• julien.gilli's avatar
    Add SetAbortOnUncaughtExceptionCallback API · 1ee712ab
    julien.gilli authored
    The --abort-on-uncaught-exception command line switch makes
    Isolate::Throw abort if the error being thrown cannot be caught by a
    try/catch block.
    
    Embedders may want to use other mechanisms than try/catch blocks to
    handle uncaught exceptions. For instance, Node.js has "domain" objects
    that have error handlers that can handle uncaught exception like
    following:
    
    var d = domain.create();
    
    d.on('error', function onError(err) {
      console.log('Handling error');
    });
    
    d.run(function() {
      throw new Error("boom");
    });
    
    These error handlers are called by isolates' message listeners.
    
    If --abort-on-uncaught-exception is *not* used, the isolate's
    message listener will be called, which will in turn call the domain's
    error handler. The process will output 'Handling error' and will exit
    successfully (not due to an uncaught exception). This is the behavior
    that Node.js users expect.
    
    However, if --abort-on-uncaught-exception is used and when throwing an
    error within a domain that has an error handler, the process will abort
    and the domain's error handler will not be called. This is not the
    behavior that Node.js users expect.
    
    Having a SetAbortOnUncaughtExceptionCallback API allows embedders to
    determine when it's not appropriate to abort and instead handle the
    exception via the isolate's message listener.
    
    In the example above, Node.js would set a custom callback with
    SetAbortOnUncaughtExceptionCallback that would be implemented as
    following (the sample code has been simplified to remove what's not
    relevant to this change):
    
    bool ShouldAbortOnUncaughtException(Isolate* isolate) {
      return !IsDomainActive();
    }
    
    Now when --abort-on-uncaught-exception is used, Isolate::Throw would
    call that callback and determine that it should not abort if a domain
    with an error handler is active. Instead, the isolate's message listener
    would be called and the error would be handled by the domain's error
    handler.
    
    I believe this can also be useful for other embedders.
    
    BUG=
    
    R=bmeurer@chromium.org
    
    Review URL: https://codereview.chromium.org/1375933003
    
    Cr-Commit-Position: refs/heads/master@{#31111}
    1ee712ab
isolate.h 51.7 KB