From 8f72fc1c2d485a2217de8ab9e2836154b5ef737b Mon Sep 17 00:00:00 2001
From: Copilot <198982749+Copilot@users.noreply.github.com>
Date: Fri, 28 Aug 2026 09:57:50 -0700
Subject: [PATCH] Fix crossgen2 rejecting input files with uppercase .DLL/.EXE
 extensions (#132857)
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`crossgen2` rejected input assemblies whose on-disk extension is
uppercase (`.DLL`/`.EXE`), which occurs on filesystems/network shares
that normalize casing (e.g. WinFsp/virtiofs). This is a regression from
`Microsoft.NETCore.App.Crossgen2` 10.0.5 → 10.0.9, breaking
`PublishReadyToRun` builds on affected volumes.

## Root Cause

`RunSingleCompilation` in `src/coreclr/tools/aot/crossgen2/Program.cs`
matched `Path.GetExtension(inFilePath)` against `.dll`/`.exe` using a
case-sensitive switch expression, throwing `CommandLineException` for
any other casing.

## Fix

- Replaced the switch expression with cascading `if`/`else if`
statements comparing the extension via
`StringComparison.OrdinalIgnoreCase`, so `.dll`, `.DLL`, `.Dll`, `.exe`,
`.EXE`, etc. are all accepted.

- Fixes #132554

---------

Co-authored-by: copilot-swe-agent[bot] <198982749+Copilot@users.noreply.github.com>
Co-authored-by: jtschuster <36744439+jtschuster@users.noreply.github.com>
---
 src/coreclr/tools/aot/crossgen2/Program.cs | 35 ++++++++++++----------
 1 file changed, 20 insertions(+), 15 deletions(-)

diff --git a/src/coreclr/tools/aot/crossgen2/Program.cs b/src/coreclr/tools/aot/crossgen2/Program.cs
index 691add6dd78b2a..ebd233ed68ff83 100644
--- a/src/coreclr/tools/aot/crossgen2/Program.cs
+++ b/src/coreclr/tools/aot/crossgen2/Program.cs
@@ -309,8 +309,8 @@ public int Run()
                 {
                     foreach (var inputFile in inputFilePaths)
                     {
-                        var tmpOutFile = inputFile.Value.Replace(".dll", ".ni.dll.tmp");
-                        var outFile = inputFile.Value.Replace(".dll", ".ni.dll");
+                        var tmpOutFile = GetNearOutputFilePath(inputFile.Value, temporary: true);
+                        var outFile = GetNearOutputFilePath(inputFile.Value, temporary: false);
                         Console.WriteLine($@"Moving R2R PE file: {tmpOutFile} to {outFile}");
                         System.IO.File.Move(tmpOutFile, outFile);
                     }
@@ -324,6 +324,23 @@ public int Run()
             return 0;
         }
 
+        private static string GetNearOutputFilePath(string inFilePath, bool temporary)
+        {
+            string inputFileExtension = Path.GetExtension(inFilePath);
+            if (inputFileExtension.Equals(".dll", StringComparison.OrdinalIgnoreCase))
+            {
+                return Path.ChangeExtension(inFilePath, temporary ? ".ni.dll.tmp" : ".ni.dll");
+            }
+            else if (inputFileExtension.Equals(".exe", StringComparison.OrdinalIgnoreCase))
+            {
+                return Path.ChangeExtension(inFilePath, temporary ? ".ni.exe.tmp" : ".ni.exe");
+            }
+            else
+            {
+                throw new CommandLineException(string.Format(SR.UnsupportedInputFileExtension, inputFileExtension));
+            }
+        }
+
         private void RunSingleCompilation(Dictionary<string, string> inFilePaths, InstructionSetSupport instructionSetSupport, string compositeRootPath, Dictionary<string, string> unrootedInputFilePaths, HashSet<ModuleDesc> versionBubbleModulesHash, ReadyToRunCompilerContext typeSystemContext, Logger logger)
         {
             //
@@ -332,19 +349,7 @@ private void RunSingleCompilation(Dictionary<string, string> inFilePaths, Instru
             var e = inFilePaths.GetEnumerator();
             e.MoveNext();
             string inFilePath = e.Current.Value;
-            string inputFileExtension = Path.GetExtension(inFilePath);
-            string nearOutFilePath = inputFileExtension switch
-            {
-                ".dll" => Path.ChangeExtension(inFilePath,
-                    _singleFileCompilation&& _inputBubble
-                        ? ".ni.dll.tmp"
-                        : ".ni.dll"),
-                ".exe" => Path.ChangeExtension(inFilePath,
-                    _singleFileCompilation && _inputBubble
-                        ? ".ni.exe.tmp"
-                        : ".ni.exe"),
-                _ => throw new CommandLineException(string.Format(SR.UnsupportedInputFileExtension, inputFileExtension))
-            };
+            string nearOutFilePath = GetNearOutputFilePath(inFilePath, temporary: _singleFileCompilation && _inputBubble);
 
             string outFile = _outNearInput ? nearOutFilePath : _outputFilePath;
             string dgmlLogFileName = Get(_command.DgmlLogFileName);