Tolerate removed/replaced CMakeCache.txt with old CMakeFiles/

Users or scripts commonly remove or replace `CMakeCache.txt` without
also removing `CMakeFiles/`.  In this case the information saved in the
cache from platform information initialization is missing, so we need to
re-initialize it.  In such a case, remove the platform information
directory so that re-initialization will occur and restore needed
information to the cache.

Closes: #14820

1 files changed, 20 insertions, 0 deletions

diff --git a/Source/cmGlobalGenerator.cxx b/Source/cmGlobalGenerator.cxx
index fa447ff..2808051 100644
--- a/Source/cmGlobalGenerator.cxx
+++ b/Source/cmGlobalGenerator.cxx
@@ -50,6 +50,9 @@
 #include <cm_jsoncpp_writer.h>
 #endif
 
+const std::string kCMAKE_PLATFORM_INFO_INITIALIZED =
+  "CMAKE_PLATFORM_INFO_INITIALIZED";
+
 class cmInstalledFile;
 
 bool cmTarget::StrictTargetComparison::operator()(cmTarget const* t1,
@@ -428,6 +431,23 @@ void cmGlobalGenerator::EnableLanguage(
   // set the dir for parent files so they can be used by modules
   mf->AddDefinition("CMAKE_PLATFORM_INFO_DIR", rootBin.c_str());
 
+  if (!this->CMakeInstance->GetIsInTryCompile()) {
+    // Keep a mark in the cache to indicate that we've initialized the
+    // platform information directory.  If the platform information
+    // directory exists but the mark is missing then CMakeCache.txt
+    // has been removed or replaced without also removing the CMakeFiles/
+    // directory.  In this case remove the platform information directory
+    // so that it will be re-initialized and the relevant information
+    // restored in the cache.
+    if (cmSystemTools::FileIsDirectory(rootBin) &&
+        !mf->IsOn(kCMAKE_PLATFORM_INFO_INITIALIZED)) {
+      cmSystemTools::RemoveADirectory(rootBin);
+    }
+    this->GetCMakeInstance()->AddCacheEntry(
+      kCMAKE_PLATFORM_INFO_INITIALIZED, "1",
+      "Platform information initialized", cmStateEnums::INTERNAL);
+  }
+
   // find and make sure CMAKE_MAKE_PROGRAM is defined
   if (!this->FindMakeProgram(mf)) {
     return;