hphp/runtime/vm/unwind.h

   1 /*
   2    +----------------------------------------------------------------------+
   3    | HipHop for PHP                                                       |
   4    +----------------------------------------------------------------------+
   5    | Copyright (c) 2010-2014 Facebook, Inc. (http://www.facebook.com)     |
   6    +----------------------------------------------------------------------+
   7    | This source file is subject to version 3.01 of the PHP license,      |
   8    | that is bundled with this package in the file LICENSE, and is        |
   9    | available through the world-wide-web at the following url:           |
  10    | http://www.php.net/license/3_01.txt                                  |
  11    | If you did not receive a copy of the PHP license and are unable to   |
  12    | obtain it through the world-wide-web, please send a note to          |
  13    | license@php.net so we can mail you a copy immediately.               |
  14    +----------------------------------------------------------------------+
  15 */
  16 #ifndef incl_HPHP_UNWIND_H_
  17 #define incl_HPHP_UNWIND_H_
  18
  19 #include <stdexcept>
  20
  21 namespace HPHP {
  22
  23 //////////////////////////////////////////////////////////////////////
  24
  25 /*
  26  * Enumerates actions that should be taken by the enterVM loop after
  27  * unwinding an exception.
  28  */
  29 enum class UnwindAction {
  30   /*
  31    * The exception was not handled in this nesting of the VM---it
  32    * needs to be rethrown.
  33    */
  34   Propagate,
  35
  36   /*
  37    * A catch or fault handler was identified and the VM state has been
  38    * prepared for entry to it.
  39    */
  40   ResumeVM,
  41
  42   /**
  43    * An exception thrown from an eagerly executed async function was
  44    * wrapped into a StaticExceptionWaitHandle. The async function was
  45    * running in the top frame, so we need to return from the VM instance.
  46    */
  47   Return,
  48 };
  49
  50 /*
  51  * The main entry point to the unwinder.
  52  *
  53  * When an exception propagates up to the top-level try/catch in
  54  * enterVM, it calls to this module to perform stack unwinding as
  55  * appropriate.  This function must be called from within the catch
  56  * handler (it rethrows the exception to determine what to do).
  57  *
  58  * The returned UnwindAction instructs enterVM on how to proceed.
  59  */
  60 UnwindAction exception_handler() noexcept;
  61
  62 //////////////////////////////////////////////////////////////////////
  63
  64 /*
  65  * This exception is thrown when executing an Unwind bytecode, which
  66  * will reraise the current fault and resume propagating it.
  67  */
  68 struct VMPrepareUnwind : std::exception {
  69   const char* what() const throw() { return "VMPrepareUnwind"; }
  70 };
  71
  72 /*
  73  * Thrown when we need to "switch modes" by re-starting the current VM
  74  * invocation.  For example, if we need to break for the debugger, or
  75  * enable code coverage mode.
  76  */
  77 struct VMSwitchMode : std::exception {
  78   const char* what() const throw() { return "VMSwitchMode"; }
  79 };
  80
  81 /*
  82  * Thrown for stack overflow thrown from a prolog while
  83  * re-entering
  84  */
  85 struct VMReenterStackOverflow : std::exception {
  86   const char* what() const throw() { return "VMReenterStackOverflow"; }
  87 };
  88
  89 /*
  90  * Same as VMSwitchMode, except for use from a builtin---the frame for
  91  * the builtin function should be unwound before resuming the VM.
  92  */
  93 struct VMSwitchModeBuiltin : std::exception {
  94   const char* what() const throw() { return "VMSwitchModeBuiltin"; }
  95 };
  96
  97 //////////////////////////////////////////////////////////////////////
  98
  99 }
 100
 101 #endif