[PATCH] D27119: Use Darwin libtool's -no_warning_for_no_symbols if available to silence the "has no symbols" link warning

[Kuba (Brecka) Mracek via llvm-commits]

kubabrecka created this revision.
kubabrecka added reviewers: beanz, bogner, pete, zaks.anna.
kubabrecka added a subscriber: llvm-commits.
kubabrecka set the repository for this revision to rL LLVM.
Herald added a subscriber: mgorny.

Building compiler-rt on Darwin produces dozens of meaningless warnings about object files having no symbols during static archive creation.  This is very intentional as compiler-rt uses #ifdefs to conditionally compile platform-specific code, and we even have a .cpp source file that only contains static asserts to make sure the environment is configured right.  On Linux, this situation is fine and no warning is produces.  This patch adds a libtool version detection and if it's new enough, we'll use the `-no_warning_for_no_symbols` flag that suppresses this warning.  Build logs should be much cleaner now!


Repository:
  rL LLVM

https://reviews.llvm.org/D27119

Files:
  CMakeLists.txt


Index: CMakeLists.txt
===================================================================
--- CMakeLists.txt
+++ CMakeLists.txt
@@ -73,9 +73,23 @@
   if(CMAKE_LIBTOOL)
     set(CMAKE_LIBTOOL ${CMAKE_LIBTOOL} CACHE PATH "libtool executable")
     message(STATUS "Found libtool - ${CMAKE_LIBTOOL}")
+
+    set(LIBTOOL_NO_WARNING_FLAG "")
+    execute_process(COMMAND ${CMAKE_LIBTOOL} -V
+      OUTPUT_VARIABLE LIBTOOL_V_OUTPUT
+      OUTPUT_STRIP_TRAILING_WHITESPACE)
+    if("${LIBTOOL_V_OUTPUT}" MATCHES ".*cctools-([0-9.]+).*")
+      string(REGEX REPLACE ".*cctools-([0-9.]+).*" "\\1" LIBTOOL_VERSION
+        ${LIBTOOL_V_OUTPUT})
+      if(NOT LIBTOOL_VERSION VERSION_LESS "862")
+        set(LIBTOOL_NO_WARNING_FLAG "-no_warning_for_no_symbols")
+      endif()
+    endif()
+    
     foreach(lang ${languages})
       set(CMAKE_${lang}_CREATE_STATIC_LIBRARY
-        "${CMAKE_LIBTOOL} -static -o <TARGET> <LINK_FLAGS> <OBJECTS> ")
+        "${CMAKE_LIBTOOL} -static ${LIBTOOL_NO_WARNING_FLAG} -o <TARGET> "
+        "<LINK_FLAGS> <OBJECTS> ")
     endforeach()
   endif()
 


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