[EH] Remove 'terminating' from exception message (#17058)

 #17003 added "terminating" to exception messages, but some people might
want to use the message in non-terminating cases. This changes
`emscripten_format_exception` to `__get_exception_message`, and
separately adds `__get_terminating_exception_message`. Adds two
underscores not to clash with the global namespace.

`__get_exception_message` prints messages like
```
exception of type char
exception of type std::runtime_error: abc
exception of type myexception: My exception happened
```
`__get_terminating_exception_message` prints messages like
```
terminating with uncaught exception of type char
terminating with uncaught exception of type std::runtime_error: abc
terminating with uncaught exception of type myexception: My exception happened
```

Author: aheejin

emcc.py

@@ -2138,7 +2138,7 @@ def phase_linker_setup(options, state, newargs, user_settings):
   # TODO: Move this into the library JS file once it becomes possible.
   # See https://github.com/emscripten-core/emscripten/pull/15982
   if settings.INCLUDE_FULL_LIBRARY and not settings.DISABLE_EXCEPTION_CATCHING:
-    settings.EXPORTED_FUNCTIONS += ['_emscripten_format_exception', '_free']
+    settings.EXPORTED_FUNCTIONS += ['___get_exception_message', '_free']
 
   if settings.WASM_WORKERS:
     # TODO: After #15982 is resolved, these dependencies can be declared in library_wasm_worker.js

src/library_exceptions.js

@@ -392,9 +392,9 @@ var LibraryExceptions = {
   },
 
 #if !DISABLE_EXCEPTION_CATCHING
-  $formatException__deps: ['emscripten_format_exception', 'free'],
-  $formatException: function(excPtr) {
-    var utf8_addr = _emscripten_format_exception(excPtr);
+  $getExceptionMessage__deps: ['__get_exception_message', 'free'],
+  $getExceptionMessage: function(excPtr) {
+    var utf8_addr = ___get_exception_message(excPtr);
     var result = UTF8ToString(utf8_addr);
     _free(utf8_addr);
     return result;

system/lib/libcxxabi/src/cxa_exception_emscripten.cpp

@@ -24,7 +24,7 @@ cxa_exception_from_thrown_object(void* thrown_object) {
 
 extern "C" {
 
-char* emscripten_format_exception(void* thrown_object) {
+char* __get_exception_message(void* thrown_object, bool terminate=false) {
   __cxa_exception* exception_header =
     cxa_exception_from_thrown_object(thrown_object);
   const __shim_type_info* thrown_type =
@@ -45,19 +45,27 @@ char* emscripten_format_exception(void* thrown_object) {
     const char* what =
       static_cast<const std::exception*>(thrown_object)->what();
     asprintf(&result,
-             "terminating with uncaught exception of type %s: %s",
+             (terminate ? "terminating with uncaught exception of type %s: %s"
+                        : "exception of type %s: %s"),
              type_name,
              what);
   } else {
-    asprintf(
-      &result, "terminating with uncaught exception of type %s", type_name);
+    asprintf(&result,
+             (terminate ? "terminating with uncaught exception of type %s"
+                        : "exception of type %s"),
+             type_name);
   }
 
   if (demangled_buf) {
     free(demangled_buf);
   }
   return result;
 }
+
+char* __get_exception_terminate_message(void *thrown_object) {
+  return __get_exception_message(thrown_object, true);
+}
+
 }
 
 #endif // __USING_EMSCRIPTEN_EXCEPTIONS__

tests/test_core.py

@@ -1608,10 +1608,10 @@ def test_exceptions_rethrow_missing(self):
     self.do_runf('main.cpp', None, assert_returncode=NON_ZERO)
 
   @no_wasm64('MEMORY64 does not yet support exceptions')
-  def test_format_exception(self):
+  def test_exception_message(self):
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
-    self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$formatException', '__cxa_decrement_exception_refcount', '__cxa_increment_exception_refcount'])
-    self.set_setting('EXPORTED_FUNCTIONS', ['_main', 'formatException', '_emscripten_format_exception', '_free'])
+    self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$getExceptionMessage', '__cxa_decrement_exception_refcount', '__cxa_increment_exception_refcount'])
+    self.set_setting('EXPORTED_FUNCTIONS', ['_main', 'getExceptionMessage', '___get_exception_message', '_free'])
     self.maybe_closure()
     src = '''
       #include <emscripten.h>
@@ -1645,26 +1645,26 @@ class myexception : public exception {
           EM_ASM({
             for (let i = 1; i < 6; i++){
               try {
-                  Module["_throw_exc"](i);
+                  _throw_exc(i);
               } catch(p) {
                   // Because we are catching and handling the exception in JS, the normal
                   // exception catching C++ code doesn't kick in, so we need to make sure we free
                   // the exception, if necessary. By incrementing and decrementing the refcount
                   // we trigger the free'ing of the exception if its refcount was zero.
                   ___cxa_increment_exception_refcount(p);
-                  console.log(Module["formatException"](p).replace(/0x[0-9a-f]*/, "xxx"));
+                  console.log(getExceptionMessage(p));
                   ___cxa_decrement_exception_refcount(p);
               }
             }
           });
       }
     '''
     expected = '''\
-terminating with uncaught exception of type int
-terminating with uncaught exception of type char
-terminating with uncaught exception of type std::runtime_error: abc
-terminating with uncaught exception of type myexception: My exception happened
-terminating with uncaught exception of type char const*
+exception of type int
+exception of type char
+exception of type std::runtime_error: abc
+exception of type myexception: My exception happened
+exception of type char const*
 '''
 
     self.do_run(src, expected)