[clang] [clang][Dependency Scanning] Canonicalize Defines of a Compiler Invocation As Early As Possible (PR #159620)

[Qiongsi Wu via cfe-commits]

https://github.com/qiongsiwu updated https://github.com/llvm/llvm-project/pull/159620

>From 250d52ddcafee193a987b9dde639ab2cd5aa81e7 Mon Sep 17 00:00:00 2001
From: Qiongsi Wu <qiongsi_wu at apple.com>
Date: Thu, 18 Sep 2025 11:04:37 -0700
Subject: [PATCH] Making sure the scanning `CompilerInvocation`'s `-D`s are
 canonicalized.

---
 .../DependencyScanning/DependencyScanningWorker.cpp        | 7 +++++--
 1 file changed, 5 insertions(+), 2 deletions(-)

diff --git a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
index 0855e6dec6158..f2bd5a0c767a1 100644
--- a/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
+++ b/clang/lib/Tooling/DependencyScanning/DependencyScanningWorker.cpp
@@ -391,10 +391,13 @@ class DependencyScanningAction {
                      IntrusiveRefCntPtr<llvm::vfs::FileSystem> FS,
                      std::shared_ptr<PCHContainerOperations> PCHContainerOps,
                      DiagnosticConsumer *DiagConsumer) {
+    // Making sure that we canonicalize the defines before we create the deep
+    // copy.
+    if (any(Service.getOptimizeArgs() & ScanningOptimizations::Macros))
+      canonicalizeDefines(Invocation->getPreprocessorOpts());
+
     // Make a deep copy of the original Clang invocation.
     CompilerInvocation OriginalInvocation(*Invocation);
-    if (any(Service.getOptimizeArgs() & ScanningOptimizations::Macros))
-      canonicalizeDefines(OriginalInvocation.getPreprocessorOpts());
 
     if (Scanned) {
       // Scanning runs once for the first -cc1 invocation in a chain of driver