export(): raise an error on multiple calls with same FILE

Fixes: 20472

1 files changed, 22 insertions, 0 deletions

diff --git a/Help/policy/CMP0103.rst b/Help/policy/CMP0103.rst
new file mode 100644
index 0000000..223e0cb
--- /dev/null
+++ b/Help/policy/CMP0103.rst
@@ -0,0 +1,22 @@
+CMP0103
+-------
+
+Multiple calls to :command:`export` command with same ``FILE`` without
+``APPEND`` is no longer allowed.
+
+In CMake 3.17 and below, multiple calls to :command:`export` command with the
+same ``FILE`` without ``APPEND`` are accepted silently but only the last
+occurrence is taken into account during the generation.
+
+The ``OLD`` behavior for this policy is to ignore the multiple occurrences of
+ :command:`export` command except the last one.
+
+The ``NEW`` behavior of this policy is to raise an error on second call to
+:command:`export` command with same ``FILE`` without ``APPEND``.
+
+This policy was introduced in CMake version 3.18.  CMake version
+|release| warns when the policy is not set and uses ``OLD`` behavior.
+Use the :command:`cmake_policy` command to set it to ``OLD`` or ``NEW``
+explicitly.
+
+.. include:: DEPRECATED.txt