Exceptions.h

#pragma once

#include <exception>
#include <stdexcept>
#include <string>

#include <torch/csrc/THP_export.h>
#include <c10/util/Exception.h>
#include <torch/csrc/utils/auto_gil.h>
#include <torch/csrc/utils/object_ptr.h>
#include <torch/csrc/WindowsTorchApiMacro.h>

#define HANDLE_TH_ERRORS                                                       \
  try {
#define END_HANDLE_TH_ERRORS_RET(retval)                           \
  }                                                                \
  catch (python_error & e) {                                       \
    return retval;                                                 \
  }                                                                \
  catch (const c10::IndexError& e) {                               \
    auto msg = torch::processErrorMsg(e.what_without_backtrace()); \
    PyErr_SetString(PyExc_IndexError, msg.c_str());                \
    return retval;                                                 \
  }                                                                \
  catch (const c10::Error& e) {                                    \
    auto msg = torch::processErrorMsg(e.what_without_backtrace()); \
    PyErr_SetString(PyExc_RuntimeError, msg.c_str());              \
    return retval;                                                 \
  }                                                                \
  catch (torch::PyTorchError & e) {                                \
    auto msg = torch::processErrorMsg(e.what());                   \
    PyErr_SetString(e.python_type(), msg.c_str());                 \
    return retval;                                                 \
  }                                                                \
  catch (const std::exception& e) {                                \
    auto msg = torch::processErrorMsg(e.what());                   \
    PyErr_SetString(PyExc_RuntimeError, msg.c_str());              \
    return retval;                                                 \
  }

#define END_HANDLE_TH_ERRORS END_HANDLE_TH_ERRORS_RET(nullptr)

extern PyObject *THPException_FatalError;

// Throwing this exception means that the python error flags have been already
// set and control should be immediately returned to the interpreter.
struct python_error : public std::exception {
  python_error() : type(nullptr), value(nullptr), traceback(nullptr) {}

  python_error(const python_error &other) : type(other.type), value(other.value), traceback(other.traceback) {
    AutoGIL gil;
    Py_XINCREF(type);
    Py_XINCREF(value);
    Py_XINCREF(traceback);
  }

  python_error(python_error&& other) {
    type = other.type;
    value = other.value;
    traceback = other.traceback;
    other.type = nullptr;
    other.value = nullptr;
    other.traceback = nullptr;
  }

  ~python_error() override {
    if (type || value || traceback) {
      AutoGIL gil;
      Py_XDECREF(type);
      Py_XDECREF(value);
      Py_XDECREF(traceback);
    }
  }

  inline void persist() {
    if (type) return; // Don't overwrite exceptions
    // PyErr_Fetch overwrites the pointers
    AutoGIL gil;
    Py_XDECREF(type);
    Py_XDECREF(value);
    Py_XDECREF(traceback);
    PyErr_Fetch(&type, &value, &traceback);
  }

  inline void restore() {
    if (!type) return;
    // PyErr_Restore steals references
    AutoGIL gil;
    Py_XINCREF(type);
    Py_XINCREF(value);
    Py_XINCREF(traceback);
    PyErr_Restore(type, value, traceback);
  }

  PyObject* type;
  PyObject* value;
  PyObject* traceback;
};

#ifdef _THP_CORE

bool THPException_init(PyObject *module);
#endif

namespace torch {

THP_CLASS std::string processErrorMsg(std::string str);

// Abstract base class for exceptions which translate to specific Python types
struct PyTorchError : public std::exception {
  virtual PyObject* python_type() = 0;
  const char* what() const noexcept override {
    return msg.c_str();
  }
  std::string msg;
};

// Translates to Python IndexError
struct IndexError : public PyTorchError {
  IndexError(const char *format, ...);
  PyObject* python_type() override {
    return PyExc_IndexError;
  }
};

// Translates to Python TypeError
struct TypeError : public PyTorchError {
  TORCH_API TypeError(const char *format, ...);
  PyObject* python_type() override {
    return PyExc_TypeError;
  }
};

// Translates to Python ValueError
struct ValueError : public PyTorchError {
  ValueError(const char *format, ...);
  PyObject* python_type() override {
    return PyExc_ValueError;
  }
};

} // namespace torch