Drop compatibility with CMake < 2.4

Drop all behavior activated by setting CMAKE_BACKWARDS_COMPATIBILITY to
a value lower than 2.4, and generate an error when projects or the user
attempt to do so.  In the error suggest using a CMake 2.8.x release.

Teach cmake_minimum_required to warn about projects that do not require
at least CMake 2.4.  They are not supported by CMake >= 3.0.

Replace the documentation of CMAKE_BACKWARDS_COMPATIBILITY with a
reference to policy CMP0001.

1 files changed, 3 insertions, 12 deletions

diff --git a/Source/cmLocalGenerator.cxx b/Source/cmLocalGenerator.cxx
index 3dde19f..edf80e6 100644
--- a/Source/cmLocalGenerator.cxx
+++ b/Source/cmLocalGenerator.cxx
@@ -1412,13 +1412,6 @@ void cmLocalGenerator::GetIncludeDirectories(std::vector<std::string>& dirs,
     includeBinaryDir = true;
     }
 
-  // CMake versions below 2.0 would add the source tree to the -I path
-  // automatically.  Preserve compatibility.
-  if(this->NeedBackwardsCompatibility(1,9))
-    {
-    includeSourceDir = true;
-    }
-
   // Hack for VTK 4.0 - 4.4 which depend on the old behavior but do
   // not set the backwards compatibility level automatically.
   const char* vtkSourceDir =
@@ -3071,7 +3064,7 @@ cmLocalGenerator
     // Decide whether this language wants to replace the source
     // extension with the object extension.  For CMake 2.4
     // compatibility do this by default.
-    bool replaceExt = this->NeedBackwardsCompatibility(2, 4);
+    bool replaceExt = this->NeedBackwardsCompatibility_2_4();
     if(!replaceExt)
       {
       if(const char* lang = source.GetLanguage())
@@ -3318,9 +3311,7 @@ unsigned int cmLocalGenerator::GetBackwardsCompatibility()
 }
 
 //----------------------------------------------------------------------------
-bool cmLocalGenerator::NeedBackwardsCompatibility(unsigned int major,
-                                                  unsigned int minor,
-                                                  unsigned int patch)
+bool cmLocalGenerator::NeedBackwardsCompatibility_2_4()
 {
   // Check the policy to decide whether to pay attention to this
   // variable.
@@ -3348,7 +3339,7 @@ bool cmLocalGenerator::NeedBackwardsCompatibility(unsigned int major,
   // equal to or lower than the given version.
   unsigned int actual_compat = this->GetBackwardsCompatibility();
   return (actual_compat &&
-          actual_compat <= CMake_VERSION_ENCODE(major, minor, patch));
+          actual_compat <= CMake_VERSION_ENCODE(2, 4, 255));
 }
 
 //----------------------------------------------------------------------------