Move __cxa_get_exception_ptr to native code. NFC (#22421)

The removes the need to for the `__cxa_is_pointer_type` export which is
now just part of `__cxa_get_exception_ptr`.

Author: sbc100

src/library_exceptions.js

@@ -20,12 +20,9 @@ var LibraryExceptions = {
   // reference counter) is not protected from that. Also protection is not enough, separate state
   // should be allocated. libcxxabi has concept of dependent exception which is used for that
   // purpose, it references the primary exception.
-  $ExceptionInfo__deps: [
-    '__cxa_is_pointer_type',
 #if EXCEPTION_DEBUG
-    '$ptrToString'
+  $ExceptionInfo__deps: ['$ptrToString'],
 #endif
-  ],
   $ExceptionInfo: class {
     // excPtr - Thrown object pointer to wrap. Metadata pointer is calculated from it.
     constructor(excPtr) {
@@ -84,22 +81,6 @@ var LibraryExceptions = {
     get_adjusted_ptr() {
       return {{{ makeGetValue('this.ptr', C_STRUCTS.__cxa_exception.adjustedPtr, '*') }}};
     }
-
-    // Get pointer which is expected to be received by catch clause in C++ code. It may be adjusted
-    // when the pointer is casted to some of the exception object base classes (e.g. when virtual
-    // inheritance is used). When a pointer is thrown this method should return the thrown pointer
-    // itself.
-    get_exception_ptr() {
-      // Work around a fastcomp bug, this code is still included for some reason in a build without
-      // exceptions support.
-      var isPointer = ___cxa_is_pointer_type(this.get_type());
-      if (isPointer) {
-        return {{{ makeGetValue('this.excPtr', '0', '*') }}};
-      }
-      var adjusted = this.get_adjusted_ptr();
-      if (adjusted !== 0) return adjusted;
-      return this.excPtr;
-    }
   },
 
   // Here, we throw an exception after recording a couple of values that we need to remember
@@ -146,6 +127,7 @@ var LibraryExceptions = {
 
 #if !DISABLE_EXCEPTION_CATCHING
   __cxa_begin_catch__deps: ['$exceptionCaught', '__cxa_increment_exception_refcount',
+                            '__cxa_get_exception_ptr',
                             '$uncaughtExceptionCount'],
   __cxa_begin_catch: (ptr) => {
     var info = new ExceptionInfo(ptr);
@@ -158,8 +140,8 @@ var LibraryExceptions = {
 #if EXCEPTION_DEBUG
     dbg('__cxa_begin_catch ' + [ptrToString(ptr), 'stack', exceptionCaught]);
 #endif
-    ___cxa_increment_exception_refcount(info.excPtr);
-    return info.get_exception_ptr();
+    ___cxa_increment_exception_refcount(ptr);
+    return ___cxa_get_exception_ptr(ptr);
   },
 
   // We're done with a catch. Now, we can run the destructor if there is one
@@ -183,15 +165,6 @@ var LibraryExceptions = {
     exceptionLast = 0; // XXX in decRef?
   },
 
-  __cxa_get_exception_ptr__deps: ['$ExceptionInfo'],
-  __cxa_get_exception_ptr: (ptr) => {
-    var rtn = new ExceptionInfo(ptr).get_exception_ptr();
-#if EXCEPTION_DEBUG
-    dbg('__cxa_get_exception_ptr ' + ptrToString(ptr) + ' -> ' + ptrToString(rtn));
-#endif
-    return rtn;
-  },
-
   __cxa_uncaught_exceptions__deps: ['$uncaughtExceptionCount'],
   __cxa_uncaught_exceptions: () => uncaughtExceptionCount,
 

src/library_sigs.js

@@ -220,7 +220,6 @@ sigs = {
   __cxa_call_unexpected__sig: 'vp',
   __cxa_current_primary_exception__sig: 'p',
   __cxa_end_catch__sig: 'v',
-  __cxa_get_exception_ptr__sig: 'pp',
   __cxa_rethrow__sig: 'v',
   __cxa_rethrow_primary_exception__sig: 'vp',
   __cxa_throw__sig: 'vppp',

system/lib/libcxxabi/src/cxa_exception_emscripten.cpp

@@ -17,9 +17,14 @@
 #include "cxa_exception.h"
 #include "include/atomic_support.h"
 #include "fallback_malloc.h"
+#include "private_typeinfo.h"
 #include "stdio.h"
 #include "assert.h"
 
+#ifdef __WASM_EXCEPTIONS__
+#error "This file should only be included when building with emscripten exceptions"
+#endif
+
 // Define to enable extra debugging on stderr.
 #if EXCEPTIONS_DEBUG
 #include "emscripten/console.h"
@@ -109,6 +114,26 @@ void __cxa_free_exception(void *thrown_object) throw() {
     __aligned_free_with_fallback((void *)raw_buffer);
 }
 
+void *__cxa_get_exception_ptr(void *thrown_object) throw() {
+    // Get pointer which is expected to be received by catch clause in C++ code.
+    // It may be adjusted when the pointer is casted to some of the exception
+    // object base classes (e.g. when virtual inheritance is used). When a pointer
+    // is thrown this method should return the thrown pointer itself.
+    // Work around a fastcomp bug, this code is still included for some reason in
+    // a build without exceptions support.
+    __cxa_exception* ex = cxa_exception_from_thrown_object(thrown_object);
+    bool is_pointer = !!dynamic_cast<__pointer_type_info*>(ex->exceptionType);
+    void* rtn;
+    if (is_pointer)
+        rtn = *(void**)thrown_object;
+    else if (ex->adjustedPtr)
+        rtn = ex->adjustedPtr;
+    else
+        rtn = ex;
+    DEBUG("__cxa_get_exception_ptr %p -> %p\n", thrown_object, rtn);
+    return rtn;
+}
+
 /*
     If thrown_object is not null, atomically increment the referenceCount field
     of the __cxa_exception header associated with the thrown object referred to

system/lib/libcxxabi/src/private_typeinfo.cpp

@@ -1555,10 +1555,6 @@ int __cxa_can_catch(__shim_type_info* catchType, __shim_type_info* excpType, voi
   return ret;
 }
 
-int __cxa_is_pointer_type(__shim_type_info* type) {
-  return !!dynamic_cast<__pointer_type_info*>(type);
-}
-
 }
 #endif // __EMSCRIPTEN_EXCEPTIONS__
 

test/code_size/embind_hello_wasm.json

@@ -3,8 +3,8 @@
   "a.html.gz": 380,
   "a.js": 9961,
   "a.js.gz": 4350,
-  "a.wasm": 7820,
-  "a.wasm.gz": 3526,
-  "total": 18333,
-  "total_gz": 8256
+  "a.wasm": 7715,
+  "a.wasm.gz": 3508,
+  "total": 18228,
+  "total_gz": 8238
 }

test/code_size/embind_val_wasm.json

@@ -3,8 +3,8 @@
   "a.html.gz": 380,
   "a.js": 6849,
   "a.js.gz": 2947,
-  "a.wasm": 11586,
-  "a.wasm.gz": 5782,
-  "total": 18987,
-  "total_gz": 9109
+  "a.wasm": 9563,
+  "a.wasm.gz": 4917,
+  "total": 16964,
+  "total_gz": 8244
 }

test/common.py

@@ -577,8 +577,8 @@ def metafunc(self, mode, *args, **kwargs):
     else:
       self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
       self.set_setting('SUPPORT_LONGJMP', 'emscripten')
-      # DISABLE_EXCEPTION_CATCHING=0 exports __cxa_can_catch and
-      # __cxa_is_pointer_type, so if we don't build in C++ mode, wasm-ld will
+      # DISABLE_EXCEPTION_CATCHING=0 exports __cxa_can_catch,
+      # so if we don't build in C++ mode, wasm-ld will
       # error out because libc++abi is not included. See
       # https://github.com/emscripten-core/emscripten/pull/14192 for details.
       self.set_setting('DEFAULT_TO_CXX')

test/other/metadce/test_metadce_cxx_ctors1.exports

@@ -1,4 +1,3 @@
-__cxa_is_pointer_type
 __indirect_function_table
 __wasm_call_ctors
 _emscripten_stack_alloc

test/other/metadce/test_metadce_cxx_ctors1.size

@@ -1 +1 @@
-129474
+129316

test/other/metadce/test_metadce_cxx_ctors2.exports

@@ -1,4 +1,3 @@
-__cxa_is_pointer_type
 __indirect_function_table
 _emscripten_stack_alloc
 _emscripten_stack_restore