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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 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`, const(ubyte)* `currentLsd`);
  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
  const(ubyte)* `currentLsd` | pointer to LSDA table

  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`, const(ubyte)* `lsda`);
  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
  const(ubyte)* `lsda` | pointer to LSDA table

  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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