Graphviz: Fix issue with too many open file streams on Windows platform

Fixes #20931

Source/cmGraphVizWriter.cxx

@@ -125,14 +125,6 @@ cmGraphVizWriter::cmGraphVizWriter(std::string const& fileName,
 cmGraphVizWriter::~cmGraphVizWriter()
 {
   this->WriteFooter(this->GlobalFileStream);
-
-  for (auto& fileStream : this->PerTargetFileStreams) {
-    this->WriteFooter(*fileStream.second);
-  }
-
-  for (auto& fileStream : this->TargetDependersFileStreams) {
-    this->WriteFooter(*fileStream.second);
-  }
 }
 
 void cmGraphVizWriter::VisitGraph(std::string const&)
@@ -151,20 +143,10 @@ void cmGraphVizWriter::OnItem(cmLinkItem const& item)
   ++NextNodeId;
 
   this->WriteNode(this->GlobalFileStream, item);
-
-  if (this->GeneratePerTarget) {
-    this->CreateTargetFile(this->PerTargetFileStreams, item);
-  }
-
-  if (this->GenerateDependers) {
-    this->CreateTargetFile(this->TargetDependersFileStreams, item,
-                           ".dependers");
-  }
 }
 
-void cmGraphVizWriter::CreateTargetFile(FileStreamMap& fileStreamMap,
-                                        cmLinkItem const& item,
-                                        std::string const& fileNameSuffix)
+std::unique_ptr<cmGeneratedFileStream> cmGraphVizWriter::CreateTargetFile(
+  cmLinkItem const& item, std::string const& fileNameSuffix)
 {
   auto const pathSafeItemName = PathSafeString(item.AsStr());
   auto const perTargetFileName =
@@ -175,7 +157,7 @@ void cmGraphVizWriter::CreateTargetFile(FileStreamMap& fileStreamMap,
   this->WriteHeader(*perTargetFileStream, item.AsStr());
   this->WriteNode(*perTargetFileStream, item);
 
-  fileStreamMap.emplace(item.AsStr(), std::move(perTargetFileStream));
+  return perTargetFileStream;
 }
 
 void cmGraphVizWriter::OnDirectLink(cmLinkItem const& depender,
@@ -323,13 +305,12 @@ void cmGraphVizWriter::Write()
   }
 
   if (this->GeneratePerTarget) {
-    WritePerTargetConnections<DependeesDir>(PerTargetConnections,
-                                            PerTargetFileStreams);
+    WritePerTargetConnections<DependeesDir>(PerTargetConnections);
   }
 
   if (this->GenerateDependers) {
     WritePerTargetConnections<DependersDir>(TargetDependersConnections,
-                                            TargetDependersFileStreams);
+                                            ".dependers");
   }
 }
 
@@ -368,7 +349,7 @@ void cmGraphVizWriter::FindAllConnections(const ConnectionsMap& connectionMap,
 
 template <typename DirFunc>
 void cmGraphVizWriter::WritePerTargetConnections(
-  const ConnectionsMap& connections, const FileStreamMap& streams)
+  const ConnectionsMap& connections, const std::string& fileNameSuffix)
 {
   // the per target connections must be extended by indirect dependencies
   ConnectionsMap extendedConnections;
@@ -387,7 +368,9 @@ void cmGraphVizWriter::WritePerTargetConnections(
     }
 
     const Connections& cons = conPerTarget.second;
-    auto fileStream = streams.at(rootItem.AsStr()).get();
+
+    std::unique_ptr<cmGeneratedFileStream> fileStream =
+      this->CreateTargetFile(rootItem, fileNameSuffix);
 
     for (const Connection& con : cons) {
       const cmLinkItem& src = DirFunc::src(con);
@@ -395,6 +378,8 @@ void cmGraphVizWriter::WritePerTargetConnections(
       this->WriteNode(*fileStream, con.dst);
       this->WriteConnection(*fileStream, src, dst, con.scopeType);
     }
+
+    this->WriteFooter(*fileStream);
   }
 }
 

Source/cmGraphVizWriter.h

@@ -46,9 +46,6 @@ public:
   void Write();
 
 private:
-  using FileStreamMap =
-    std::map<std::string, std::unique_ptr<cmGeneratedFileStream>>;
-
   struct Connection
   {
     Connection(cmLinkItem s, cmLinkItem d, std::string scope)
@@ -76,8 +73,8 @@ private:
 
   void WriteNode(cmGeneratedFileStream& fs, cmLinkItem const& item);
 
-  void CreateTargetFile(FileStreamMap& fileStreamMap, cmLinkItem const& target,
-                        std::string const& fileNameSuffix = "");
+  std::unique_ptr<cmGeneratedFileStream> CreateTargetFile(
+    cmLinkItem const& target, std::string const& fileNameSuffix = "");
 
   void WriteConnection(cmGeneratedFileStream& fs,
                        cmLinkItem const& dependerTargetName,
@@ -95,7 +92,7 @@ private:
 
   template <typename DirFunc>
   void WritePerTargetConnections(const ConnectionsMap& connections,
-                                 const FileStreamMap& streams);
+                                 const std::string& fileNameSuffix = "");
 
   bool ItemExcluded(cmLinkItem const& item);
   bool ItemNameFilteredOut(std::string const& itemName);
@@ -111,8 +108,6 @@ private:
 
   std::string FileName;
   cmGeneratedFileStream GlobalFileStream;
-  FileStreamMap PerTargetFileStreams;
-  FileStreamMap TargetDependersFileStreams;
 
   ConnectionsMap PerTargetConnections;
   ConnectionsMap TargetDependersConnections;