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# rt.dwarfeh

Exception handling support for Dwarf-style portable exceptions.
License:
Distributed under the Boost Software License 1.0. (See accompanying file LICENSE)
Authors:
Walter Bright

Source src/rt/dwarfeh.d

struct `ExceptionHeader`;
  Wrap the unwinder's data with our own compiler specific struct with our own data.
  static @nogc ExceptionHeader* `create`(Throwable `o`);
    Allocate and initialize an ExceptionHeader.
    Parameters:

    Throwable `o` | thrown object

    Returns:
    allocated and initalized ExceptionHeader
  static void `free`(ExceptionHeader* `eh`);
    Free ExceptionHeader that was created by create().
    Parameters:

    ExceptionHeader* `eh` | ExceptionHeader to `free`

  void `push`();
    Push this onto stack of chained exceptions.
  static ExceptionHeader* `pop`();
    Pop and return top of chained exception stack.
  static ExceptionHeader* `toExceptionHeader`(_Unwind_Exception* `eo`);
    Convert from pointer to exception_object to pointer to ExceptionHeader that it is embedded inside of.
    Parameters:

    _Unwind_Exception* `eo` | pointer to exception_object field

    Returns:
    pointer to ExceptionHeader that `eo` points into.
Throwable `__dmd_begin_catch`(_Unwind_Exception* `exceptionObject`);
  The first thing a catch handler does is call this.
  Parameters:

  _Unwind_Exception* `exceptionObject` | value passed to catch handler by unwinder

  Returns:
  object that was caught
nothrow @nogc void* `_d_eh_swapContextDwarf`(void* `newContext`);
  Called when fibers switch contexts.
  Parameters:

  void* `newContext` | stack to switch to

  Returns:
  previous value of stack
void `_d_throwdwarf`(Throwable `o`);
  Called by D code to throw an exception via

      throw o;

  Parameters:

  Throwable `o` | Object to throw

  Returns:
  doesn't return
_Unwind_Reason_Code `__dmd_personality_v0`(int `ver`, _Unwind_Action `actions`, _Unwind_Exception_Class `exceptionClass`, _Unwind_Exception* `exceptionObject`, _Unwind_Context* `context`);
  "personality" function, specific to each language. This one, of course, is specific to DMD.
  Parameters:

  int `ver` | version must be 1
  _Unwind_Action `actions` | bitwise OR of the 4 `actions` UA_xxx. UA_SEARCH_PHASE means return URC_HANDLER_FOUND if current frame has a handler, URC_CONTINUE_UNWIND if not. Cannot be used with UA_CLEANUP_PHASE. UA_CLEANUP_PHASE means perform cleanup for current frame by calling nested functions and returning URC_CONTINUE_UNWIND. Or, set up registers and IP for Landing Pad and return URC_INSTALL_CONTEXT. UA_HANDLER_FRAME means this frame was the one with the handler in Phase 1, and now it is Phase 2 and the handler must be run. UA_FORCE_UNWIND means unwinding the stack for longjmp or thread cancellation. Run finally clauses, not catch clauses, finallys must end with call to Uwind_Resume().
  _Unwind_Exception_Class `exceptionClass` | 8 byte value indicating type of thrown exception. If the low 4 bytes are "C++\0", it's a C++ exception.
  _Unwind_Exception* `exceptionObject` | language specific exception information
  _Unwind_Context* `context` | opaque type of unwinder state information

  Returns:
  reason code
  See Also:
  http://www.ucw.cz/~hubicka/papers/abi/node25.html
ClassInfo `getClassInfo`(_Unwind_Exception* `exceptionObject`);
  Look at the chain of inflight exceptions and pick the class type that'll be looked for in catch clauses.
  Parameters:

  _Unwind_Exception* `exceptionObject` | language specific exception information

  Returns:
  class type to look for
_uleb128_t `uLEB128`(const(ubyte)** `p`);
  Decode Unsigned LEB128.
  Parameters:

  const(ubyte)** `p` | pointer to data pointer, *`p` is updated to point past decoded value

  Returns:
  decoded value
  See Also:
  https://en.wikipedia.org/wiki/LEB128
_sleb128_t `sLEB128`(const(ubyte)** `p`);
  Decode Signed LEB128.
  Parameters:

  const(ubyte)** `p` | pointer to data pointer, *`p` is updated to point past decoded value

  Returns:
  decoded value
  See Also:
  https://en.wikipedia.org/wiki/LEB128
LsdaResult `scanLSDA`(const(ubyte)* `lsda`, _Unwind_Ptr `ip`, _Unwind_Exception_Class `exceptionClass`, bool `cleanupsOnly`, bool `preferHandler`, _Unwind_Exception* `exceptionObject`, out _Unwind_Ptr `landingPad`, out int `handler`);
  Read and extract information from the LSDA (aka gcc_except_table section). The dmd Call Site Table is structurally different from other implementations. It is organized as nested ranges, and one `ip` can map to multiple ranges. The most nested candidate is selected when searched. Other implementations have one candidate per `ip`.
  Parameters:

  const(ubyte)* `lsda` | pointer to LSDA table
  _Unwind_Ptr `ip` | offset from start of function at which exception happened
  _Unwind_Exception_Class `exceptionClass` | which language threw the exception
  bool `cleanupsOnly` | only look for cleanups
  bool `preferHandler` | if a `handler` encloses a cleanup, prefer the `handler`
  _Unwind_Exception* `exceptionObject` | language specific exception information
  _Unwind_Ptr `landingPad` | set to landing pad
  int `handler` | set to index of which catch clause was matched

  Returns:
  LsdaResult
  See Also:
  http://reverseengineering.stackexchange.com/questions/6311/how-to-recover-the-exception-info-from-gcc-except-table-and-eh-handle-sections http://www.airs.com/blog/archives/464 https://anarcheuz.github.io/2015/02/15/ELF%20internals%20part%202%20-%20exception%20handling/
int `actionTableLookup`(_Unwind_Exception* `exceptionObject`, uint `actionRecordPtr`, const(ubyte)* `pActionTable`, const(ubyte)* `tt`, ubyte `TType`, _Unwind_Exception_Class `exceptionClass`);
  Look up classType in Action Table.
  Parameters:

  _Unwind_Exception* `exceptionObject` | language specific exception information
  uint `actionRecordPtr` | starting index in Action Table + 1
  const(ubyte)* `pActionTable` | pointer to start of Action Table
  const(ubyte)* `tt` | pointer past end of Type Table
  ubyte `TType` | encoding of entries in Type Table
  _Unwind_Exception_Class `exceptionClass` | which language threw the exception

  Returns:
  >=1 means the handler index of the classType 0 means classType is not in the Action Table <0 means corrupt
enum _Unwind_Exception_Class `cppExceptionClass`;
  C++ Support
void* `getCppPtrToThrownObject`(_Unwind_Exception* `exceptionObject`, CppTypeInfo `sti`);
  Get Pointer to Thrown Object if type of thrown object is implicitly convertible to the catch type.
  Parameters:

  _Unwind_Exception* `exceptionObject` | language specific exception information
  CppTypeInfo `sti` | type of catch clause

  Returns:
  `null` if not caught, pointer to thrown object if caught
interface `CppTypeInfo`;
  Access C++ std::type_info's virtual functions from D, being careful to not require linking with libstd++ or interfere with core.stdcpp.typeinfo. So, give it a different name.
struct `CppExceptionHeader`;
  The C++ version of D's ExceptionHeader wrapper
  static CppExceptionHeader* `toExceptionHeader`(_Unwind_Exception* `eo`);
    Convert from pointer to exception_object field to pointer to CppExceptionHeader that it is embedded inside of.
    Parameters:

    _Unwind_Exception* `eo` | pointer to exception_object field

    Returns:
    pointer to CppExceptionHeader that `eo` points into.

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