cmTarget: Include TARGET_OBJECTS genex in target SOURCES property.

Add policy CMP0051 to control this behavior.

1 files changed, 24 insertions, 0 deletions

diff --git a/Help/policy/CMP0051.rst b/Help/policy/CMP0051.rst
new file mode 100644
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+++ b/Help/policy/CMP0051.rst
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+CMP0051
+-------
+
+List TARGET_OBJECTS in SOURCES target property.
+
+CMake 3.0 and lower did not include the ``TARGET_OBJECTS``
+:manual:`generator expression <cmake-generator-expressions(7)>` when
+returning the :prop_tgt:`SOURCES` target property.
+
+Configure-time CMake code is not able to handle generator expressions.  If
+using the :prop_tgt:`SOURCES` target property at configure time, it may be
+necessary to first remove generator expressions using the
+:command:`string(STRIP_GENEX)` command.  Generate-time CMake code such as
+:command:`file(GENERATE)` can handle the content without stripping.
+
+The ``OLD`` behavior for this policy is to omit ``TARGET_OBJECTS``
+expressions from the :prop_tgt:`SOURCES` target property.  The ``NEW``
+behavior for this policy is to include ``TARGET_OBJECTS`` expressions
+in the output.
+
+This policy was introduced in CMake version 3.1.
+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.