Index: lld/ELF/Config.h
===================================================================
--- lld/ELF/Config.h
+++ lld/ELF/Config.h
@@ -14,6 +14,7 @@
 #include "llvm/ADT/DenseSet.h"
 #include "llvm/ADT/MapVector.h"
 #include "llvm/ADT/SetVector.h"
+#include "llvm/ADT/SmallSet.h"
 #include "llvm/ADT/StringRef.h"
 #include "llvm/ADT/StringSet.h"
 #include "llvm/BinaryFormat/ELF.h"
@@ -23,6 +24,7 @@
 #include "llvm/Support/Compiler.h"
 #include "llvm/Support/Compression.h"
 #include "llvm/Support/Endian.h"
+#include "llvm/Support/FileSystem.h"
 #include "llvm/Support/GlobPattern.h"
 #include "llvm/Support/PrettyStackTrace.h"
 #include <atomic>
@@ -453,6 +455,7 @@
   llvm::DenseMap<const Symbol *,
                  std::pair<const InputFile *, const InputFile *>>
       backwardReferences;
+  llvm::SmallSet<llvm::StringRef, 0> auxiliaryFiles;
   // True if SHT_LLVM_SYMPART is used.
   std::atomic<bool> hasSympart{false};
   // True if there are TLS IE relocations. Set DF_STATIC_TLS if -shared.
@@ -461,6 +464,8 @@
   std::atomic<bool> needsTlsLd{false};
 
   void reset();
+
+  llvm::raw_fd_ostream openAuxiliaryFile(llvm::StringRef, std::error_code &);
 };
 
 LLVM_LIBRARY_VISIBILITY extern Ctx ctx;
Index: lld/ELF/Driver.cpp
===================================================================
--- lld/ELF/Driver.cpp
+++ lld/ELF/Driver.cpp
@@ -107,6 +107,14 @@
   needsTlsLd.store(false, std::memory_order_relaxed);
 }
 
+llvm::raw_fd_ostream Ctx::openAuxiliaryFile(llvm::StringRef filename,
+                                            std::error_code &ec) {
+  using namespace llvm::sys::fs;
+  OpenFlags flags =
+      auxiliaryFiles.insert(filename).second ? OF_None : OF_Append;
+  return {filename, ec, flags};
+}
+
 namespace lld {
 namespace elf {
 bool link(ArrayRef<const char *> args, llvm::raw_ostream &stdoutOS,
@@ -1957,7 +1965,7 @@
     return;
 
   std::error_code ec;
-  raw_fd_ostream os(config->printArchiveStats, ec, sys::fs::OF_None);
+  raw_fd_ostream os = ctx.openAuxiliaryFile(config->printArchiveStats, ec);
   if (ec) {
     error("--print-archive-stats=: cannot open " + config->printArchiveStats +
           ": " + ec.message());
@@ -1987,7 +1995,7 @@
     return;
 
   std::error_code ec;
-  raw_fd_ostream os(config->whyExtract, ec, sys::fs::OF_None);
+  raw_fd_ostream os = ctx.openAuxiliaryFile(config->whyExtract, ec);
   if (ec) {
     error("cannot open --why-extract= file " + config->whyExtract + ": " +
           ec.message());
@@ -2046,7 +2054,7 @@
 // easily.
 static void writeDependencyFile() {
   std::error_code ec;
-  raw_fd_ostream os(config->dependencyFile, ec, sys::fs::OF_None);
+  raw_fd_ostream os = ctx.openAuxiliaryFile(config->dependencyFile, ec);
   if (ec) {
     error("cannot open " + config->dependencyFile + ": " + ec.message());
     return;
Index: lld/ELF/MapFile.cpp
===================================================================
--- lld/ELF/MapFile.cpp
+++ lld/ELF/MapFile.cpp
@@ -263,7 +263,7 @@
   // Open a map file for writing.
   std::error_code ec;
   StringRef mapFile = config->mapFile.empty() ? "-" : config->mapFile;
-  raw_fd_ostream os(mapFile, ec, sys::fs::OF_None);
+  raw_fd_ostream os = ctx.openAuxiliaryFile(mapFile, ec);
   if (ec) {
     error("cannot open " + mapFile + ": " + ec.message());
     return;
Index: lld/test/ELF/diagnostic-options.test
===================================================================
--- /dev/null
+++ lld/test/ELF/diagnostic-options.test
@@ -0,0 +1,19 @@
+# RUN: ld.lld -o /dev/null -shared /dev/null -m elf_x86_64 \
+# RUN:   --print-archive-stats=%t --why-extract=%t --dependency-file=%t -Map=%t
+# RUN: FileCheck --input-file=%t %s
+
+# RUN: ld.lld -o /dev/null -shared /dev/null -m elf_x86_64 \
+# RUN:   --print-archive-stats=- --why-extract=- --dependency-file=- -Map=- \
+# RUN:   | FileCheck %s
+
+## From --print-archive-stats
+# CHECK: members extracted archive
+
+## From --why-extract
+# CHECK: reference extracted symbol
+
+## From --dependency-file
+# CHECK: /dev/null: \
+
+## From -Map
+# CHECK: VMA LMA Size