ruby_exceptions.hpp

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#ifndef Exc_Ruby__Ruby_Exceptions__hpp_
#define Exc_Ruby__Ruby_Exceptions__hpp_

#include <ruby.h>
#undef TYPE

#include <stdexcept>
#include "detail/ruby_hacks.hpp"

namespace Exc_Ruby
{


struct Ruby_Exception
{
  Ruby_Exception(VALUE e) : ex(e) { }

  Ruby_Exception(VALUE exc, char const * fmt, ...);

  VALUE ex;
};


struct Ruby_Jump_Tag
{
  Ruby_Jump_Tag(int t) : tag(t) { }

  int tag;
};

// Goto is used here to avoid having to use a second try/catch block (can't
// rb_exc_raise directly out of the catch blocks below, since the exceptions
// will not get properly cleaned up).
// The gotos are located before the try and not after it so the function can't
// "fall through" into the exception-handling code accidentally.
#define RUBY_TRY \
  VALUE Exc_Ruby__ruby_exc = Qnil; \
  int Exc_Ruby__ruby_jump_tag = 0; \
  \
  goto start_of_RUBY_TRY; \
  \
  Exc_Ruby__ruby_exception: \
    rb_exc_raise(Exc_Ruby__ruby_exc); \
  Exc_Ruby__ruby_jump_tag: \
    rb_jump_tag(Exc_Ruby__ruby_jump_tag); \
  \
  start_of_RUBY_TRY: \
  try

#define RUBY_RETHROW(ex) \
  Exc_Ruby__ruby_exc = ex; \
  goto Exc_Ruby__ruby_exception;

#define RUBY_CATCH \
  catch(::Exc_Ruby::Ruby_Exception const & ex) \
  { \
    RUBY_RETHROW(ex.ex); \
  } \
  catch(::Exc_Ruby::Ruby_Jump_Tag const & ex) \
  { \
    Exc_Ruby__ruby_jump_tag = ex.tag; \
    goto Exc_Ruby__ruby_jump_tag; \
  } \
  catch(std::bad_alloc const & ex) \
  { \
    /* This won't work quite right if the rb_exc_new2 fails; not    */ \
    /* much we can do about that, since Ruby doesn't give us access */ \
    /* to a pre-allocated NoMemoryError object                      */ \
    RUBY_RETHROW(rb_exc_new2(rb_eNoMemError, ex.what())); \
  } \
  catch(std::exception const & ex) \
  { \
    /* This can raise a NoMemoryError in VERY rare circumstances    */ \
    RUBY_RETHROW(rb_exc_new2(rb_eRuntimeError, ex.what())); \
  } \
  catch(...) \
  { \
    RUBY_RETHROW(rb_exc_new2(rb_eRuntimeError, "unknown C++ exception thrown")); \
  } \

} // namespace Exc_Ruby

#include "ruby_exceptions.ipp"

#endif // Exc_Ruby__Ruby_Exceptions__hpp_

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