VS: Select highest available CUDA toolset by default

If `CMAKE_GENERATOR_TOOLSET` does not have a `cuda=...` field then
find available CUDA toolsets and choose the highest version.

Help/variable/CMAKE_VS_PLATFORM_TOOLSET_CUDA.rst

@@ -6,5 +6,7 @@ NVIDIA CUDA Toolkit version whose Visual Studio toolset to use.
 The :ref:`Visual Studio Generators` for VS 2010 and above support using
 a CUDA toolset provided by a CUDA Toolkit.  The toolset version number
 may be specified by a field in :variable:`CMAKE_GENERATOR_TOOLSET` of
-the form ``cuda=8.0``.  CMake provides the selected CUDA toolset version
-in this variable.  The value may be empty if no version was specified.
+the form ``cuda=8.0``.  If none is specified CMake will choose a default
+version.  CMake provides the selected CUDA toolset version in this variable.
+The value may be empty if no CUDA Toolkit with Visual Studio integration
+is installed.

Source/cmGlobalVisualStudio10Generator.cxx

@@ -22,8 +22,11 @@
 #include "cmake.h"
 
 #include <cmsys/FStream.hxx>
+#include <cmsys/Glob.hxx>
 #include <cmsys/RegularExpression.hxx>
 
+#include <algorithm>
+
 static const char vs10generatorName[] = "Visual Studio 10 2010";
 
 // Map generator name without year to name with year.
@@ -160,6 +163,13 @@ bool cmGlobalVisualStudio10Generator::SetGeneratorPlatform(
   return true;
 }
 
+static void cmCudaToolVersion(std::string& s)
+{
+  // "CUDA x.y.props" => "x.y"
+  s = s.substr(5);
+  s = s.substr(0, s.size() - 6);
+}
+
 bool cmGlobalVisualStudio10Generator::SetGeneratorToolset(
   std::string const& ts, cmMakefile* mf)
 {
@@ -180,6 +190,23 @@ bool cmGlobalVisualStudio10Generator::SetGeneratorToolset(
     return false;
   }
 
+  if (this->GeneratorToolsetCuda.empty()) {
+    // Find the highest available version of the CUDA tools.
+    std::vector<std::string> cudaTools;
+    std::string const bcDir = this->VCTargetsPath + "/BuildCustomizations";
+    cmsys::Glob gl;
+    gl.SetRelative(bcDir.c_str());
+    if (gl.FindFiles(bcDir + "/CUDA *.props")) {
+      cudaTools = gl.GetFiles();
+    }
+    if (!cudaTools.empty()) {
+      std::for_each(cudaTools.begin(), cudaTools.end(), cmCudaToolVersion);
+      std::sort(cudaTools.begin(), cudaTools.end(),
+                cmSystemTools::VersionCompareGreater);
+      this->GeneratorToolsetCuda = cudaTools.at(0);
+    }
+  }
+
   if (const char* toolset = this->GetPlatformToolset()) {
     mf->AddDefinition("CMAKE_VS_PLATFORM_TOOLSET", toolset);
   }