From 07612646fe28d86330cbd4db9cfd27be1d8fb90f Mon Sep 17 00:00:00 2001
From: Brad King <brad.king@kitware.com>
Date: Thu, 12 Dec 2019 11:22:00 -0500
Subject: VS: Fix support for v142 toolset minor versions in VS 16.5+

The fix in commit 5117389931 (VS: Fix support for v142 toolset minor
versions, 2019-10-01, v3.15.5~6^2) worked around a bug in VS's placement
of toolset files.   VS 16.5 will fix that bug and restore the original
pattern for locations of toolset files.  Update our logic to look for
both possibilities.

Issue: #19779
---
 Modules/CMakeDetermineCompilerId.cmake            |  7 ++++---
 Source/cmGlobalVisualStudioVersionedGenerator.cxx | 20 +++++++++++---------
 2 files changed, 15 insertions(+), 12 deletions(-)

diff --git a/Modules/CMakeDetermineCompilerId.cmake b/Modules/CMakeDetermineCompilerId.cmake
index d9002fb..edbc23b 100644
--- a/Modules/CMakeDetermineCompilerId.cmake
+++ b/Modules/CMakeDetermineCompilerId.cmake
@@ -284,10 +284,11 @@ Id flags: ${testflags} ${CMAKE_${lang}_COMPILER_ID_FLAGS_ALWAYS}
           set(id_cl icl.exe)
         endif()
         if(CMAKE_VS_PLATFORM_TOOLSET_VERSION)
+          set(id_sep "\\")
           if(CMAKE_VS_PLATFORM_TOOLSET_VERSION VERSION_GREATER_EQUAL "14.20")
-            set(id_sep ".")
-          else()
-            set(id_sep "\\")
+            if(EXISTS "${CMAKE_GENERATOR_INSTANCE}/VC/Auxiliary/Build.${CMAKE_VS_PLATFORM_TOOLSET_VERSION}/Microsoft.VCToolsVersion.${CMAKE_VS_PLATFORM_TOOLSET_VERSION}.props")
+              set(id_sep ".")
+            endif()
           endif()
           set(id_toolset_version_props "<Import Project=\"${CMAKE_GENERATOR_INSTANCE}\\VC\\Auxiliary\\Build${id_sep}${CMAKE_VS_PLATFORM_TOOLSET_VERSION}\\Microsoft.VCToolsVersion.${CMAKE_VS_PLATFORM_TOOLSET_VERSION}.props\" />")
           unset(id_sep)
diff --git a/Source/cmGlobalVisualStudioVersionedGenerator.cxx b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
index 1eca1f6..66a57eb 100644
--- a/Source/cmGlobalVisualStudioVersionedGenerator.cxx
+++ b/Source/cmGlobalVisualStudioVersionedGenerator.cxx
@@ -388,15 +388,17 @@ std::string cmGlobalVisualStudioVersionedGenerator::GetAuxiliaryToolset() const
   if (version) {
     std::string instancePath;
     GetVSInstance(instancePath);
-    std::stringstream path;
-    path << instancePath;
-    path << "/VC/Auxiliary/Build";
-    path << (cmSystemTools::VersionCompareGreaterEq(version, "14.20") ? '.'
-                                                                      : '/');
-    path << version;
-    path << "/Microsoft.VCToolsVersion." << version << ".props";
-
-    std::string toolsetPath = path.str();
+    std::string toolsetDir = instancePath + "/VC/Auxiliary/Build";
+    char sep = '/';
+    if (cmSystemTools::VersionCompareGreaterEq(version, "14.20")) {
+      std::string toolsetDot = toolsetDir + "." + version +
+        "/Microsoft.VCToolsVersion." + version + ".props";
+      if (cmSystemTools::PathExists(toolsetDot)) {
+        sep = '.';
+      }
+    }
+    std::string toolsetPath = toolsetDir + sep + version +
+      "/Microsoft.VCToolsVersion." + version + ".props";
     cmSystemTools::ConvertToUnixSlashes(toolsetPath);
     return toolsetPath;
   }
-- 
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