Fix various errors found with UBSan

[damyanp]

• SPIRVOptions.h - one of the fields of this struct (signaturePacking) wasn't getting initialized before the struct's assignment operator was used. This resulted in the uninitialized fields being copied, which is UB. Although a more surgical fix is possible, it seemed better to just ensure all fields are initialized, setting a good precedent if any new fields are added.
• FrontendOptions.h - uninitialized field
• APInt.cpp - left shift of a signed integer
• Triple.h - uninitialized field
• VirtualFileSystem.h - uninitialized field
• Lookup.h - uninitialized field
• MemoryBuffer.cpp - avoid memcpy from a null dest (UB even if size is 0)

Methodology: had copilot CLI get a baseline running the tests under ubsan, categorize the failures and fix them, and verify that gcc-14 and clang 18 are now ubsan clan.

Co-authored-by: Copilot 223556219+Copilot@users.noreply.github.com

[github-actions]

⚠️ C/C++ code formatter, clang-format found issues in your code. ⚠️

You can test this locally with the following command:

git-clang-format --diff 02686effda507a065d729f402567af76b52485f4 26389eb8e88b966d3d6be13851069ef9dd599ea2 -- include/dxc/Support/SPIRVOptions.h include/llvm/ADT/Triple.h lib/Support/APInt.cpp lib/Support/MemoryBuffer.cpp tools/clang/include/clang/Basic/VirtualFileSystem.h tools/clang/include/clang/Frontend/FrontendOptions.h tools/clang/include/clang/Sema/Lookup.h

View the diff from clang-format here.

diff --git a/include/dxc/Support/SPIRVOptions.h b/include/dxc/Support/SPIRVOptions.h
index ede9fc0f..f39602e9 100644
--- a/include/dxc/Support/SPIRVOptions.h
+++ b/include/dxc/Support/SPIRVOptions.h
@@ -109,9 +109,11 @@ struct SpirvCodeGenOptions {
   std::optional<BindingInfo> samplerHeapBinding;
   std::optional<BindingInfo> counterHeapBinding;
 
-  bool signaturePacking = false; ///< Whether signature packing is enabled or not
+  bool signaturePacking =
+      false; ///< Whether signature packing is enabled or not
 
-  bool printAll = false; // Dump SPIR-V module before each pass and after the last one.
+  bool printAll =
+      false; // Dump SPIR-V module before each pass and after the last one.
 
   // String representation of all command line options and input file.
   std::string clOptions;
diff --git a/lib/Support/APInt.cpp b/lib/Support/APInt.cpp
index 8b80b7ef..df41e00e 100644
--- a/lib/Support/APInt.cpp
+++ b/lib/Support/APInt.cpp
@@ -552,8 +552,10 @@ bool APInt::ult(const APInt& RHS) const {
 bool APInt::slt(const APInt& RHS) const {
   assert(BitWidth == RHS.BitWidth && "Bit widths must be same for comparison");
   if (isSingleWord()) {
-    int64_t lhsSext = int64_t(uint64_t(VAL) << (64-BitWidth)) >> (64-BitWidth);
-    int64_t rhsSext = int64_t(uint64_t(RHS.VAL) << (64-BitWidth)) >> (64-BitWidth);
+    int64_t lhsSext =
+        int64_t(uint64_t(VAL) << (64 - BitWidth)) >> (64 - BitWidth);
+    int64_t rhsSext =
+        int64_t(uint64_t(RHS.VAL) << (64 - BitWidth)) >> (64 - BitWidth);
     return lhsSext < rhsSext;
   }
 
@@ -1061,8 +1063,8 @@ APInt APInt::ashr(unsigned shiftAmt) const {
       return APInt(BitWidth, 0); // undefined
     else {
       unsigned SignBit = APINT_BITS_PER_WORD - BitWidth;
-      return APInt(BitWidth,
-        (((int64_t(uint64_t(VAL) << SignBit) >> SignBit) >> shiftAmt)));
+      return APInt(BitWidth, (((int64_t(uint64_t(VAL) << SignBit) >> SignBit) >>
+                               shiftAmt)));
     }
   }
 
diff --git a/lib/Support/MemoryBuffer.cpp b/lib/Support/MemoryBuffer.cpp
index e28144ff..608bda74 100644
--- a/lib/Support/MemoryBuffer.cpp
+++ b/lib/Support/MemoryBuffer.cpp
@@ -127,7 +127,7 @@ MemoryBuffer::getMemBufferCopy(StringRef InputData, const Twine &BufferName) {
   if (!Buf)
     return nullptr;
   if (InputData.size())
-    memcpy(const_cast<char*>(Buf->getBufferStart()), InputData.data(),
+    memcpy(const_cast<char *>(Buf->getBufferStart()), InputData.data(),
            InputData.size());
   return Buf;
 }
diff --git a/tools/clang/include/clang/Frontend/FrontendOptions.h b/tools/clang/include/clang/Frontend/FrontendOptions.h
index ae83c231..dabf1a4b 100644
--- a/tools/clang/include/clang/Frontend/FrontendOptions.h
+++ b/tools/clang/include/clang/Frontend/FrontendOptions.h
@@ -92,7 +92,7 @@ class FrontendInputFile {
   bool IsSystem;
 
 public:
-  FrontendInputFile() : Buffer(nullptr), Kind(IK_None), IsSystem(false) { }
+  FrontendInputFile() : Buffer(nullptr), Kind(IK_None), IsSystem(false) {}
   FrontendInputFile(StringRef File, InputKind Kind, bool IsSystem = false)
     : File(File.str()), Buffer(nullptr), Kind(Kind), IsSystem(IsSystem) { }
   FrontendInputFile(llvm::MemoryBuffer *buffer, InputKind Kind,

• Check this box to apply formatting changes to this branch.

[tex3d]

LGTM.