
• NOT LESS 3

[hintonda]

Add support for cmake version 3, i.e., 3.0.0...

[hintonda]

Btw, I don't have commit access, so if you are happy with this change, could you commit it for me?

[chapuni]

Applied in r249935, thanks!

CMakeLists.txt

option(CLANG_INCLUDE_DOCS "Generate build targets for the Clang docs."
   ${LLVM_INCLUDE_DOCS})
 if( CLANG_INCLUDE_DOCS )
   add_subdirectory(docs)
 endif()
 
 set(CLANG_ORDER_FILE "" CACHE FILEPATH
   "Order file to use when compiling clang in order to improve startup time.")
 
-if (CLANG_BUILT_STANDALONE)
+if (CLANG_BUILT_STANDALONE OR CMAKE_VERSION VERSION_EQUAL 3 OR
+    CMAKE_VERSION VERSION_GREATER 3)
   # Generate a list of CMake library targets so that other CMake projects can
   # link against them. LLVM calls its version of this file LLVMExports.cmake, but
   # the usual CMake convention seems to be ${Project}Targets.cmake.
   set(CLANG_INSTALL_PACKAGE_DIR share/clang/cmake)
   set(clang_cmake_builddir "${CMAKE_BINARY_DIR}/${CLANG_INSTALL_PACKAGE_DIR}")
   get_property(CLANG_EXPORTS GLOBAL PROPERTY CLANG_EXPORTS)
   export(TARGETS ${CLANG_EXPORTS} FILE ${clang_cmake_builddir}/ClangTargets.cmake)