Fix C++11 detection for VS2010.

- Use cmake_dependent_option() for all threading models and encode their
  respective mutual exclusivity in the dependent-option s/t the job of
  ensuring mutual exclusivity is performed by CMake.
- Use of cmake_dependent_option() has the downside that options are
  removed from the GUI if their requirements for availability are not
  met.  So if CXX11 is OFF, then neither TBB nor CXX11_THREADS will
  even appear as options (they will be undefined, assumed OFF).
- Perform checks for availability of C++11 if CXX11 is enabled prior to
  testing other options to handle dependence of TBB & CXX11_THREADS on
  CXX11 actually being present.
- Add check for availability of C++11-specific math functions used in
  jet.h before reporting C++11 as found.
- Add check for <atomic> before allowing TBB or CXX11_THREADS, as both
  options require it and it may not always be available even if the
  other required C++11 components are.

Change-Id: Ife8cd182aeb1978539ce2c9966910ae59ebd9177

cmake/FindCXX11MathFunctions.cmake

@@ -0,0 +1,58 @@
+# Ceres Solver - A fast non-linear least squares minimizer
+# Copyright 2015 Google Inc. All rights reserved.
+# http://ceres-solver.org/
+#
+# Redistribution and use in source and binary forms, with or without
+# modification, are permitted provided that the following conditions are met:
+#
+# * Redistributions of source code must retain the above copyright notice,
+#   this list of conditions and the following disclaimer.
+# * Redistributions in binary form must reproduce the above copyright notice,
+#   this list of conditions and the following disclaimer in the documentation
+#   and/or other materials provided with the distribution.
+# * Neither the name of Google Inc. nor the names of its contributors may be
+#   used to endorse or promote products derived from this software without
+#   specific prior written permission.
+#
+# THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS "AS IS"
+# AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
+# IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
+# ARE DISCLAIMED. IN NO EVENT SHALL THE COPYRIGHT OWNER OR CONTRIBUTORS BE
+# LIABLE FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR
+# CONSEQUENTIAL DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF
+# SUBSTITUTE GOODS OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS
+# INTERRUPTION) HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN
+# CONTRACT, STRICT LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE)
+# ARISING IN ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
+# POSSIBILITY OF SUCH DAMAGE.
+#
+# Author: alexs.mac@gmail.com (Alex Stewart)
+#
+
+# FindCXX11MathFunctions.cmake - Find C++11 math functions.
+#
+# This module defines the following variables:
+#
+# CXX11_MATH_FUNCTIONS_FOUND: TRUE if C++11 math functions are found.
+
+macro(find_cxx11_math_functions)
+  # To support CXX11 option, clear the results of all check_xxx() functions
+  # s/t we always perform the checks each time, otherwise CMake fails to
+  # detect that the tests should be performed again after CXX11 is toggled.
+  unset(CXX11_MATH_FUNCTIONS_FOUND CACHE)
+
+  # Verify that all C++11-specific math functions used by jet.h exist.
+  check_cxx_source_compiles("#include <cmath>
+                             #include <cstddef>
+                             static constexpr size_t kMaxAlignBytes = alignof(std::max_align_t);
+                             int main() {
+                                std::cbrt(1.0);
+                                std::exp2(1.0);
+                                std::log2(1.0);
+                                std::hypot(1.0, 1.0);
+                                std::fmax(1.0, 1.0);
+                                std::fmin(1.0, 1.0);
+                                return 0;
+                             }"
+                             CXX11_MATH_FUNCTIONS_FOUND)
+endmacro()

cmake/UpdateCacheVariable.cmake

@@ -37,6 +37,11 @@
 # for the cache variable to update, then reinitialising it with the new
 # value, but with the original help string.
 function(UPDATE_CACHE_VARIABLE VAR_NAME VALUE)
+  get_property(IS_DEFINED_IN_CACHE CACHE ${VAR_NAME} PROPERTY VALUE SET)
+  if (NOT IS_DEFINED_IN_CACHE)
+    message(FATAL_ERROR "Specified variable to update in cache: "
+      "${VAR_NAME} has not been set in the cache.")
+  endif()
   get_property(HELP_STRING CACHE ${VAR_NAME} PROPERTY HELPSTRING)
   get_property(VAR_TYPE CACHE ${VAR_NAME} PROPERTY TYPE)
   set(${VAR_NAME} ${VALUE} CACHE ${VAR_TYPE} "${HELP_STRING}" FORCE)