cmake: Avoid initializing with empty source and build paths

Source/cmGlobalNinjaGenerator.cxx

@@ -2994,9 +2994,33 @@ int cmcmd_cmake_ninja_dyndep(std::vector<std::string>::const_iterator argBeg,
   }
 
   std::string const dir_cur_bld = tdi["dir-cur-bld"].asString();
+  if (!cmSystemTools::FileIsFullPath(dir_cur_bld)) {
+    cmSystemTools::Error(
+      "-E cmake_ninja_dyndep --tdi= file has no absolute dir-cur-bld");
+    return 1;
+  }
+
   std::string const dir_cur_src = tdi["dir-cur-src"].asString();
+  if (!cmSystemTools::FileIsFullPath(dir_cur_src)) {
+    cmSystemTools::Error(
+      "-E cmake_ninja_dyndep --tdi= file has no absolute dir-cur-src");
+    return 1;
+  }
+
   std::string const dir_top_bld = tdi["dir-top-bld"].asString();
+  if (!cmSystemTools::FileIsFullPath(dir_top_bld)) {
+    cmSystemTools::Error(
+      "-E cmake_ninja_dyndep --tdi= file has no absolute dir-top-bld");
+    return 1;
+  }
+
   std::string const dir_top_src = tdi["dir-top-src"].asString();
+  if (!cmSystemTools::FileIsFullPath(dir_top_src)) {
+    cmSystemTools::Error(
+      "-E cmake_ninja_dyndep --tdi= file has no absolute dir-top-src");
+    return 1;
+  }
+
   std::string module_dir = tdi["module-dir"].asString();
   if (!module_dir.empty() && !cmHasLiteralSuffix(module_dir, "/")) {
     module_dir += '/';

Source/cmake.cxx

@@ -4,6 +4,7 @@
 
 #include <algorithm>
 #include <array>
+#include <cassert>
 #include <chrono>
 #include <cstdio>
 #include <cstdlib>
@@ -1889,7 +1890,7 @@ bool cmake::SetDirectoriesFromFile(std::string const& arg)
     if (this->LoadCache(cachePath)) {
       cmValue existingValue =
         this->State->GetCacheEntryValue("CMAKE_HOME_DIRECTORY");
-      if (existingValue) {
+      if (existingValue && !existingValue.IsEmpty()) {
         this->SetHomeOutputDirectory(cachePath);
         this->SetHomeDirectory(*existingValue);
         return true;
@@ -2147,6 +2148,7 @@ void cmake::SetHomeDirectoryViaCommandLine(std::string const& path)
 
 void cmake::SetHomeDirectory(std::string const& dir)
 {
+  assert(!dir.empty());
   this->State->SetSourceDirectory(dir);
   if (this->CurrentSnapshot.IsValid()) {
     this->CurrentSnapshot.SetDefinition("CMAKE_SOURCE_DIR", dir);
@@ -2166,6 +2168,7 @@ std::string const& cmake::GetHomeDirectory() const
 
 void cmake::SetHomeOutputDirectory(std::string const& dir)
 {
+  assert(!dir.empty());
   this->State->SetBinaryDirectory(dir);
   if (this->CurrentSnapshot.IsValid()) {
     this->CurrentSnapshot.SetDefinition("CMAKE_BINARY_DIR", dir);