Restore MODE=dbg support

We recently broke MODE=dbg support when we added C++ exception support.
This change adds the missing UBSAN interfaces, needed to get it working
again. Some of the ASAN checking in the SJLJ guts needed to be disabled
since I doubt anyone's combined the two features until now.

Author: jart

libc/intrin/ubsan.c

@@ -112,6 +112,13 @@ struct UbsanOverflowData {
   struct UbsanTypeDescriptor *type;
 };
 
+struct UbsanDynamicTypeCacheMissData {
+  struct UbsanSourceLocation location;
+  struct UbsanTypeDescriptor *type;
+  void *TypeInfo;
+  unsigned char TypeCheckKind;
+};
+
 struct UbsanFloatCastOverflowData {
 #if __GNUC__ + 0 >= 6
   struct UbsanSourceLocation location;
@@ -145,6 +152,8 @@ upcast of\0\
 cast to virtual base of\0\
 \0";
 
+uintptr_t __ubsan_vptr_type_cache[128];
+
 static int __ubsan_bits(struct UbsanTypeDescriptor *t) {
   return 1 << (t->info >> 1);
 }
@@ -439,15 +448,22 @@ void __ubsan_handle_divrem_overflow_abort(
   __ubsan_handle_divrem_overflow(loc);
 }
 
+static bool HandleDynamicTypeCacheMiss(
+    struct UbsanDynamicTypeCacheMissData *data, uintptr_t ptr, uintptr_t hash) {
+  return false;  // TODO: implement me
+}
+
 void __ubsan_handle_dynamic_type_cache_miss(
-    const struct UbsanSourceLocation *loc) {
-  __ubsan_abort(loc, "dynamic type cache miss")();
-  __ubsan_unreachable();
+    struct UbsanDynamicTypeCacheMissData *data, uintptr_t ptr, uintptr_t hash) {
+  HandleDynamicTypeCacheMiss(data, ptr, hash);
 }
 
 void __ubsan_handle_dynamic_type_cache_miss_abort(
-    const struct UbsanSourceLocation *loc) {
-  __ubsan_handle_dynamic_type_cache_miss(loc);
+    struct UbsanDynamicTypeCacheMissData *data, uintptr_t ptr, uintptr_t hash) {
+  if (HandleDynamicTypeCacheMiss(data, ptr, hash)) {
+    __ubsan_abort(&data->location, "dynamic type cache miss")();
+    __ubsan_unreachable();
+  }
 }
 
 void __ubsan_handle_function_type_mismatch(

third_party/libcxxabi/cxa_personality.cc

@@ -202,7 +202,7 @@ enum
 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
 /// @param data reference variable holding memory pointer to decode from
 /// @returns decoded value
-static
+static dontasan
 uintptr_t
 readULEB128(const uint8_t** data)
 {
@@ -225,7 +225,7 @@ readULEB128(const uint8_t** data)
 /// @link http://dwarfstd.org/Dwarf4.pdf @unlink
 /// @param data reference variable holding memory pointer to decode from
 /// @returns decoded value
-static
+static dontasan
 intptr_t
 readSLEB128(const uint8_t** data)
 {
@@ -542,7 +542,7 @@ struct scan_results
 
 }  // unnamed namespace
 
-static
+static dontasan
 void
 set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
               const scan_results& results)
@@ -581,6 +581,7 @@ set_registers(_Unwind_Exception* unwind_exception, _Unwind_Context* context,
         _UA_CLEANUP_PHASE && !_UA_HANDLER_FRAME
 */
 
+dontasan
 static void scan_eh_tab(scan_results &results, _Unwind_Action actions,
                         bool native_exception,
                         _Unwind_Exception *unwind_exception,
@@ -911,6 +912,7 @@ static _Unwind_Reason_Code __gxx_personality_imp
 #else
 _LIBCXXABI_FUNC_VIS _Unwind_Reason_Code
 #ifdef __USING_SJLJ_EXCEPTIONS__
+dontasan
 __gxx_personality_sj0
 #elif defined(__MVS__)
 __zos_cxx_personality_v2

third_party/libunwind/README.cosmo

@@ -12,5 +12,8 @@ ORIGIN
   Date:   Tue, 28 Nov 2023 09:52:28 +0100
 
 LOCAL CHANGES
-  - Fixed `_Unwind_FunctionContext` struct to be ABI-compatible with code
-  generated by GCC.
+
+  - Fixed `_Unwind_FunctionContext` struct to be ABI-compatible with
+    code generated by GCC.
+
+  - Added `dontasan` annotations to functions that raised ASAN errors.

third_party/libunwind/Unwind-sjlj.c

@@ -105,15 +105,15 @@ __Unwind_SjLj_SetTopOfFunctionStack(struct _Unwind_FunctionContext *fc) {
 
 
 /// Called at start of each function that catches exceptions
-_LIBUNWIND_EXPORT void
+_LIBUNWIND_EXPORT void dontasan
 _Unwind_SjLj_Register(struct _Unwind_FunctionContext *fc) {
   fc->prev = __Unwind_SjLj_GetTopOfFunctionStack();
   __Unwind_SjLj_SetTopOfFunctionStack(fc);
 }
 
 
 /// Called at end of each function that catches exceptions
-_LIBUNWIND_EXPORT void
+_LIBUNWIND_EXPORT void dontasan
 _Unwind_SjLj_Unregister(struct _Unwind_FunctionContext *fc) {
   __Unwind_SjLj_SetTopOfFunctionStack(fc->prev);
 }
@@ -426,6 +426,7 @@ _LIBUNWIND_EXPORT uintptr_t _Unwind_GetGR(struct _Unwind_Context *context,
 
 
 /// Called by personality handler during phase 2 to alter register values.
+dontasan
 _LIBUNWIND_EXPORT void _Unwind_SetGR(struct _Unwind_Context *context, int index,
                                      uintptr_t new_value) {
   _LIBUNWIND_TRACE_API("_Unwind_SetGR(context=%p, reg=%d, value=0x%" PRIuPTR