export: Add policy CMP0024 to disallow include() of export files

Currently, export() is executed at configure-time.

One problem with this is that certain exported properties like
the link interface may not be complete at the point the export() is
encountered leading to an incorrect or incomplete exported
representation. Additionally, the generated IMPORTED_LOCATION
property may even be incorrect if commands following the export()
have an effect on it.

Another problem is that it requires the C++ implementation of cmake
to be capable of computing the exported information at configure time.
This is a limitation on the cleanup and maintenance of the code. At
some point in the future, this limitation will be dropped and more
implementation will be moved from cmTarget to cmGeneratorTarget.

1 files changed, 15 insertions, 0 deletions

diff --git a/Tests/RunCMake/include/CMP0024-NEW-stderr.txt b/Tests/RunCMake/include/CMP0024-NEW-stderr.txt
new file mode 100644
index 0000000..182c67a
--- /dev/null
+++ b/Tests/RunCMake/include/CMP0024-NEW-stderr.txt
@@ -0,0 +1,15 @@
+CMake Error at CMP0024-NEW.cmake:9 \(include\):
+  Policy CMP0024 is not set: Disallow include export result.  Run "cmake
+  --help-policy CMP0024" for policy details.  Use the cmake_policy command to
+  set the policy and suppress this warning.
+
+  The file
+
+    .*/Tests/RunCMake/include/CMP0024-NEW-build/theTargets.cmake
+
+  was generated by the export\(\) command.  It may not be used as the argument
+  to the include\(\) command.  Use ALIAS targets instead to refer to targets by
+  alternative names.
+
+Call Stack \(most recent call first\):
+  CMakeLists.txt:3 \(include\)