Xcode: Switch to internal CMAKE_MAKE_PROGRAM lookup by generator (#15324)

The "cmakexbuild" wrapper is not needed for Xcode 4 and above, and the
path to it may change when CMake moves.  Avoid storing a specific path
to a build program in CMakeCache.txt and instead compute the value for
CMAKE_MAKE_PROGRAM on demand.  However, if a user does set the value
explicitly then honor it.

This does for Xcode what commit v3.0.0-rc1~260^2~4 (VS: Switch to
internal CMAKE_MAKE_PROGRAM lookup by generators, 2013-11-15) did for
Visual Studio generators.

Help/release/dev/xcode-revise-make-program.rst

@@ -0,0 +1,6 @@
+xcode-revise-make-program
+-------------------------
+
+* The :generator:`Xcode` generator no longer requires a value for
+  the :variable:`CMAKE_MAKE_PROGRAM` variable to be located up front.
+  It now locates ``xcodebuild`` when needed at build time.

Help/variable/CMAKE_MAKE_PROGRAM.rst

@@ -23,8 +23,15 @@ to configure the project:
   otherwise undocumented ``cmakexbuild`` wrapper implementing some
   workarounds).
 
-  This generator stores ``CMAKE_MAKE_PROGRAM`` in the CMake cache
-  so that it may be edited by the user.
+  This generator prefers to lookup the build tool at build time
+  rather than to store ``CMAKE_MAKE_PROGRAM`` in the CMake cache
+  ahead of time.  This is because ``xcodebuild`` is easy to find,
+  the ``cmakexbuild`` wrapper is needed only for older Xcode versions,
+  and the path to ``cmakexbuild`` may be outdated if CMake itself moves.
+
+  For compatibility with versions of CMake prior to 3.2, if
+  a user or project explicitly adds ``CMAKE_MAKE_PROGRAM`` to
+  the CMake cache then CMake will use the specified value.
 
 * The Visual Studio generators set this to the full path to
   ``MSBuild.exe`` (VS >= 10), ``devenv.com`` (VS 7,8,9),

Modules/CMakeFindXCode.cmake

@@ -12,9 +12,5 @@
 # (To distribute this file outside of CMake, substitute the full
 #  License text for the above reference.)
 
-find_program(CMAKE_MAKE_PROGRAM
-  NAMES xcodebuild
-  PATHS
-  /usr/bin
-  )
-mark_as_advanced(CMAKE_MAKE_PROGRAM)
+# Empty placeholder for input dependencies in existing
+# build trees produced by older versions of CMake.

Source/cmGlobalGenerator.cxx

@@ -315,25 +315,6 @@ void cmGlobalGenerator::FindMakeProgram(cmMakefile* mf)
                            "make program",
                            cmCacheManager::FILEPATH);
     }
-
-  if(makeProgram.find("xcodebuild") != makeProgram.npos)
-    {
-    // due to the text file busy /bin/sh problem with xcodebuild
-    // use the cmakexbuild wrapper instead.  This program
-    // will run xcodebuild and if it sees the error text file busy
-    // it will stop forwarding output, and let the build finish.
-    // Then it will retry the build.  It will continue this
-    // until no text file busy errors occur.
-    std::string cmakexbuild =
-      this->CMakeInstance->GetCacheManager()->GetCacheValue("CMAKE_COMMAND");
-    cmakexbuild = cmakexbuild.substr(0, cmakexbuild.length()-5);
-    cmakexbuild += "cmakexbuild";
-
-    mf->AddCacheDefinition("CMAKE_MAKE_PROGRAM",
-                           cmakexbuild.c_str(),
-                           "make program",
-                           cmCacheManager::FILEPATH);
-    }
 }
 
 // enable the given language

Source/cmGlobalXCodeGenerator.cxx

@@ -136,7 +136,6 @@ cmGlobalXCodeGenerator::cmGlobalXCodeGenerator(std::string const& version)
   sscanf(this->VersionString.c_str(), "%u.%u", &v[0], &v[1]);
   this->XcodeVersion = 10*v[0] + v[1];
 
-  this->FindMakeProgramFile = "CMakeFindXCode.cmake";
   this->RootObject = 0;
   this->MainGroupChildren = 0;
   this->SourcesGroupChildren = 0;
@@ -202,6 +201,19 @@ cmGlobalGenerator* cmGlobalXCodeGenerator::Factory
 #endif
 }
 
+//----------------------------------------------------------------------------
+void cmGlobalXCodeGenerator::FindMakeProgram(cmMakefile* mf)
+{
+  // The Xcode generator knows how to lookup its build tool
+  // directly instead of needing a helper module to do it, so we
+  // do not actually need to put CMAKE_MAKE_PROGRAM into the cache.
+  if(cmSystemTools::IsOff(mf->GetDefinition("CMAKE_MAKE_PROGRAM")))
+    {
+    mf->AddDefinition("CMAKE_MAKE_PROGRAM",
+                      this->GetXcodeBuildCommand().c_str());
+    }
+}
+
 //----------------------------------------------------------------------------
 std::string const& cmGlobalXCodeGenerator::GetXcodeBuildCommand()
 {

Source/cmGlobalXCodeGenerator.h

@@ -70,6 +70,8 @@ public:
                                         const std::string& suffix,
                                         std::string& dir);
 
+  virtual void FindMakeProgram(cmMakefile*);
+
   ///! What is the configurations directory variable called?
   virtual const char* GetCMakeCFGIntDir() const;
   ///! expand CFGIntDir

Tests/CMakeLists.txt

@@ -51,7 +51,7 @@ if(BUILD_TESTING)
     set(CMake_TEST_DEVENV "${CMAKE_MAKE_PROGRAM}")
   endif()
 
-  if(CMAKE_GENERATOR MATCHES "Visual Studio")
+  if(CMAKE_GENERATOR MATCHES "Visual Studio|Xcode")
     set(CMake_TEST_EXPLICIT_MAKE_PROGRAM "")
   else()
     set(CMake_TEST_EXPLICIT_MAKE_PROGRAM "${CMAKE_MAKE_PROGRAM}")