Add __cxa_current_exception_type for emscripten exceptions (#23739)

Fixes: #23734

Author: sbc100

src/lib/libexceptions.js

@@ -179,6 +179,14 @@ var LibraryExceptions = {
     return info.excPtr;
   },
 
+  __cxa_current_exception_type() {
+    if (!exceptionCaught.length) {
+      return 0;
+    }
+    var info = exceptionCaught[exceptionCaught.length - 1];
+    return info.get_type();
+  },
+
   __cxa_rethrow_primary_exception__deps: ['$ExceptionInfo', '$exceptionCaught', '__cxa_rethrow'],
   __cxa_rethrow_primary_exception: (ptr) => {
     if (!ptr) return;

src/lib/libsigs.js

@@ -218,6 +218,7 @@ sigs = {
   __call_sighandler__sig: 'vpi',
   __cxa_begin_catch__sig: 'pp',
   __cxa_call_unexpected__sig: 'vp',
+  __cxa_current_exception_type__sig: 'p',
   __cxa_current_primary_exception__sig: 'p',
   __cxa_end_catch__sig: 'v',
   __cxa_rethrow__sig: 'v',

test/test_other.py

@@ -9579,6 +9579,23 @@ def test_exceptions_rethrow_stack_trace_and_message(self):
                       expected_output=rethrow_stack_trace_checks, regex=True)
     self.assertNotContained('important_function', err)
 
+  @with_all_eh_sjlj
+  def test_cxa_current_exception_type(self):
+    create_file('main.cpp', r'''
+    #include <cstdio>
+    #include <stdexcept>
+    #include <typeinfo>
+    #include <cxxabi.h>
+
+    int main() {
+      try {
+        throw std::runtime_error("ERROR");
+      } catch (...) {
+        printf("__cxa_current_exception_type: %s\n", abi::__cxa_current_exception_type()->name());
+      }
+    }''')
+    self.do_runf('main.cpp', '__cxa_current_exception_type: St13runtime_error')
+
   @with_all_eh_sjlj
   def test_exceptions_exit_runtime(self):
     self.set_setting('EXIT_RUNTIME')