CPack add necessary check to detect/warns/error on ABSOLUTE DESTINATION

The [usually] wrong usage of absolute DESTINATION in INSTALL rules
keeps popping-up on the ML. We shall have some way to:
  1) easily detect it.
  2) forbids this for some CPack generator like NSIS
In fact it should certainly be forbidden for *any* generators
when used on Windows but we may implements that on top of the current
patch.
The patch ask the task to the generated cmake_install.cmake scripts.
Those scripts are a little bit more complicated with that but
iff there are absolute DESTINATION. This cost nothing if relative
DESTINATION are used.
Two new vars are introduced (and documented to handle that):
CPACK_WARN_ON_ABSOLUTE_INSTALL_DESTINATION
and
CPACK_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION

1 files changed, 25 insertions, 0 deletions

diff --git a/Source/CPack/cmCPackGenerator.cxx b/Source/CPack/cmCPackGenerator.cxx
index bf65271..ca790c0 100644
--- a/Source/CPack/cmCPackGenerator.cxx
+++ b/Source/CPack/cmCPackGenerator.cxx
@@ -849,8 +849,27 @@ int cmCPackGenerator::InstallProjectViaInstallCMakeProjects(
           filesBefore = glB.GetFiles();
           std::sort(filesBefore.begin(),filesBefore.end());
           }
+
+        // If CPack was asked to warn on ABSOLUTE INSTALL DESTINATION
+        // then forward request to cmake_install.cmake script
+        if (this->GetOption("CPACK_WARN_ON_ABSOLUTE_INSTALL_DESTINATION"))
+          {
+            mf->AddDefinition("CPACK_WARN_ON_ABSOLUTE_INSTALL_DESTINATION",
+                              "1");
+          }
+        // If current CPack generator does support
+        // ABSOLUTE INSTALL DESTINATION or CPack has been asked for
+        // then ask cmake_install.cmake script to error out
+        // as soon as it occurs (before installing file)
+        if (!SupportsAbsoluteDestination() ||
+            this->GetOption("CPACK_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION"))
+          {
+            mf->AddDefinition("CPACK_ERROR_ON_ABSOLUTE_INSTALL_DESTINATION",
+                              "1");
+          }
         // do installation
         int res = mf->ReadListFile(0, installFile.c_str());
+
         // Now rebuild the list of files after installation
         // of the current component (if we are in component install)
         if (componentInstall)
@@ -1461,6 +1480,12 @@ cmCPackGenerator::SupportsSetDestdir() const
 }
 
 //----------------------------------------------------------------------
+bool cmCPackGenerator::SupportsAbsoluteDestination() const
+{
+  return true;
+}
+
+//----------------------------------------------------------------------
 bool cmCPackGenerator::SupportsComponentInstallation() const
 {
   return false;