Remove CMake Policy CMP0015 until it is revised

We revert commit "Create CMake Policy CMP0015 to fix set(CACHE)" because
the NEW behavior of the policy breaks a valid use case:

  # CMakeLists.txt
  option(BUILD_SHARED_LIBS "..." ON)
  add_library(mylib ...)
  set(BUILD_SHARED_LIBS OFF) # we want only mylib to be shared
  add_subdirectory(ThirdParty)

  # ThirdParty/CMakeLists.txt
  option(BUILD_SHARED_LIBS "..." ON)
  # uh, oh, with NEW behavior this dir uses shared libs!!!

We'll re-introduce the policy later with a different change in behavior
to resolve the motivating case, which was more subtle but less common.

See issue #9008.

1 files changed, 0 insertions, 31 deletions

diff --git a/Source/cmPolicies.cxx b/Source/cmPolicies.cxx
index a7292cf..0d35b65 100644
--- a/Source/cmPolicies.cxx
+++ b/Source/cmPolicies.cxx
@@ -401,37 +401,6 @@ cmPolicies::cmPolicies()
     "The OLD behavior for this policy is to silently ignore the problem.  "
     "The NEW behavior for this policy is to report an error.",
     2,8,0, cmPolicies::WARN);
-
-    this->DefinePolicy(
-    CMP0015, "CMP0015",
-    "The set() CACHE mode and option() command make the cache value visible.",
-    "In CMake 2.6 and below the CACHE mode of the set() command and the "
-    "option() command did not expose the value from the named cache entry "
-    "if it was already set both in the cache and as a local variable.  "
-    "This led to subtle differences between first and later configurations "
-    "because a conflicting local variable would be overridden only when the "
-    "cache value was first created.  "
-    "For example, the code\n"
-    "  set(x 1)\n"
-    "  set(before ${x})\n"
-    "  set(x 2 CACHE STRING \"X\")\n"
-    "  set(after ${x})\n"
-    "  message(STATUS \"${before},${after}\")\n"
-    "would print \"1,2\" on the first run and \"1,1\" on future runs."
-    "\n"
-    "CMake 2.8.0 and above prefer to expose the cache value in all cases by "
-    "removing the local variable definition, but this changes behavior in "
-    "subtle cases when the local variable has a different value than that "
-    "exposed from the cache.  "
-    "The example above will always print \"1,2\"."
-    "\n"
-    "This policy determines whether the commands should always expose the "
-    "cache value.  "
-    "The OLD behavior for this policy is to leave conflicting local "
-    "variable values untouched and hide the true cache value.  "
-    "The NEW behavior for this policy is to always expose the cache value.",
-    2,8,0, cmPolicies::WARN);
-
 }
 
 cmPolicies::~cmPolicies()