base/mac/scoped_nsexception_enabler.h

   1 // Copyright (c) 2011 The Chromium Authors. All rights reserved.
   2 // Use of this source code is governed by a BSD-style license that can be
   3 // found in the LICENSE file.
   4
   5 #ifndef BASE_MAC_SCOPED_NSEXCEPTION_ENABLER_H_
   6 #define BASE_MAC_SCOPED_NSEXCEPTION_ENABLER_H_
   7
   8 #import <Foundation/Foundation.h>
   9
  10 #include "base/base_export.h"
  11 #include "base/basictypes.h"
  12
  13 namespace base {
  14 namespace mac {
  15
  16 // BrowserCrApplication attempts to restrict throwing of NSExceptions
  17 // because they interact badly with C++ scoping rules.  Unfortunately,
  18 // there are some cases where exceptions must be supported, such as
  19 // when third-party printer drivers are used.  These helpers can be
  20 // used to enable exceptions for narrow windows.
  21
  22 // Make it easy to safely allow NSException to be thrown in a limited
  23 // scope.  Note that if an exception is thrown, then this object will
  24 // not be appropriately destructed!  If the exception ends up in the
  25 // top-level event loop, things are cleared in -reportException:.  If
  26 // the exception is caught at a lower level, a higher level scoper
  27 // should eventually reset things.
  28 class BASE_EXPORT ScopedNSExceptionEnabler {
  29  public:
  30   ScopedNSExceptionEnabler();
  31   ~ScopedNSExceptionEnabler();
  32
  33  private:
  34   bool was_enabled_;
  35
  36   DISALLOW_COPY_AND_ASSIGN(ScopedNSExceptionEnabler);
  37 };
  38
  39 // Access the exception setting for the current thread.  This is for
  40 // the support code in BrowserCrApplication, other code should use
  41 // the scoper.
  42 BASE_EXPORT bool GetNSExceptionsAllowed();
  43 BASE_EXPORT void SetNSExceptionsAllowed(bool allowed);
  44
  45 // Executes |block| with fatal-exceptions turned off, and returns the
  46 // result.  If an exception is thrown during the perform, nil is
  47 // returned.
  48 typedef id (^BlockReturningId)();
  49 BASE_EXPORT id RunBlockIgnoringExceptions(BlockReturningId block);
  50
  51 }  // namespace mac
  52 }  // namespace base
  53
  54 #endif  // BASE_MAC_SCOPED_NSEXCEPTION_ENABLER_H_