[EH] Add more explanation to EXPORT_EXCEPTION_HANDLING_HELPERS deprecation (#26517)

Like WebAssembly/binaryen#8507, there can be
people who use this methods at `-O1` or above. This adds more
explanation of the workaround in ChangeeLog, site docs, and the
deprecation message. You don't strictly need
`decrementExceptionRefcount` to use `getExceptionMessage`, but you need
it if you care about asan, because exceptions thrown in Wasm and caught
in JS don't get freed unless you explicitly decrement the refcount.

Author: aheejin

ChangeLog.md

@@ -22,7 +22,10 @@ See docs/process.md for more on how version tagging works.
 ----------------------
 - `EXPORT_EXCEPTION_HANDLING_HELPERS` is deprecated and setting it will not do
   anything. `getExceptionMessage` is exported anyway when `ASSERTIONS` or
-  `EXCEPTION_STACK_TRACES` is set, which are set by default at `-O0`. (#26499)
+  `EXCEPTION_STACK_TRACES` is set, which are set by default at `-O0`. At `-O1`
+  or above, you can export it separately by
+  `-sEXPORTED_RUNTIME_METHODS=getExceptionMessage,decrementExceptionRefcount`.
+  (#26499)
 - The deprecated `EMSCRIPTEN` macro is now defined in `emscripten.h` rather than
   on the command line (`__EMSCRIPTEN__`, which is built into LLVM, should be
   used instead). (#26417)

site/source/docs/porting/exceptions.rst

@@ -146,7 +146,8 @@ exception thrown``, this code will print ``MyException,My exception thrown``.
 
 ``getExceptionMessage`` is available when exceptions are used and either
 ``-sASSERTIONS`` or ``-sEXCEPTION_STACK_TRACES`` is set, which are by default
-true at ``-O0``.
+true at ``-O0``.  At ``-O1`` or above, you can export it separately by
+``-sEXPORTED_RUNTIME_METHODS=getExceptionMessage,decrementExceptionRefcount``.
 
 If the stack pointer has been moved due to stack allocations within the Wasm
 function before an exception is thrown, you can use ``stackSave()`` and

site/source/docs/tools_reference/settings_reference.rst

@@ -3419,7 +3419,7 @@ these settings please open a bug (or reply to one of the existing bugs).
  - ``LEGALIZE_JS_FFI``: to disable JS type legalization use `-sWASM_BIGINT` or `-sSTANDALONE_WASM`
  - ``ASYNCIFY_EXPORTS``: please use JSPI_EXPORTS instead
  - ``LINKABLE``: under consideration for removal (https://github.com/emscripten-core/emscripten/issues/25262)
- - ``EXPORT_EXCEPTION_HANDLING_HELPERS``: getExceptionMessage is automatically exported when ASSERTIONS or EXCEPTION_STACK_TRACES is 1 and throw is used
+ - ``EXPORT_EXCEPTION_HANDLING_HELPERS``: getExceptionMessage is exported anyway when ASSERTIONS or EXCEPTION_STACK_TRACES is set, which are set by default at -O0. At -O1 or above, you can export it separately by -sEXPORTED_RUNTIME_METHODS=getExceptionMessage,decrementExceptionRefcount.
 
 .. _legacy-settings:
 

tools/settings.py

@@ -114,7 +114,7 @@
     'LEGALIZE_JS_FFI': 'to disable JS type legalization use `-sWASM_BIGINT` or `-sSTANDALONE_WASM`',
     'ASYNCIFY_EXPORTS': 'please use JSPI_EXPORTS instead',
     'LINKABLE': 'under consideration for removal (https://github.com/emscripten-core/emscripten/issues/25262)',
-    'EXPORT_EXCEPTION_HANDLING_HELPERS': 'getExceptionMessage is automatically exported when ASSERTIONS or EXCEPTION_STACK_TRACES is 1 and throw is used',
+    'EXPORT_EXCEPTION_HANDLING_HELPERS': 'getExceptionMessage is exported anyway when ASSERTIONS or EXCEPTION_STACK_TRACES is set, which are set by default at -O0. At -O1 or above, you can export it separately by -sEXPORTED_RUNTIME_METHODS=getExceptionMessage,decrementExceptionRefcount.',
 }
 
 # Settings that don't need to be externalized when serializing to json because they