From: Daniel Sanders <daniel_l_sanders@apple.com>
Date: Tue, 19 Feb 2019 19:45:03 +0000 (+0000)
Subject: Fix builds for older macOS deployment targets after r354365
X-Git-Url: https://granicus.if.org/sourcecode?a=commitdiff_plain;h=660bc13d97e2929e16e40ac2975841185130e594;p=llvm

Fix builds for older macOS deployment targets after r354365

Surprisingly, check_symbol_exists is not sufficient. The macOS linker checks the
called functions against a compatibility list for the given deployment target
and check_symbol_exists doesn't trigger this check as it never calls the
function.

This fixes the GreenDragon bots where the deployment target is 10.9


git-svn-id: https://llvm.org/svn/llvm-project/llvm/trunk@354374 91177308-0d34-0410-b5e6-96231b3b80d8
---

diff --git a/cmake/modules/HandleLLVMOptions.cmake b/cmake/modules/HandleLLVMOptions.cmake
index f60b457679e..694fe946b9b 100644
--- a/cmake/modules/HandleLLVMOptions.cmake
+++ b/cmake/modules/HandleLLVMOptions.cmake
@@ -917,25 +917,31 @@ get_compile_definitions()
 
 option(LLVM_FORCE_ENABLE_STATS "Enable statistics collection for builds that wouldn't normally enable it" OFF)
 
-check_symbol_exists(os_signpost_interval_begin "os/signpost.h" _signposts_available)
-if(_signposts_available)
-  set(LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS "WITH_ASSERTS" CACHE STRING
-      "Enable support for Xcode signposts. Can be WITH_ASSERTS, FORCE_ON, FORCE_OFF")
-  string(TOUPPER "${LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS}"
-                 uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS)
-  if( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "WITH_ASSERTS" )
-    if( LLVM_ENABLE_ASSERTIONS )
+check_symbol_exists(os_signpost_interval_begin "os/signpost.h" macos_signposts_available)
+if(macos_signposts_available)
+  check_cxx_source_compiles(
+    "#include <os/signpost.h>
+    int main() { os_signpost_interval_begin(nullptr, 0, \"\", \"\"); return 0; }"
+    macos_signposts_usable)
+  if(macos_signposts_usable)
+    set(LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS "WITH_ASSERTS" CACHE STRING
+        "Enable support for Xcode signposts. Can be WITH_ASSERTS, FORCE_ON, FORCE_OFF")
+    string(TOUPPER "${LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS}"
+                   uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS)
+    if( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "WITH_ASSERTS" )
+      if( LLVM_ENABLE_ASSERTIONS )
+        set( LLVM_SUPPORT_XCODE_SIGNPOSTS 1 )
+      endif()
+    elseif( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "FORCE_ON" )
       set( LLVM_SUPPORT_XCODE_SIGNPOSTS 1 )
+    elseif( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "FORCE_OFF" )
+      # We don't need to do anything special to turn off signposts.
+    elseif( NOT DEFINED LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS )
+      # Treat LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS like "FORCE_OFF" when it has not been
+      # defined.
+    else()
+      message(FATAL_ERROR "Unknown value for LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS:"
+                          " \"${LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS}\"!")
     endif()
-  elseif( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "FORCE_ON" )
-    set( LLVM_SUPPORT_XCODE_SIGNPOSTS 1 )
-  elseif( uppercase_LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS STREQUAL "FORCE_OFF" )
-    # We don't need to do anything special to turn off signposts.
-  elseif( NOT DEFINED LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS )
-    # Treat LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS like "FORCE_OFF" when it has not been
-    # defined.
-  else()
-    message(FATAL_ERROR "Unknown value for LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS:"
-                        " \"${LLVM_ENABLE_SUPPORT_XCODE_SIGNPOSTS}\"!")
   endif()
 endif()