[builtins] Prevent racing between setting supported architectures in builtin-config-ix and config-ix

[george.karpenkov]

Summary

Both builtin-config-ix and config-ix set variables DARWIN_${platform}_ARCHS to indicate supporting architectures.
Those variables are cached, so the writes race, and the first write wins.
Currently, everything was working as expected because in builtins-only mode only builtins would be compiled, and otherwise, config-ix was processed first, winning the race.

Upon closer inspection, builtin-config-ix does not even use the created variables DARWIN_${platform}_ARCHS, and simply populates it's own variables.
This patch fixes the race by postfixing the variables used in builtin-* with BUILTIN.

[kubamracek]

AFAICT, this looks good.

[delcypher]

cmake/builtin-config-ix.cmake

130

We had an offline conversation about this but I'm not sure if we resolved the issue.
This looks wrong DARWIN_${platform}sim_ARCHS_builtin} is not an architecture name and it doesn't look like this variable name gets expanded in darwin_test_archs() AFAICT.

149

Same problem here.

cmake/builtin-config-ix.cmake

set(DARWIN_tvos_BUILTIN_MIN_VER_FLAG
       ${DARWIN_tvos_MIN_VER_FLAG}=${DARWIN_tvos_BUILTIN_MIN_VER})
   endif()
 
   set(BUILTIN_SUPPORTED_OS osx)
 
   # We're setting the flag manually for each target OS
   set(CMAKE_OSX_DEPLOYMENT_TARGET "")
 
-  if(NOT DARWIN_osx_ARCHS)
-    set(DARWIN_osx_ARCHS i386 x86_64 x86_64h)
+  if(NOT DARWIN_osx_ARCHS_builtin)
+    set(DARWIN_osx_ARCHS_builtin i386 x86_64 x86_64h)
   endif()
 
-  set(DARWIN_sim_ARCHS i386 x86_64)
-  set(DARWIN_device_ARCHS armv7 armv7s armv7k arm64)
+  set(DARWIN_sim_ARCHS_builtin i386 x86_64)
+  set(DARWIN_device_ARCHS_builtin armv7 armv7s armv7k arm64)
 
-  message(STATUS "OSX supported arches: ${DARWIN_osx_ARCHS}")
-  foreach(arch ${DARWIN_osx_ARCHS})
+  message(STATUS "OSX supported arches: ${DARWIN_osx_ARCHS_builtin}")
+  foreach(arch ${DARWIN_osx_ARCHS_builtin})
     list(APPEND COMPILER_RT_SUPPORTED_ARCH ${arch})
     set(CAN_TARGET_${arch} 1)
   endforeach()
 
   # Need to build a 10.4 compatible libclang_rt
   set(DARWIN_10.4_SYSROOT ${DARWIN_osx_SYSROOT})
   set(DARWIN_10.4_BUILTIN_MIN_VER 10.4)
   set(DARWIN_10.4_BUILTIN_MIN_VER_FLAG
       -mmacosx-version-min=${DARWIN_10.4_BUILTIN_MIN_VER})
   set(DARWIN_10.4_SKIP_CC_KEXT On)
-  darwin_test_archs(10.4 DARWIN_10.4_ARCHS i386 x86_64)
-  message(STATUS "OSX 10.4 supported builtin arches: ${DARWIN_10.4_ARCHS}")
-  if(DARWIN_10.4_ARCHS)
+  darwin_test_archs(10.4 DARWIN_10.4_ARCHS_builtin i386 x86_64)
+  message(STATUS "OSX 10.4 supported builtin arches: ${DARWIN_10.4_ARCHS_builtin}")
+  if(DARWIN_10.4_ARCHS_builtin)
     # don't include the Haswell slice in the 10.4 compatibility library
-    list(REMOVE_ITEM DARWIN_10.4_ARCHS x86_64h)
+    list(REMOVE_ITEM DARWIN_10.4_ARCHS_builtin x86_64h)
     list(APPEND BUILTIN_SUPPORTED_OS 10.4)
   endif()
 
   foreach(platform ${DARWIN_EMBEDDED_PLATFORMS})
     if(DARWIN_${platform}sim_SYSROOT)
       set(DARWIN_${platform}sim_BUILTIN_MIN_VER
         ${DARWIN_${platform}_BUILTIN_MIN_VER})
       set(DARWIN_${platform}sim_BUILTIN_MIN_VER_FLAG
         ${DARWIN_${platform}_BUILTIN_MIN_VER_FLAG})
 
       set(DARWIN_${platform}sim_SKIP_CC_KEXT On)
 
-      set(test_arches ${DARWIN_sim_ARCHS})
-      if(DARWIN_${platform}sim_ARCHS)
-        set(test_arches DARWIN_${platform}sim_ARCHS)
+      set(test_arches ${DARWIN_sim_ARCHS_builtin})
+      if(DARWIN_${platform}sim_ARCHS_builtin)
+        set(test_arches DARWIN_${platform}sim_ARCHS_builtin)
       endif()
 
       darwin_test_archs(${platform}sim
-        DARWIN_${platform}sim_ARCHS
+        DARWIN_${platform}sim_ARCHS_builtin
         ${test_arches})
-      message(STATUS "${platform} Simulator supported builtin arches: ${DARWIN_${platform}sim_ARCHS}")
-      if(DARWIN_${platform}sim_ARCHS)
+      message(STATUS "${platform} Simulator supported builtin arches: ${DARWIN_${platform}sim_ARCHS_builtin}")
+      if(DARWIN_${platform}sim_ARCHS_builtin)
         list(APPEND BUILTIN_SUPPORTED_OS ${platform}sim)
       endif()
-      foreach(arch ${DARWIN_${platform}sim_ARCHS})
+      foreach(arch ${DARWIN_${platform}sim_ARCHS_builtin})
         list(APPEND COMPILER_RT_SUPPORTED_ARCH ${arch})
         set(CAN_TARGET_${arch} 1)
       endforeach()
     endif()
 
     if(DARWIN_${platform}_SYSROOT)
-      set(test_arches ${DARWIN_device_ARCHS})
-      if(DARWIN_${platform}_ARCHS)
-        set(test_arches DARWIN_${platform}_ARCHS)
+      set(test_arches ${DARWIN_device_ARCHS_builtin})
+      if(DARWIN_${platform}_ARCHS_builtin)
+        set(test_arches DARWIN_${platform}_ARCHS_builtin)
       endif()
 
       darwin_test_archs(${platform}
-        DARWIN_${platform}_ARCHS
+        DARWIN_${platform}_ARCHS_builtin
         ${test_arches})
-      message(STATUS "${platform} supported builtin arches: ${DARWIN_${platform}_ARCHS}")
-      if(DARWIN_${platform}_ARCHS)
+      message(STATUS "${platform} supported builtin arches: ${DARWIN_${platform}_ARCHS_builtin}")
+      if(DARWIN_${platform}_ARCHS_builtin)
         list(APPEND BUILTIN_SUPPORTED_OS ${platform})
       endif()
-      foreach(arch ${DARWIN_${platform}_ARCHS})
+      foreach(arch ${DARWIN_${platform}_ARCHS_builtin})
         list(APPEND COMPILER_RT_SUPPORTED_ARCH ${arch})
         set(CAN_TARGET_${arch} 1)
       endforeach()
     endif()
   endforeach()
 
   list_intersect(BUILTIN_SUPPORTED_ARCH ALL_BUILTIN_SUPPORTED_ARCH COMPILER_RT_SUPPORTED_ARCH)