[ci] Add ubsan support (#917)

* [ci] Add ubsan support

* [test] Bury Interpreter to avoid LSan noise from CppInterOp#887.

Interpreter_ExternalInterpreter intentionally gives up ownership of
its std::unique_ptr<Interpreter> because running the destructor trips
the teardown-order issue tracked in CppInterOp#887. The bare release()
leaves the pointer unreachable at exit, so LSan classified the whole
CompilerInstance graph (IdentifierTable, Preprocessor, Builtin
identifiers, JIT modules) as ~1 MB of leaks across ~1000 allocations
in the ASan+UBSan sanitizer job.

Switch release() to llvm::BuryPointer, which parks the pointer in a
static GraveYard so LSan sees the graph as reachable via that global.
The Interpreter still lives for program lifetime; only the LSan
classification changes.

Author: vgvassilev

.github/workflows/main.yml

@@ -82,13 +82,13 @@ jobs:
             clang-runtime: '22'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
-          - name: ubu24-x86-gcc12-clang-repl-22-asan
+          - name: ubu24-x86-clang22-clang-repl-22-asan-ubsan
             os: ubuntu-24.04
-            compiler: gcc-12
+            compiler: clang-22
             clang-runtime: '22'
             llvm_enable_projects: "clang"
             llvm_targets_to_build: "host;NVPTX"
-            sanitizer: "Address"
+            sanitizer: "Address;Undefined"
             python-version: '3.14'
           - name: ubu24-x86-gcc12-clang-repl-21-cppyy
             os: ubuntu-24.04

unittests/CppInterOp/InterpreterTest.cpp

@@ -18,6 +18,7 @@
 
 #include "llvm/ADT/SmallString.h"
 #include "llvm/Config/llvm-config.h"
+#include "llvm/Support/BuryPointer.h"
 #include "llvm/Support/FileSystem.h"
 #include "llvm/Support/Path.h"
 
@@ -466,7 +467,10 @@ TYPED_TEST(CPPINTEROP_TEST_MODE, Interpreter_ExternalInterpreter) {
   EXPECT_TRUE(Cpp::GetInterpreter()) << "External Interpreter not set";
 
 #ifndef CPPINTEROP_USE_CLING
-  I.release();
+  // Skip Interpreter destruction: the teardown-order bug tracked in
+  // CppInterOp#887 makes it unsafe. BuryPointer is used instead of
+  // release() so LSan sees the graph as reachable rather than leaked.
+  llvm::BuryPointer(std::move(I));
 #endif
 
 #ifdef CPPINTEROP_USE_CLING