cmOutputConverter: Reduce string copies in ConvertToOutputForExisting

Allocate only when actually converting to a short path.

Source/cmOutputConverter.cxx

@@ -155,44 +155,36 @@ std::string cmOutputConverter::MaybeRelativeToCurBinDir(
 }
 
 std::string cmOutputConverter::ConvertToOutputForExisting(
-  std::string const& remote, OutputFormat format, bool useWatcomQuote) const
+  cm::string_view path, OutputFormat format, bool useWatcomQuote) const
 {
 #ifdef _WIN32
-  // Cache the Short Paths since we only convert the same few paths anyway and
-  // calling `GetShortPathNameW` is really expensive.
+  // Cache the short paths since `GetShortPathNameW` is really expensive.
   static std::unordered_map<std::string, std::string> shortPathCache{};
 
-  // If this is a windows shell, the result has a space, and the path
-  // already exists, we can use a short-path to reference it without a
-  // space.
+  // If this is a windows shell, the path has a space, and the path already
+  // exists, we can use a short-path to reference it without a space.
   if (this->GetState()->UseWindowsShell() &&
-      remote.find_first_of(" #") != std::string::npos &&
-      cmSystemTools::FileExists(remote)) {
-
-    std::string shortPath = [&]() {
-      auto cachedShortPathIt = shortPathCache.find(remote);
-
-      if (cachedShortPathIt != shortPathCache.end()) {
-        return cachedShortPathIt->second;
+      path.find_first_of(" #") != std::string::npos) {
+    auto origPath = std::string(path);
+    if (cmSystemTools::FileExists(origPath)) {
+      auto i = shortPathCache.find(origPath);
+      if (i == shortPathCache.end()) {
+        std::string shortPath;
+        if (!cmSystemTools::GetShortPath(origPath, shortPath)) {
+          // Fallback for cases when Windows refuses to resolve
+          // the short path, like for `C:\Program Files\WindowsApps\...`.
+          shortPath = origPath;
+        }
+        i = shortPathCache.emplace(std::move(origPath), std::move(shortPath))
+              .first;
       }
-
-      std::string tmp{};
-      cmsys::Status status = cmSystemTools::GetShortPath(remote, tmp);
-      if (!status) {
-        // Fallback for cases when Windows refuses to resolve the short path,
-        // like for C:\Program Files\WindowsApps\...
-        tmp = remote;
-      }
-      shortPathCache[remote] = tmp;
-      return tmp;
-    }();
-
-    return this->ConvertToOutputFormat(shortPath, format, useWatcomQuote);
+      path = i->second;
+    }
   }
 #endif
 
   // Otherwise, perform standard conversion.
-  return this->ConvertToOutputFormat(remote, format, useWatcomQuote);
+  return this->ConvertToOutputFormat(path, format, useWatcomQuote);
 }
 
 std::string cmOutputConverter::ConvertToOutputFormat(cm::string_view source,

Source/cmOutputConverter.h

@@ -54,7 +54,7 @@ public:
   std::string ConvertDirectorySeparatorsForShell(cm::string_view source) const;
 
   //! for existing files convert to output path and short path if spaces
-  std::string ConvertToOutputForExisting(std::string const& remote,
+  std::string ConvertToOutputForExisting(cm::string_view path,
                                          OutputFormat format = SHELL,
                                          bool useWatcomQuote = false) const;