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, 0 insertions, 18 deletions

diff --git a/Source/cmFindBase.cxx b/Source/cmFindBase.cxx
index c1e7b1e..ae15ee7 100644
--- a/Source/cmFindBase.cxx
+++ b/Source/cmFindBase.cxx
@@ -28,11 +28,6 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
     return false;
     }
 
-  // CMake versions below 2.3 did not search all these extra
-  // locations.  Preserve compatibility unless a modern argument is
-  // passed.
-  bool compatibility = this->Makefile->NeedBackwardsCompatibility(2,3);
-
   // copy argsIn into args so it can be modified,
   // in the process extract the DOC "documentation"
   size_t size = argsIn.size();
@@ -112,7 +107,6 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
     else if (args[j] == "PATH_SUFFIXES")
       {
       doing = DoingPathSuffixes;
-      compatibility = false;
       newStyle = true;
       }
     else if (args[j] == "NAMES_PER_DIR")
@@ -136,7 +130,6 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
     else if (this->CheckCommonArgument(args[j]))
       {
       doing = DoingNone;
-      compatibility = false;
       // Some common arguments were accidentally supported by CMake
       // 2.4 and 2.6.0 in the short-hand form of the command, so we
       // must support it even though it is not documented.
@@ -159,17 +152,6 @@ bool cmFindBase::ParseArguments(std::vector<std::string> const& argsIn)
       }
     }
 
-  // Now that arguments have been parsed check the compatibility
-  // setting.  If we need to be compatible with CMake 2.2 and earlier
-  // do not add the CMake system paths.  It is safe to add the CMake
-  // environment paths and system environment paths because that
-  // existed in 2.2.  It is safe to add the CMake user variable paths
-  // because the user or project has explicitly set them.
-  if(compatibility)
-    {
-    this->NoCMakeSystemPath = true;
-    }
-
   if(this->VariableDocumentation.size() == 0)
     {
     this->VariableDocumentation = "Where can ";