From 3cf21a0340ccd7fbcd7b950bce81bb7f5ba39259 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Fri, 18 Feb 2022 17:15:47 -0500
Subject: [PATCH 01/30] Wrote format_exception function and hard coded
 inclusion into system_libs

---
 system/lib/format_exception.cpp | 45 +++++++++++++++++++++++++++++++++
 tools/system_libs.py            | 10 +++++++-
 2 files changed, 54 insertions(+), 1 deletion(-)
 create mode 100644 system/lib/format_exception.cpp

diff --git a/system/lib/format_exception.cpp b/system/lib/format_exception.cpp
new file mode 100644
index 000000000000..bc02d71dcadd
--- /dev/null
+++ b/system/lib/format_exception.cpp
@@ -0,0 +1,45 @@
+#define __USING_EMSCRIPTEN_EXCEPTIONS__
+#include "cxa_exception.h"
+#include "cxxabi.h"
+#include <stdio.h>
+#include <typeinfo>
+
+extern "C" {
+
+#define DEMANGLED_BUF_SIZE 100
+
+int __cxa_can_catch(const std::type_info* catchType,
+                    const std::type_info* excpType,
+                    void** thrown);
+
+int format_exception(char** result, void* exc_ptr) {
+  __cxxabiv1::__cxa_exception* exc_info =
+    (__cxxabiv1::__cxa_exception*)exc_ptr - 1;
+  std::type_info* exc_type = exc_info->exceptionType;
+  const char* exc_name = exc_type->name();
+
+  int status = 0;
+  char* demangled_buf = __cxxabiv1::__cxa_demangle(exc_name, 0, 0, &status);
+  if (status == 0 && demangled_buf) {
+    exc_name = demangled_buf;
+  }
+
+  int can_catch = __cxa_can_catch(&typeid(std::exception), exc_type, &exc_ptr);
+  int ret;
+  if (can_catch) {
+    const char* exc_what = ((std::exception*)exc_ptr)->what();
+    ret = asprintf(result, "Cpp Exception %s: %s", exc_name, exc_what);
+  } else {
+    ret = asprintf(result,
+                   "Cpp Exception: The exception is an object of type '%s' at "
+                   "address %p which does not inherit from std::exception",
+                   exc_name,
+                   exc_ptr);
+  }
+
+  if (demangled_buf) {
+    free(demangled_buf);
+  }
+  return ret;
+}
+}
\ No newline at end of file
diff --git a/tools/system_libs.py b/tools/system_libs.py
index ceef98bad779..b51f5e525260 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -615,7 +615,7 @@ def __init__(self, **kwargs):
   def get_cflags(self):
     cflags = super().get_cflags()
     if self.is_wasm:
-      # DISABLE_EXCEPTION_THROWING=0 is the default, which is for Emscripten
+      # DISABLE_EXCEPTIOExceptionsN_THROWING=0 is the default, which is for Emscripten
       # EH/SjLj, so we should reverse it.
       cflags += ['-sSUPPORT_LONGJMP=wasm',
                  '-sDISABLE_EXCEPTION_THROWING=1',
@@ -1087,6 +1087,13 @@ def can_use(self):
     return super().can_use() and settings.USE_PTHREADS
 
 
+class libformatexception(Library):
+  name = 'libformatexception'
+  cflags = ['-Os']
+  src_dir = 'system/lib'
+  src_files = ['format_exception.cpp']
+  includes = ["system/lib/libcxxabi/src"]
+
 class libcxxabi(NoExceptLibrary, MTLibrary):
   name = 'libc++abi'
   cflags = [
@@ -1718,6 +1725,7 @@ def add_library(libname):
     need_whole_archive = lib.name in force_include and lib.get_ext() == '.a'
     libs_to_link.append((lib.get_link_flag(), need_whole_archive))
 
+  add_library('libformatexception')
   if '-nostartfiles' not in args:
     if settings.USE_PTHREADS:
       add_library('crtbegin')

From 2ea06c83b1a0dda760ed4921f4b82ecd99d6b1cd Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Fri, 18 Feb 2022 19:55:52 -0500
Subject: [PATCH 02/30] Add Javascript wrapper, miscellaneous cleanup

---
 src/library_exceptions.js       | 11 +++++++++++
 src/settings.js                 |  7 +++++++
 system/lib/format_exception.cpp |  2 --
 tools/system_libs.py            |  7 ++++---
 4 files changed, 22 insertions(+), 5 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 97942e5c6863..e436bb059997 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -428,6 +428,17 @@ var LibraryExceptions = {
     catchInfo.free();
     {{{ makeThrow('ptr') }}}
   },
+
+  $formatException__deps: ["format_exception"],
+  $formatException: function(excPtr){
+    var stackTop = stackSave();
+    var result_ptr = stackAlloc(4);
+    {{{ exportedAsmFunc('_format_exception') }}}(result_ptr, excPtr);
+    var result = UTF8ToString({{{ makeGetValue('result_ptr', '0', '*') }}});
+    stackRestore(stackTop);
+    _free(result_ptr);
+    return result;
+  }
 };
 
 // In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.
diff --git a/src/settings.js b/src/settings.js
index 80354a27b8c8..b08b0cdcc76b 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -339,6 +339,13 @@ var EXCEPTION_DEBUG = 0;
 // [link]
 var DEMANGLE_SUPPORT = 0;
 
+// If 1, expose a formatException function that can be used to format a top
+// level C++ exception. If the thrown exception was
+// throw new std::runtime_error("a big problem occurred")
+// It returns a string like: "Cpp Exception std::runtime_error: A big problem occured."
+// [link]
+var FORMAT_EXCEPTION_SUPPORT = 0;
+
 // Print out when we enter a library call (library*.js). You can also unset
 // Runtime.debug at runtime for logging to cease, and can set it when you want
 // it back. A simple way to set it in C++ is
diff --git a/system/lib/format_exception.cpp b/system/lib/format_exception.cpp
index bc02d71dcadd..295afcf4e428 100644
--- a/system/lib/format_exception.cpp
+++ b/system/lib/format_exception.cpp
@@ -1,11 +1,9 @@
-#define __USING_EMSCRIPTEN_EXCEPTIONS__
 #include "cxa_exception.h"
 #include "cxxabi.h"
 #include <stdio.h>
 #include <typeinfo>
 
 extern "C" {
-
 #define DEMANGLED_BUF_SIZE 100
 
 int __cxa_can_catch(const std::type_info* catchType,
diff --git a/tools/system_libs.py b/tools/system_libs.py
index b51f5e525260..b829c18e51fb 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1089,10 +1089,10 @@ def can_use(self):
 
 class libformatexception(Library):
   name = 'libformatexception'
-  cflags = ['-Os']
   src_dir = 'system/lib'
   src_files = ['format_exception.cpp']
-  includes = ["system/lib/libcxxabi/src"]
+  includes = ['system/lib/libcxxabi/src']
+  cflags = ['-Os', '-D__USING_EMSCRIPTEN_EXCEPTIONS__']
 
 class libcxxabi(NoExceptLibrary, MTLibrary):
   name = 'libc++abi'
@@ -1725,7 +1725,6 @@ def add_library(libname):
     need_whole_archive = lib.name in force_include and lib.get_ext() == '.a'
     libs_to_link.append((lib.get_link_flag(), need_whole_archive))
 
-  add_library('libformatexception')
   if '-nostartfiles' not in args:
     if settings.USE_PTHREADS:
       add_library('crtbegin')
@@ -1784,6 +1783,8 @@ def add_library(libname):
     add_library('libc++abi')
     if settings.EXCEPTION_HANDLING:
       add_library('libunwind')
+  if settings.FORMAT_EXCEPTION_SUPPORT:
+    add_library("libformatexception")
 
   if settings.USE_ASAN:
     force_include.append('libasan_rt')

From 693f677ca28622af94c398f1193505bf735741b0 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Fri, 18 Feb 2022 20:05:46 -0500
Subject: [PATCH 03/30] Fix formatting

---
 tools/system_libs.py | 1 +
 1 file changed, 1 insertion(+)

diff --git a/tools/system_libs.py b/tools/system_libs.py
index b829c18e51fb..491b2282fb09 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1094,6 +1094,7 @@ class libformatexception(Library):
   includes = ['system/lib/libcxxabi/src']
   cflags = ['-Os', '-D__USING_EMSCRIPTEN_EXCEPTIONS__']
 
+
 class libcxxabi(NoExceptLibrary, MTLibrary):
   name = 'libc++abi'
   cflags = [

From 95ef456736d61bc1a2c15cdd317d0d7f3c130564 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 10:20:33 -0500
Subject: [PATCH 04/30] No need for exportedAsmFunction

---
 src/library_exceptions.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index e436bb059997..e29b2327d593 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -433,7 +433,7 @@ var LibraryExceptions = {
   $formatException: function(excPtr){
     var stackTop = stackSave();
     var result_ptr = stackAlloc(4);
-    {{{ exportedAsmFunc('_format_exception') }}}(result_ptr, excPtr);
+    _format_exception(result_ptr, excPtr);
     var result = UTF8ToString({{{ makeGetValue('result_ptr', '0', '*') }}});
     stackRestore(stackTop);
     _free(result_ptr);

From 103dca8d6d9042e00e0dba7e315df406f0d167d0 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:45:17 -0500
Subject: [PATCH 05/30] Use withStackSave

---
 src/library_exceptions.js | 8 +++-----
 1 file changed, 3 insertions(+), 5 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index e29b2327d593..0a34ca020080 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -429,16 +429,14 @@ var LibraryExceptions = {
     {{{ makeThrow('ptr') }}}
   },
 
-  $formatException__deps: ["format_exception"],
-  $formatException: function(excPtr){
-    var stackTop = stackSave();
+  $formatException__deps: ["format_exception", "$withStackSave"],
+  $formatException: withStackSave(function(excPtr){
     var result_ptr = stackAlloc(4);
     _format_exception(result_ptr, excPtr);
     var result = UTF8ToString({{{ makeGetValue('result_ptr', '0', '*') }}});
-    stackRestore(stackTop);
     _free(result_ptr);
     return result;
-  }
+  }),
 };
 
 // In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.

From cc31016e5a99e7e83e2c515da1aaa731940fdc7d Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:45:55 -0500
Subject: [PATCH 06/30] Free the right thing

---
 src/library_exceptions.js | 5 +++--
 1 file changed, 3 insertions(+), 2 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 0a34ca020080..8ed504363853 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -433,8 +433,9 @@ var LibraryExceptions = {
   $formatException: withStackSave(function(excPtr){
     var result_ptr = stackAlloc(4);
     _format_exception(result_ptr, excPtr);
-    var result = UTF8ToString({{{ makeGetValue('result_ptr', '0', '*') }}});
-    _free(result_ptr);
+    var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
+    var result = UTF8ToString(utf8_addr);
+    _free(utf_addr);
     return result;
   }),
 };

From 5ca4f183ff46ce518a88892ac6d3873ac7803aff Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:46:34 -0500
Subject: [PATCH 07/30] Use stackAlloc({{{ POINTER_SIZE }}});

---
 src/library_exceptions.js | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 8ed504363853..8825d6c4cbc0 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -431,7 +431,7 @@ var LibraryExceptions = {
 
   $formatException__deps: ["format_exception", "$withStackSave"],
   $formatException: withStackSave(function(excPtr){
-    var result_ptr = stackAlloc(4);
+    var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
     _format_exception(result_ptr, excPtr);
     var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
     var result = UTF8ToString(utf8_addr);

From aa15cc8a6ad14cb4e048bd38a36658418a71eb86 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:48:39 -0500
Subject: [PATCH 08/30] Remove accidental change

---
 tools/system_libs.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tools/system_libs.py b/tools/system_libs.py
index 491b2282fb09..1b482819f3ac 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -615,7 +615,7 @@ def __init__(self, **kwargs):
   def get_cflags(self):
     cflags = super().get_cflags()
     if self.is_wasm:
-      # DISABLE_EXCEPTIOExceptionsN_THROWING=0 is the default, which is for Emscripten
+      # DISABLE_EXCEPTION_THROWING=0 is the default, which is for Emscripten
       # EH/SjLj, so we should reverse it.
       cflags += ['-sSUPPORT_LONGJMP=wasm',
                  '-sDISABLE_EXCEPTION_THROWING=1',

From 493e22f0b3728651979f1b0582a29f8ba5318681 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:49:35 -0500
Subject: [PATCH 09/30] Add final newline to format_exception.cpp

---
 system/lib/format_exception.cpp | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/system/lib/format_exception.cpp b/system/lib/format_exception.cpp
index 295afcf4e428..45a479689b58 100644
--- a/system/lib/format_exception.cpp
+++ b/system/lib/format_exception.cpp
@@ -40,4 +40,4 @@ int format_exception(char** result, void* exc_ptr) {
   }
   return ret;
 }
-}
\ No newline at end of file
+}

From c7d126729ff5fa1a21d3e0f2b666a756cea63817 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:50:11 -0500
Subject: [PATCH 10/30] Add emscripten_ prefix to format_exception

---
 src/library_exceptions.js       | 2 +-
 system/lib/format_exception.cpp | 2 +-
 2 files changed, 2 insertions(+), 2 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 8825d6c4cbc0..bdf8625a14e3 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -432,7 +432,7 @@ var LibraryExceptions = {
   $formatException__deps: ["format_exception", "$withStackSave"],
   $formatException: withStackSave(function(excPtr){
     var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
-    _format_exception(result_ptr, excPtr);
+    _emscripten_format_exception(result_ptr, excPtr);
     var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
     var result = UTF8ToString(utf8_addr);
     _free(utf_addr);
diff --git a/system/lib/format_exception.cpp b/system/lib/format_exception.cpp
index 45a479689b58..abdce817a4b2 100644
--- a/system/lib/format_exception.cpp
+++ b/system/lib/format_exception.cpp
@@ -10,7 +10,7 @@ int __cxa_can_catch(const std::type_info* catchType,
                     const std::type_info* excpType,
                     void** thrown);
 
-int format_exception(char** result, void* exc_ptr) {
+int emscripten_format_exception(char** result, void* exc_ptr) {
   __cxxabiv1::__cxa_exception* exc_info =
     (__cxxabiv1::__cxa_exception*)exc_ptr - 1;
   std::type_info* exc_type = exc_info->exceptionType;

From 0231037c70735d1916428d4890db6b142186a00f Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 16:57:10 -0500
Subject: [PATCH 11/30] Add format_exception.cpp to libcxxabi

---
 system/lib/{ => libcxxabi}/format_exception.cpp | 0
 tools/system_libs.py                            | 3 +++
 2 files changed, 3 insertions(+)
 rename system/lib/{ => libcxxabi}/format_exception.cpp (100%)

diff --git a/system/lib/format_exception.cpp b/system/lib/libcxxabi/format_exception.cpp
similarity index 100%
rename from system/lib/format_exception.cpp
rename to system/lib/libcxxabi/format_exception.cpp
diff --git a/tools/system_libs.py b/tools/system_libs.py
index 1b482819f3ac..2ef6e8636be2 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1146,6 +1146,9 @@ def get_files(self):
         'cxa_personality.cpp'
       ]
 
+    if settings.FORMAT_EXCEPTION_SUPPORT:
+      filenames += ["format_exception.cpp"]
+
     return files_in_path(
         path='system/lib/libcxxabi/src',
         filenames=filenames)

From af456b1e9a626dbbf7d1f77bae637041e92d09e4 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 17:09:00 -0500
Subject: [PATCH 12/30] Use withStackSave correctly

---
 src/library_exceptions.js | 18 ++++++++++--------
 1 file changed, 10 insertions(+), 8 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index bdf8625a14e3..061d1cda3f63 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -430,14 +430,16 @@ var LibraryExceptions = {
   },
 
   $formatException__deps: ["format_exception", "$withStackSave"],
-  $formatException: withStackSave(function(excPtr){
-    var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
-    _emscripten_format_exception(result_ptr, excPtr);
-    var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
-    var result = UTF8ToString(utf8_addr);
-    _free(utf_addr);
-    return result;
-  }),
+  $formatException: function(excPtr){
+      return withStackSave(function(){
+      var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
+      _emscripten_format_exception(result_ptr, excPtr);
+      var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
+      var result = UTF8ToString(utf8_addr);
+      _free(utf_addr);
+      return result;
+    });
+  },
 };
 
 // In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.

From e233943d7f6ebd8da5ab95b9b8a9ff9fb698447e Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 17:10:10 -0500
Subject: [PATCH 13/30] Remove libformatexception library

---
 tools/system_libs.py | 10 ----------
 1 file changed, 10 deletions(-)

diff --git a/tools/system_libs.py b/tools/system_libs.py
index 2ef6e8636be2..18892103b942 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1087,14 +1087,6 @@ def can_use(self):
     return super().can_use() and settings.USE_PTHREADS
 
 
-class libformatexception(Library):
-  name = 'libformatexception'
-  src_dir = 'system/lib'
-  src_files = ['format_exception.cpp']
-  includes = ['system/lib/libcxxabi/src']
-  cflags = ['-Os', '-D__USING_EMSCRIPTEN_EXCEPTIONS__']
-
-
 class libcxxabi(NoExceptLibrary, MTLibrary):
   name = 'libc++abi'
   cflags = [
@@ -1787,8 +1779,6 @@ def add_library(libname):
     add_library('libc++abi')
     if settings.EXCEPTION_HANDLING:
       add_library('libunwind')
-  if settings.FORMAT_EXCEPTION_SUPPORT:
-    add_library("libformatexception")
 
   if settings.USE_ASAN:
     force_include.append('libasan_rt')

From 83a1a4aef43b81ae63504c6901e07d13abceded3 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 17:28:25 -0500
Subject: [PATCH 14/30] Various fixes

---
 emcc.py                                             | 4 ++++
 src/library_exceptions.js                           | 4 ++--
 system/lib/libcxxabi/{ => src}/format_exception.cpp | 0
 tools/system_libs.py                                | 6 ++----
 4 files changed, 8 insertions(+), 6 deletions(-)
 rename system/lib/libcxxabi/{ => src}/format_exception.cpp (100%)

diff --git a/emcc.py b/emcc.py
index c243d53d0492..772edeb2b1a2 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2074,6 +2074,10 @@ def default_setting(name, new_default):
   else:
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
+  if settings.FORMAT_EXCEPTION_SUPPORT:
+    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
+    settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception"]
+
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage
     # may need, including filesystem usage from standalone file packager output (i.e.
diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 061d1cda3f63..a6ffde78c597 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -429,14 +429,14 @@ var LibraryExceptions = {
     {{{ makeThrow('ptr') }}}
   },
 
-  $formatException__deps: ["format_exception", "$withStackSave"],
+  $formatException__deps: ["emscripten_format_exception", "$withStackSave"],
   $formatException: function(excPtr){
       return withStackSave(function(){
       var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
       _emscripten_format_exception(result_ptr, excPtr);
       var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
       var result = UTF8ToString(utf8_addr);
-      _free(utf_addr);
+      _free(utf8_addr);
       return result;
     });
   },
diff --git a/system/lib/libcxxabi/format_exception.cpp b/system/lib/libcxxabi/src/format_exception.cpp
similarity index 100%
rename from system/lib/libcxxabi/format_exception.cpp
rename to system/lib/libcxxabi/src/format_exception.cpp
diff --git a/tools/system_libs.py b/tools/system_libs.py
index 18892103b942..0c0dfefd2697 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1127,7 +1127,8 @@ def get_files(self):
       'stdlib_exception.cpp',
       'stdlib_stdexcept.cpp',
       'stdlib_typeinfo.cpp',
-      'private_typeinfo.cpp'
+      'private_typeinfo.cpp',
+      'format_exception.cpp'
     ]
     if self.eh_mode == Exceptions.NONE:
       filenames += ['cxa_noexception.cpp']
@@ -1138,9 +1139,6 @@ def get_files(self):
         'cxa_personality.cpp'
       ]
 
-    if settings.FORMAT_EXCEPTION_SUPPORT:
-      filenames += ["format_exception.cpp"]
-
     return files_in_path(
         path='system/lib/libcxxabi/src',
         filenames=filenames)

From 5e765ab142836abff308a1c5bf6db51cb31a41e3 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 18:00:03 -0500
Subject: [PATCH 15/30] Add test

---
 emcc.py                   |  3 +-
 src/library_exceptions.js |  2 +-
 tests/test_core.py        | 59 +++++++++++++++++++++++++++++++++++++++
 3 files changed, 62 insertions(+), 2 deletions(-)

diff --git a/emcc.py b/emcc.py
index 772edeb2b1a2..1162bf3f1489 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2076,7 +2076,8 @@ def default_setting(name, new_default):
 
   if settings.FORMAT_EXCEPTION_SUPPORT:
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
-    settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception"]
+    settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception", "_free"]
+    settings.EXPORTED_RUNTIME_METHODS += ["formatException"]
 
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage
diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index a6ffde78c597..0f071771e2db 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -429,7 +429,7 @@ var LibraryExceptions = {
     {{{ makeThrow('ptr') }}}
   },
 
-  $formatException__deps: ["emscripten_format_exception", "$withStackSave"],
+  $formatException__deps: ["emscripten_format_exception", "$withStackSave", "free"],
   $formatException: function(excPtr){
       return withStackSave(function(){
       var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
diff --git a/tests/test_core.py b/tests/test_core.py
index 7dfac2dc7102..33f2a860584c 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1543,6 +1543,65 @@ def test_exceptions_rethrow_missing(self):
     create_file('main.cpp', 'int main() { throw; }')
     self.do_runf('main.cpp', None, assert_returncode=NON_ZERO)
 
+  @with_both_eh_sjlj
+  def test_format_exception(self):
+    # needs to flush stdio streams
+    self.set_setting('EXIT_RUNTIME')
+    self.set_setting('EXPORTED_FUNCTIONS', ['_main', '_throw_exc'])
+    self.set_setting('FORMAT_EXCEPTION_SUPPORT')
+    self.maybe_closure()
+    self.do_run(
+      """
+      #include <emscripten.h>
+      #include <exception>
+      #include <stdexcept>
+      using namespace std;
+
+      class myexception : public exception
+      {
+        virtual const char* what() const throw() { return "My exception happened"; }
+      } myex;
+
+      extern "C" void
+      throw_exc(int x)
+      {
+        if (x == 1) {
+          throw 1000;
+        }
+        if (x == 2) {
+          throw 'c';
+        }
+        if (x == 3) {
+          throw runtime_error("abc");
+        }
+        if (x == 4) {
+          throw myex;
+        }
+        if (x == 5) {
+          throw "abc";
+        }
+      }
+
+      int
+      main(){
+          EM_ASM({
+            for(let i = 1; i < 6; i++){
+              try {
+                  Module["_throw_exc"](i);
+              } catch(p){
+                  console.log(Module["formatException"](p));
+              }
+            }
+          });
+      }
+      """,
+      "Cpp Exception: The exception is an object of type 'int' at address 0x503868 which does not inherit from std::exception\n"
+      "Cpp Exception: The exception is an object of type 'char' at address 0x503880 which does not inherit from std::exception\n"
+      "Cpp Exception std::runtime_error: abc\n"
+      "Cpp Exception myexception: My exception happened\n"
+      "Cpp Exception: The exception is an object of type 'char const*' at address 0x5038e8 which does not inherit from std::exception\n"
+    )
+
   @with_both_eh_sjlj
   def test_bad_typeid(self):
     self.do_run(r'''

From 123560005c5da30b06934535bc5d8820c345fd49 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 18:06:57 -0500
Subject: [PATCH 16/30] Remove addresses from test comparison

---
 tests/test_core.py | 8 ++++----
 1 file changed, 4 insertions(+), 4 deletions(-)

diff --git a/tests/test_core.py b/tests/test_core.py
index 33f2a860584c..6d0a26b63b9e 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1589,17 +1589,17 @@ class myexception : public exception
               try {
                   Module["_throw_exc"](i);
               } catch(p){
-                  console.log(Module["formatException"](p));
+                  console.log(Module["formatException"](p).replace(/0x[0-9a-f]*/, "xxx"));
               }
             }
           });
       }
       """,
-      "Cpp Exception: The exception is an object of type 'int' at address 0x503868 which does not inherit from std::exception\n"
-      "Cpp Exception: The exception is an object of type 'char' at address 0x503880 which does not inherit from std::exception\n"
+      "Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception\n"
+      "Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception\n"
       "Cpp Exception std::runtime_error: abc\n"
       "Cpp Exception myexception: My exception happened\n"
-      "Cpp Exception: The exception is an object of type 'char const*' at address 0x5038e8 which does not inherit from std::exception\n"
+      "Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception\n"
     )
 
   @with_both_eh_sjlj

From a83007e375133243f989f64c874d3fef73636400 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 19:09:36 -0500
Subject: [PATCH 17/30] Try to fix test

---
 tests/test_core.py | 2 +-
 1 file changed, 1 insertion(+), 1 deletion(-)

diff --git a/tests/test_core.py b/tests/test_core.py
index 6d0a26b63b9e..c3f5e4a66c81 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1543,12 +1543,12 @@ def test_exceptions_rethrow_missing(self):
     create_file('main.cpp', 'int main() { throw; }')
     self.do_runf('main.cpp', None, assert_returncode=NON_ZERO)
 
-  @with_both_eh_sjlj
   def test_format_exception(self):
     # needs to flush stdio streams
     self.set_setting('EXIT_RUNTIME')
     self.set_setting('EXPORTED_FUNCTIONS', ['_main', '_throw_exc'])
     self.set_setting('FORMAT_EXCEPTION_SUPPORT')
+    self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.maybe_closure()
     self.do_run(
       """

From 5f19ef5c80abd0b6a115799415ea82a33c697d67 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 19:54:19 -0500
Subject: [PATCH 18/30] Fix wasm-exceptions test

---
 system/lib/libcxxabi/src/format_exception.cpp | 4 ++++
 1 file changed, 4 insertions(+)

diff --git a/system/lib/libcxxabi/src/format_exception.cpp b/system/lib/libcxxabi/src/format_exception.cpp
index abdce817a4b2..b1babd43350c 100644
--- a/system/lib/libcxxabi/src/format_exception.cpp
+++ b/system/lib/libcxxabi/src/format_exception.cpp
@@ -3,6 +3,8 @@
 #include <stdio.h>
 #include <typeinfo>
 
+#ifdef __USING_EMSCRIPTEN_EXCEPTIONS__
+
 extern "C" {
 #define DEMANGLED_BUF_SIZE 100
 
@@ -41,3 +43,5 @@ int emscripten_format_exception(char** result, void* exc_ptr) {
   return ret;
 }
 }
+
+#endif // __USING_EMSCRIPTEN_EXCEPTIONS__

From 86b703b67b92e1db2fde3d4f256aff864fc6d81c Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Sun, 20 Feb 2022 22:02:28 -0500
Subject: [PATCH 19/30] Fix test

---
 src/library_exceptions.js | 2 ++
 1 file changed, 2 insertions(+)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 0f071771e2db..eec90ff0f0bc 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -429,6 +429,7 @@ var LibraryExceptions = {
     {{{ makeThrow('ptr') }}}
   },
 
+#if !DISABLE_EXCEPTION_CATCHING
   $formatException__deps: ["emscripten_format_exception", "$withStackSave", "free"],
   $formatException: function(excPtr){
       return withStackSave(function(){
@@ -440,6 +441,7 @@ var LibraryExceptions = {
       return result;
     });
   },
+#endif
 };
 
 // In LLVM, exceptions generate a set of functions of form __cxa_find_matching_catch_1(), __cxa_find_matching_catch_2(), etc.

From a773e9bd31525b991365c8a5c875da86026652ca Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 09:34:07 -0500
Subject: [PATCH 20/30] Fix INCLUDE_FULL_LIBRARY test

---
 emcc.py | 8 ++++++--
 1 file changed, 6 insertions(+), 2 deletions(-)

diff --git a/emcc.py b/emcc.py
index 1162bf3f1489..ea114a5bf870 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2074,8 +2074,12 @@ def default_setting(name, new_default):
   else:
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
-  if settings.FORMAT_EXCEPTION_SUPPORT:
-    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
+  if (
+      settings.FORMAT_EXCEPTION_SUPPORT
+      or "$formatException" in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE
+      or settings.INCLUDE_FULL_LIBRARY
+  ):
+    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ["$formatException"]
     settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception", "_free"]
     settings.EXPORTED_RUNTIME_METHODS += ["formatException"]
 

From 16f160d38264fe1c160eb2ffa7c4d1bfb5a7a5ad Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 09:39:40 -0500
Subject: [PATCH 21/30] Fix flake8

---
 emcc.py | 6 +++---
 1 file changed, 3 insertions(+), 3 deletions(-)

diff --git a/emcc.py b/emcc.py
index ea114a5bf870..7d6655590374 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2075,9 +2075,9 @@ def default_setting(name, new_default):
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
   if (
-      settings.FORMAT_EXCEPTION_SUPPORT
-      or "$formatException" in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE
-      or settings.INCLUDE_FULL_LIBRARY
+      settings.FORMAT_EXCEPTION_SUPPORT or
+      "$formatException" in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE or
+      settings.INCLUDE_FULL_LIBRARY
   ):
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ["$formatException"]
     settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception", "_free"]

From fbcf6da21d9349e40fc920ec3b90948475d4b3f0 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 21:47:37 -0500
Subject: [PATCH 22/30] Formatting fixes from sbc100

---
 src/library_exceptions.js                     |  4 +--
 system/lib/libcxxabi/src/format_exception.cpp |  1 -
 tests/test_core.py                            | 31 ++++++++-----------
 tools/system_libs.py                          |  2 +-
 4 files changed, 16 insertions(+), 22 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index eec90ff0f0bc..3ed38377ebd4 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -431,8 +431,8 @@ var LibraryExceptions = {
 
 #if !DISABLE_EXCEPTION_CATCHING
   $formatException__deps: ["emscripten_format_exception", "$withStackSave", "free"],
-  $formatException: function(excPtr){
-      return withStackSave(function(){
+  $formatException: function(excPtr) {
+    return withStackSave(function(){
       var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
       _emscripten_format_exception(result_ptr, excPtr);
       var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
diff --git a/system/lib/libcxxabi/src/format_exception.cpp b/system/lib/libcxxabi/src/format_exception.cpp
index b1babd43350c..5972ff7a6881 100644
--- a/system/lib/libcxxabi/src/format_exception.cpp
+++ b/system/lib/libcxxabi/src/format_exception.cpp
@@ -6,7 +6,6 @@
 #ifdef __USING_EMSCRIPTEN_EXCEPTIONS__
 
 extern "C" {
-#define DEMANGLED_BUF_SIZE 100
 
 int __cxa_can_catch(const std::type_info* catchType,
                     const std::type_info* excpType,
diff --git a/tests/test_core.py b/tests/test_core.py
index c3f5e4a66c81..6abb3de1be2e 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1550,21 +1550,17 @@ def test_format_exception(self):
     self.set_setting('FORMAT_EXCEPTION_SUPPORT')
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.maybe_closure()
-    self.do_run(
-      """
+    self.do_run('''
       #include <emscripten.h>
       #include <exception>
       #include <stdexcept>
       using namespace std;
 
-      class myexception : public exception
-      {
+      class myexception : public exception {
         virtual const char* what() const throw() { return "My exception happened"; }
       } myex;
 
-      extern "C" void
-      throw_exc(int x)
-      {
+      extern "C" void throw_exc(int x) {
         if (x == 1) {
           throw 1000;
         }
@@ -1582,25 +1578,24 @@ class myexception : public exception
         }
       }
 
-      int
-      main(){
+      int main() {
           EM_ASM({
-            for(let i = 1; i < 6; i++){
+            for (let i = 1; i < 6; i++){
               try {
                   Module["_throw_exc"](i);
-              } catch(p){
+              } catch(p) {
                   console.log(Module["formatException"](p).replace(/0x[0-9a-f]*/, "xxx"));
               }
             }
           });
       }
-      """,
-      "Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception\n"
-      "Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception\n"
-      "Cpp Exception std::runtime_error: abc\n"
-      "Cpp Exception myexception: My exception happened\n"
-      "Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception\n"
-    )
+      ''', '''
+      Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception
+      Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception
+      Cpp Exception std::runtime_error: abc
+      Cpp Exception myexception: My exception happened
+      Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception
+    ''')
 
   @with_both_eh_sjlj
   def test_bad_typeid(self):
diff --git a/tools/system_libs.py b/tools/system_libs.py
index 0c0dfefd2697..31035e5fa850 100644
--- a/tools/system_libs.py
+++ b/tools/system_libs.py
@@ -1128,7 +1128,7 @@ def get_files(self):
       'stdlib_stdexcept.cpp',
       'stdlib_typeinfo.cpp',
       'private_typeinfo.cpp',
-      'format_exception.cpp'
+      'format_exception.cpp',
     ]
     if self.eh_mode == Exceptions.NONE:
       filenames += ['cxa_noexception.cpp']

From 8ad79321cb258a12270a89f8f6649f8812cd88cd Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 21:52:09 -0500
Subject: [PATCH 23/30] Fix test

---
 tests/test_core.py | 19 +++++++++++--------
 1 file changed, 11 insertions(+), 8 deletions(-)

diff --git a/tests/test_core.py b/tests/test_core.py
index 6abb3de1be2e..496fde36cf52 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1550,7 +1550,7 @@ def test_format_exception(self):
     self.set_setting('FORMAT_EXCEPTION_SUPPORT')
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.maybe_closure()
-    self.do_run('''
+    src = '''
       #include <emscripten.h>
       #include <exception>
       #include <stdexcept>
@@ -1589,13 +1589,16 @@ class myexception : public exception {
             }
           });
       }
-      ''', '''
-      Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception
-      Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception
-      Cpp Exception std::runtime_error: abc
-      Cpp Exception myexception: My exception happened
-      Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception
-    ''')
+    '''
+    expected = '''
+Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception
+Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception
+Cpp Exception std::runtime_error: abc
+Cpp Exception myexception: My exception happened
+Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception
+    '''.strip() + "\n"
+
+    self.do_run(src, expected)
 
   @with_both_eh_sjlj
   def test_bad_typeid(self):

From 68c129e568b3c1c8b6cde49abb9b6bf06a55e913 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 21:58:03 -0500
Subject: [PATCH 24/30] Return char* instead of returning by value to avoid
 stackAlloc

---
 src/library_exceptions.js                     | 12 ++++--------
 system/lib/libcxxabi/src/format_exception.cpp | 18 +++++++++---------
 2 files changed, 13 insertions(+), 17 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index 3ed38377ebd4..d840be63cc71 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -432,14 +432,10 @@ var LibraryExceptions = {
 #if !DISABLE_EXCEPTION_CATCHING
   $formatException__deps: ["emscripten_format_exception", "$withStackSave", "free"],
   $formatException: function(excPtr) {
-    return withStackSave(function(){
-      var result_ptr = stackAlloc({{{ POINTER_SIZE }}});
-      _emscripten_format_exception(result_ptr, excPtr);
-      var utf8_addr = {{{ makeGetValue('result_ptr', '0', '*') }}};
-      var result = UTF8ToString(utf8_addr);
-      _free(utf8_addr);
-      return result;
-    });
+    var utf8_addr = _emscripten_format_exception(excPtr);
+    var result = UTF8ToString(utf8_addr);
+    _free(utf8_addr);
+    return result;
   },
 #endif
 };
diff --git a/system/lib/libcxxabi/src/format_exception.cpp b/system/lib/libcxxabi/src/format_exception.cpp
index 5972ff7a6881..5d93d666ad82 100644
--- a/system/lib/libcxxabi/src/format_exception.cpp
+++ b/system/lib/libcxxabi/src/format_exception.cpp
@@ -11,7 +11,7 @@ int __cxa_can_catch(const std::type_info* catchType,
                     const std::type_info* excpType,
                     void** thrown);
 
-int emscripten_format_exception(char** result, void* exc_ptr) {
+char* emscripten_format_exception(void* exc_ptr) {
   __cxxabiv1::__cxa_exception* exc_info =
     (__cxxabiv1::__cxa_exception*)exc_ptr - 1;
   std::type_info* exc_type = exc_info->exceptionType;
@@ -24,22 +24,22 @@ int emscripten_format_exception(char** result, void* exc_ptr) {
   }
 
   int can_catch = __cxa_can_catch(&typeid(std::exception), exc_type, &exc_ptr);
-  int ret;
+  char* result = NULL;
   if (can_catch) {
     const char* exc_what = ((std::exception*)exc_ptr)->what();
-    ret = asprintf(result, "Cpp Exception %s: %s", exc_name, exc_what);
+    asprintf(&result, "Cpp Exception %s: %s", exc_name, exc_what);
   } else {
-    ret = asprintf(result,
-                   "Cpp Exception: The exception is an object of type '%s' at "
-                   "address %p which does not inherit from std::exception",
-                   exc_name,
-                   exc_ptr);
+    asprintf(&result,
+             "Cpp Exception: The exception is an object of type '%s' at "
+             "address %p which does not inherit from std::exception",
+             exc_name,
+             exc_ptr);
   }
 
   if (demangled_buf) {
     free(demangled_buf);
   }
-  return ret;
+  return result;
 }
 }
 

From c11d0361a1cd73dd89abbbbb2066255950e0477f Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 22:01:14 -0500
Subject: [PATCH 25/30] Remove FORMAT_EXCEPTION_SUPPORT setting

---
 emcc.py            | 9 ++++-----
 src/settings.js    | 7 -------
 tests/test_core.py | 2 +-
 3 files changed, 5 insertions(+), 13 deletions(-)

diff --git a/emcc.py b/emcc.py
index 7d6655590374..60a828be0ee6 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2075,13 +2075,12 @@ def default_setting(name, new_default):
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
   if (
-      settings.FORMAT_EXCEPTION_SUPPORT or
       "$formatException" in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE or
-      settings.INCLUDE_FULL_LIBRARY
+      settings.INCLUDE_FULL_LIBRARY and not settings.DISABLE_EXCEPTION_CATCHING
   ):
-    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ["$formatException"]
-    settings.EXPORTED_FUNCTIONS += ["_emscripten_format_exception", "_free"]
-    settings.EXPORTED_RUNTIME_METHODS += ["formatException"]
+    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
+    settings.EXPORTED_FUNCTIONS += ['_emscripten_format_exception', '_free']
+    settings.EXPORTED_RUNTIME_METHODS += ['formatException']
 
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage
diff --git a/src/settings.js b/src/settings.js
index b08b0cdcc76b..80354a27b8c8 100644
--- a/src/settings.js
+++ b/src/settings.js
@@ -339,13 +339,6 @@ var EXCEPTION_DEBUG = 0;
 // [link]
 var DEMANGLE_SUPPORT = 0;
 
-// If 1, expose a formatException function that can be used to format a top
-// level C++ exception. If the thrown exception was
-// throw new std::runtime_error("a big problem occurred")
-// It returns a string like: "Cpp Exception std::runtime_error: A big problem occured."
-// [link]
-var FORMAT_EXCEPTION_SUPPORT = 0;
-
 // Print out when we enter a library call (library*.js). You can also unset
 // Runtime.debug at runtime for logging to cease, and can set it when you want
 // it back. A simple way to set it in C++ is
diff --git a/tests/test_core.py b/tests/test_core.py
index 496fde36cf52..42ebdf51f9bb 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1547,8 +1547,8 @@ def test_format_exception(self):
     # needs to flush stdio streams
     self.set_setting('EXIT_RUNTIME')
     self.set_setting('EXPORTED_FUNCTIONS', ['_main', '_throw_exc'])
-    self.set_setting('FORMAT_EXCEPTION_SUPPORT')
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
+    self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$formatException'])
     self.maybe_closure()
     src = '''
       #include <emscripten.h>

From 9c0b0a6cb3c9e8d231eb5e752096e7ba8fb0b5d1 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 22:19:03 -0500
Subject: [PATCH 26/30] Address more review comments

---
 src/library_exceptions.js | 2 +-
 tests/test_core.py        | 4 ++--
 2 files changed, 3 insertions(+), 3 deletions(-)

diff --git a/src/library_exceptions.js b/src/library_exceptions.js
index d840be63cc71..a8a85b3737ff 100644
--- a/src/library_exceptions.js
+++ b/src/library_exceptions.js
@@ -430,7 +430,7 @@ var LibraryExceptions = {
   },
 
 #if !DISABLE_EXCEPTION_CATCHING
-  $formatException__deps: ["emscripten_format_exception", "$withStackSave", "free"],
+  $formatException__deps: ['emscripten_format_exception', 'free'],
   $formatException: function(excPtr) {
     var utf8_addr = _emscripten_format_exception(excPtr);
     var result = UTF8ToString(utf8_addr);
diff --git a/tests/test_core.py b/tests/test_core.py
index 42ebdf51f9bb..ddf54b1c6a38 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1590,13 +1590,13 @@ class myexception : public exception {
           });
       }
     '''
-    expected = '''
+    expected = '''\
 Cpp Exception: The exception is an object of type 'int' at address xxx which does not inherit from std::exception
 Cpp Exception: The exception is an object of type 'char' at address xxx which does not inherit from std::exception
 Cpp Exception std::runtime_error: abc
 Cpp Exception myexception: My exception happened
 Cpp Exception: The exception is an object of type 'char const*' at address xxx which does not inherit from std::exception
-    '''.strip() + "\n"
+'''
 
     self.do_run(src, expected)
 

From 439c09fcbaddbac95eb8c9189b30aeb0fc361b2a Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 22:21:08 -0500
Subject: [PATCH 27/30] Address more review comments

---
 emcc.py            | 2 +-
 tests/test_core.py | 3 +--
 2 files changed, 2 insertions(+), 3 deletions(-)

diff --git a/emcc.py b/emcc.py
index 60a828be0ee6..0b1566359e4f 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2075,7 +2075,7 @@ def default_setting(name, new_default):
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
   if (
-      "$formatException" in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE or
+      '$formatException' in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE or
       settings.INCLUDE_FULL_LIBRARY and not settings.DISABLE_EXCEPTION_CATCHING
   ):
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
diff --git a/tests/test_core.py b/tests/test_core.py
index ddf54b1c6a38..8a1e4b153843 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1546,7 +1546,6 @@ def test_exceptions_rethrow_missing(self):
   def test_format_exception(self):
     # needs to flush stdio streams
     self.set_setting('EXIT_RUNTIME')
-    self.set_setting('EXPORTED_FUNCTIONS', ['_main', '_throw_exc'])
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$formatException'])
     self.maybe_closure()
@@ -1560,7 +1559,7 @@ class myexception : public exception {
         virtual const char* what() const throw() { return "My exception happened"; }
       } myex;
 
-      extern "C" void throw_exc(int x) {
+      EMSCRIPTEN_KEEPALIVE extern "C" void throw_exc(int x) {
         if (x == 1) {
           throw 1000;
         }

From 77376ea606185d74e4cd190670ae8636e7a7c714 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 22:21:57 -0500
Subject: [PATCH 28/30] Remove unneeded setting

---
 tests/test_core.py | 2 --
 1 file changed, 2 deletions(-)

diff --git a/tests/test_core.py b/tests/test_core.py
index 8a1e4b153843..6c42691f6c41 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1544,8 +1544,6 @@ def test_exceptions_rethrow_missing(self):
     self.do_runf('main.cpp', None, assert_returncode=NON_ZERO)
 
   def test_format_exception(self):
-    # needs to flush stdio streams
-    self.set_setting('EXIT_RUNTIME')
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$formatException'])
     self.maybe_closure()

From 8dad972fb0107712df2c6b5fe2dcf674e4133d05 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Mon, 21 Feb 2022 22:25:51 -0500
Subject: [PATCH 29/30] Add formatException to EXPORTED_FUNCTIONS rather than
 EXPORTED_RUNTIME_METHODS

---
 emcc.py | 3 +--
 1 file changed, 1 insertion(+), 2 deletions(-)

diff --git a/emcc.py b/emcc.py
index 0b1566359e4f..4e15c949f80d 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2079,8 +2079,7 @@ def default_setting(name, new_default):
       settings.INCLUDE_FULL_LIBRARY and not settings.DISABLE_EXCEPTION_CATCHING
   ):
     settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
-    settings.EXPORTED_FUNCTIONS += ['_emscripten_format_exception', '_free']
-    settings.EXPORTED_RUNTIME_METHODS += ['formatException']
+    settings.EXPORTED_FUNCTIONS += ['formatException', '_emscripten_format_exception', '_free']
 
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage

From dcc15f55e7ba6f5d276d0955e810dd80ab96bfc1 Mon Sep 17 00:00:00 2001
From: Hood Chatham <roberthoodchatham@gmail.com>
Date: Wed, 23 Feb 2022 18:22:29 -0500
Subject: [PATCH 30/30] Edits from code review

---
 emcc.py            | 10 ++++------
 tests/test_core.py |  1 +
 2 files changed, 5 insertions(+), 6 deletions(-)

diff --git a/emcc.py b/emcc.py
index 4e15c949f80d..483bb7d53acf 100755
--- a/emcc.py
+++ b/emcc.py
@@ -2074,12 +2074,10 @@ def default_setting(name, new_default):
   else:
     settings.JS_LIBRARIES.append((0, 'library_pthread_stub.js'))
 
-  if (
-      '$formatException' in settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE or
-      settings.INCLUDE_FULL_LIBRARY and not settings.DISABLE_EXCEPTION_CATCHING
-  ):
-    settings.DEFAULT_LIBRARY_FUNCS_TO_INCLUDE += ['$formatException']
-    settings.EXPORTED_FUNCTIONS += ['formatException', '_emscripten_format_exception', '_free']
+  # 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']
 
   if settings.FORCE_FILESYSTEM and not settings.MINIMAL_RUNTIME:
     # when the filesystem is forced, we export by default methods that filesystem usage
diff --git a/tests/test_core.py b/tests/test_core.py
index 6c42691f6c41..8e4f273207d3 100644
--- a/tests/test_core.py
+++ b/tests/test_core.py
@@ -1546,6 +1546,7 @@ def test_exceptions_rethrow_missing(self):
   def test_format_exception(self):
     self.set_setting('DISABLE_EXCEPTION_CATCHING', 0)
     self.set_setting('DEFAULT_LIBRARY_FUNCS_TO_INCLUDE', ['$formatException'])
+    self.set_setting('EXPORTED_FUNCTIONS', ['_main', 'formatException', '_emscripten_format_exception', '_free'])
     self.maybe_closure()
     src = '''
       #include <emscripten.h>