Add the ALIAS target concept for libraries and executables.

* The ALIAS name must match a validity regex.
* Executables and libraries may be aliased.
* An ALIAS acts immutable. It can not be used as the lhs
  of target_link_libraries or other commands.
* An ALIAS can be used with add_custom_command, add_custom_target,
  and add_test in the same way regular targets can.
* The target of an ALIAS can be retrieved with the ALIASED_TARGET
  target property.
* An ALIAS does not appear in the generated buildsystem. It
  is kept separate from cmMakefile::Targets for that reason.
* A target may have multiple aliases.
* An ALIAS target may not itself have an alias.
* An IMPORTED target may not have an alias.
* An ALIAS may not be exported or imported.

1 files changed, 9 insertions, 0 deletions

diff --git a/Source/cmExportCommand.cxx b/Source/cmExportCommand.cxx
index 9c3f314..f059ceb 100644
--- a/Source/cmExportCommand.cxx
+++ b/Source/cmExportCommand.cxx
@@ -114,6 +114,15 @@ bool cmExportCommand
       currentTarget != this->Targets.GetVector().end();
       ++currentTarget)
     {
+    if (this->Makefile->IsAlias(currentTarget->c_str()))
+      {
+      cmOStringStream e;
+      e << "given ALIAS target \"" << *currentTarget
+        << "\" which may not be exported.";
+      this->SetError(e.str().c_str());
+      return false;
+      }
+
     if(cmTarget* target =
        this->Makefile->GetLocalGenerator()->
        GetGlobalGenerator()->FindTarget(0, currentTarget->c_str()))