[clang] 77bdc16 - [dyndbg][Clang] Avoid memcpy on nullptr from #216307 (#216625)

[via cfe-commits]

Author: Thurston Dang
Date: 2026-08-16T20:56:28-07:00
New Revision: 77bdc160b4ae80a4a887e927afb2934a6b417d41

URL: https://github.com/llvm/llvm-project/commit/77bdc160b4ae80a4a887e927afb2934a6b417d41
DIFF: https://github.com/llvm/llvm-project/commit/77bdc160b4ae80a4a887e927afb2934a6b417d41.diff

LOG: [dyndbg][Clang] Avoid memcpy on nullptr from #216307 (#216625)

As reported in
https://github.com/llvm/llvm-project/pull/216307#issuecomment-5311023374,
the new tests fail on UBSan buildbots (e.g.,
https://lab.llvm.org/buildbot/#/builders/25/builds/19323) because the
directory may be empty (only the file is initialized [*]). The StringRef
from getDirectory() would be default-initialized, and hashing it results
in memcpy'ing from a null pointer.

This patch attempts to fix-forward by not hashing the output of
getDirectory() if it is empty.

[*] e.g., `!3 = !DIFile(filename:
"/usr/local/google/home/thurston/llvm-projectA/clang/test/DebugInfo/DynamicDebugging/<stdin>",
directory: "")`

Added: 
    

Modified: 
    clang/lib/CodeGen/BackendUtil.cpp

Removed: 
    


################################################################################
diff  --git a/clang/lib/CodeGen/BackendUtil.cpp b/clang/lib/CodeGen/BackendUtil.cpp
index 75c3d16e455f1..e55d242cde68a 100644
--- a/clang/lib/CodeGen/BackendUtil.cpp
+++ b/clang/lib/CodeGen/BackendUtil.cpp
@@ -1527,7 +1527,9 @@ static void createAndEmbedModuleForDynamicDebugging(
     // the same source file compiled twice won't generate unique hashes.
     Hash.update(CGOpts.CmdArgs);
     for (auto *CU : M->debug_compile_units()) {
-      Hash.update(CU->getDirectory());
+      if (CU->getDirectory().size() > 0)
+        Hash.update(CU->getDirectory());
+
       Hash.update(CU->getFilename());
     }