[PATCH] D62172: [cmake] Add custom command to touch archives so ninja won't rebuild them.

[Don Hinton via Phabricator via llvm-commits]

hintonda updated this revision to Diff 200517.
hintonda added a comment.

- Restrict to Darwin > 15.6.0.  Ninja version not available, so will add code to get that and hide all of this under a new variable in the next version of this patch.


Repository:
  rG LLVM Github Monorepo

CHANGES SINCE LAST ACTION
  https://reviews.llvm.org/D62172/new/

https://reviews.llvm.org/D62172

Files:
  llvm/cmake/modules/AddLLVM.cmake


Index: llvm/cmake/modules/AddLLVM.cmake
===================================================================
--- llvm/cmake/modules/AddLLVM.cmake
+++ llvm/cmake/modules/AddLLVM.cmake
@@ -596,6 +596,21 @@
     llvm_externalize_debuginfo(${name})
     llvm_codesign(${name} ENTITLEMENTS ${ARG_ENTITLEMENTS})
   endif()
+  # clang and newer versions of ninja use high-resolutions timestamps,
+  # but older versions of libtool on Darwin don't, so the archive will
+  # often get an older timestamp than the last object that was added
+  # or updated.  To fix this, we add a custom command to touch archive
+  # after it's been built so that ninja won't rebuild it unnecessarily
+  # the next time it's run.
+  if(ARG_STATIC AND
+      (CMAKE_GENERATOR STREQUAL "Ninja" AND
+      (CMAKE_SYSTEM_NAME MATCHES "Darwin" AND
+        CMAKE_HOST_SYSTEM_VERSION VERSION_GREATER "15.6.0")))
+    add_custom_command(TARGET ${name}
+      POST_BUILD
+      COMMAND touch ${LLVM_LIBRARY_DIR}/${CMAKE_STATIC_LIBRARY_PREFIX}${name}${CMAKE_STATIC_LIBRARY_SUFFIX}
+      )
+  endif()
 endfunction()
 
 function(add_llvm_install_targets target)


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