build: add ubsan default options

Use print_stacktrace=1 for UBSAN by default.

src/nvim/CMakeLists.txt

@@ -836,6 +836,7 @@ if(ENABLE_ASAN_UBSAN)
     -fsanitize=address
     -fsanitize=undefined)
   target_link_libraries(nvim PRIVATE -fsanitize=address -fsanitize=undefined)
+  target_compile_definitions(nvim PRIVATE ENABLE_ASAN_UBSAN)
 elseif(ENABLE_MSAN)
   message(STATUS "Enabling memory sanitizer for nvim.")
   target_compile_options(nvim PRIVATE

src/nvim/README.md

@@ -71,9 +71,8 @@ Create a directory to store logs:
 Configure the sanitizer(s) via these environment variables:
 
     # Change to detect_leaks=1 to detect memory leaks (slower, noisier).
-    export ASAN_OPTIONS="detect_leaks=0:log_path=$HOME/logs/asan,handle_abort=1,handle_sigill=1"
+    export ASAN_OPTIONS="detect_leaks=0:log_path=$HOME/logs/asan"
     # Show backtraces in the logs.
-    export UBSAN_OPTIONS=print_stacktrace=1
     export MSAN_OPTIONS="log_path=${HOME}/logs/msan"
     export TSAN_OPTIONS="log_path=${HOME}/logs/tsan"
 

src/nvim/main.c

@@ -2222,3 +2222,17 @@ static void check_swap_exists_action(void)
   }
   handle_swap_exists(NULL);
 }
+
+#ifdef ENABLE_ASAN_UBSAN
+const char *__ubsan_default_options(void);
+const char *__ubsan_default_options(void)
+{
+  return "print_stacktrace=1";
+}
+
+const char *__asan_default_options(void);
+const char *__asan_default_options(void)
+{
+  return "handle_abort=1,handle_sigill=1";
+}
+#endif