[clang] 295b0ef - [C++20][Modules] Fix relocatable PCH feature. (#180023)

[via cfe-commits]

Author: Michael Park
Date: 2026-02-05T22:04:54-08:00
New Revision: 295b0ef7b9aa345867e458912c8ade3f55a41f99

URL: https://github.com/llvm/llvm-project/commit/295b0ef7b9aa345867e458912c8ade3f55a41f99
DIFF: https://github.com/llvm/llvm-project/commit/295b0ef7b9aa345867e458912c8ade3f55a41f99.diff

LOG: [C++20][Modules] Fix relocatable PCH feature. (#180023)

Added: 
    

Modified: 
    clang/lib/Serialization/ASTWriter.cpp
    clang/test/PCH/reloc.c

Removed: 
    


################################################################################
diff  --git a/clang/lib/Serialization/ASTWriter.cpp b/clang/lib/Serialization/ASTWriter.cpp
index 3e10bbfedfe65..b55440b4a4f39 100644
--- a/clang/lib/Serialization/ASTWriter.cpp
+++ b/clang/lib/Serialization/ASTWriter.cpp
@@ -1526,10 +1526,12 @@ void ASTWriter::WriteControlBlock(Preprocessor &PP, StringRef isysroot) {
 
       // Write out all other paths relative to the base directory if possible.
       BaseDirectory.assign(BaseDir->begin(), BaseDir->end());
-    } else if (!isysroot.empty()) {
-      // Write out paths relative to the sysroot if possible.
-      BaseDirectory = std::string(isysroot);
     }
+  } else if (!isysroot.empty()) {
+    // Write out paths relative to the sysroot if possible.
+    SmallString<128> CleanedSysroot(isysroot);
+    cleanPathForOutput(PP.getFileManager(), CleanedSysroot);
+    BaseDirectory.assign(CleanedSysroot.begin(), CleanedSysroot.end());
   }
 
   // Module map file

diff  --git a/clang/test/PCH/reloc.c b/clang/test/PCH/reloc.c
index 435fde2e19234..019e3c495218b 100644
--- a/clang/test/PCH/reloc.c
+++ b/clang/test/PCH/reloc.c
@@ -3,6 +3,11 @@
 // RUN: %clang -target x86_64-apple-darwin11 -fsyntax-only \
 // RUN:   -include-pch %t -isysroot %S/Inputs/libroot %s -Xclang -verify
 // RUN: not %clang -target x86_64-apple-darwin11 -include-pch %t %s
+// RUN: llvm-bcanalyzer --dump --disable-histogram %t \
+// RUN:   | FileCheck %s
+// CHECK: <ORIGINAL_FILE {{.*}}/> blob data = 'usr{{[/\\]}}include{{[/\\]}}reloc.h'
+// CHECK: <INPUT_FILE {{.*}}/> blob data = 'usr{{[/\\]}}include{{[/\\]}}reloc.h'
+// CHECK: <INPUT_FILE {{.*}}/> blob data = 'usr{{[/\\]}}include{{[/\\]}}reloc2.h'
 // REQUIRES: x86-registered-target
 
 #include <reloc.h>