pythonrun.c

/* Top level execution of Python code (including in __main__) */

/* To help control the interfaces between the startup, execution and
 * shutdown code, the phases are split across separate modules (bootstrap,
 * pythonrun, shutdown)
 */

/* TODO: Cull includes following phase split */

#include "Python.h"

#include "pycore_ast.h"           // PyAST_mod2obj()
#include "pycore_audit.h"         // _PySys_Audit()
#include "pycore_ceval.h"         // _Py_EnterRecursiveCall()
#include "pycore_compile.h"       // _PyAST_Compile()
#include "pycore_fileutils.h"     // _PyFile_Flush
#include "pycore_import.h"        // _PyImport_GetImportlibExternalLoader()
#include "pycore_interp.h"        // PyInterpreterState.importlib
#include "pycore_object.h"        // _PyDebug_PrintTotalRefs()
#include "pycore_parser.h"        // _PyParser_ASTFromString()
#include "pycore_pyerrors.h"      // _PyErr_GetRaisedException()
#include "pycore_pylifecycle.h"   // _Py_FdIsInteractive()
#include "pycore_pystate.h"       // _PyInterpreterState_GET()
#include "pycore_pythonrun.h"     // export _PyRun_InteractiveLoopObject()
#include "pycore_sysmodule.h"     // _PySys_SetAttr()
#include "pycore_traceback.h"     // _PyTraceBack_Print()
#include "pycore_unicodeobject.h" // _PyUnicode_Equal()

#include "errcode.h"              // E_EOF
#include "marshal.h"              // PyMarshal_ReadLongFromFile()

#include <stdbool.h>

#ifdef MS_WINDOWS
#  include "malloc.h"             // alloca()
#endif

#ifdef MS_WINDOWS
#  undef BYTE
#  include "windows.h"
#endif

/* Forward */
static void flush_io(void);
static PyObject *run_mod(mod_ty, PyObject *, PyObject *, PyObject *,
                          PyCompilerFlags *, PyArena *, PyObject*, int);
static PyObject *run_pyc_file(FILE *, PyObject *, PyObject *,
                              PyCompilerFlags *);
static int PyRun_InteractiveOneObjectEx(FILE *, PyObject *, PyCompilerFlags *);
static PyObject* pyrun_file(FILE *fp, PyObject *filename, int start,
                            PyObject *globals, PyObject *locals, int closeit,
                            PyCompilerFlags *flags);
static PyObject *
_PyRun_StringFlagsWithName(const char *str, PyObject* name, int start,
                           PyObject *globals, PyObject *locals, PyCompilerFlags *flags,
                           int generate_new_source);

int
_PyRun_AnyFileObject(FILE *fp, PyObject *filename, int closeit,
                     PyCompilerFlags *flags)
{
    int decref_filename = 0;
    if (filename == NULL) {
        filename = PyUnicode_FromString("???");
        if (filename == NULL) {
            PyErr_Print();
            return -1;
        }
        decref_filename = 1;
    }

    int res;
    if (_Py_FdIsInteractive(fp, filename)) {
        res = _PyRun_InteractiveLoopObject(fp, filename, flags);
        if (closeit) {
            fclose(fp);
        }
    }
    else {
        res = _PyRun_SimpleFileObject(fp, filename, closeit, flags);
    }

    if (decref_filename) {
        Py_DECREF(filename);
    }
    return res;
}

int
PyRun_AnyFileExFlags(FILE *fp, const char *filename, int closeit,
                     PyCompilerFlags *flags)
{
    PyObject *filename_obj = NULL;
    if (filename != NULL) {
        filename_obj = PyUnicode_DecodeFSDefault(filename);
        if (filename_obj == NULL) {
            PyErr_Print();
            return -1;
        }
    }
    int res = _PyRun_AnyFileObject(fp, filename_obj, closeit, flags);
    Py_XDECREF(filename_obj);
    return res;
}


int
_PyRun_InteractiveLoopObject(FILE *fp, PyObject *filename, PyCompilerFlags *flags)
{
    PyCompilerFlags local_flags = _PyCompilerFlags_INIT;
    if (flags == NULL) {
        flags = &local_flags;
    }

    PyObject *v;
    if (PySys_GetOptionalAttr(&_Py_ID(ps1), &v) < 0) {
        PyErr_Print();
        return -1;
    }
    if (v == NULL) {
        v = PyUnicode_FromString(">>> ");
        if (v == NULL) {
            PyErr_Clear();
        }
        if (_PySys_SetAttr(&_Py_ID(ps1), v) < 0) {
            PyErr_Clear();
        }
    }
    Py_XDECREF(v);
    if (PySys_GetOptionalAttr(&_Py_ID(ps2), &v) < 0) {
        PyErr_Print();
        return -1;
    }
    if (v == NULL) {
        v = PyUnicode_FromString("... ");
        if (v == NULL) {
            PyErr_Clear();
        }
        if (_PySys_SetAttr(&_Py_ID(ps2), v) < 0) {
            PyErr_Clear();
        }
    }
    Py_XDECREF(v);

#ifdef Py_REF_DEBUG
    int show_ref_count = _Py_GetConfig()->show_ref_count;
#endif
    int err = 0;
    int ret;
    int nomem_count = 0;
    do {
        ret = PyRun_InteractiveOneObjectEx(fp, filename, flags);
        if (ret == -1 && PyErr_Occurred()) {
            /* Prevent an endless loop after multiple consecutive MemoryErrors
             * while still allowing an interactive command to fail with a
             * MemoryError. */
            if (PyErr_ExceptionMatches(PyExc_MemoryError)) {
                if (++nomem_count > 16) {
                    PyErr_Clear();
                    err = -1;
                    break;
                }
            } else {
                nomem_count = 0;
            }
            PyErr_Print();
            flush_io();
        } else {
            nomem_count = 0;
        }
#ifdef Py_REF_DEBUG
        if (show_ref_count) {
            _PyDebug_PrintTotalRefs();
        }
#endif
    } while (ret != E_EOF);
    return err;
}


int
PyRun_InteractiveLoopFlags(FILE *fp, const char *filename, PyCompilerFlags *flags)
{
    PyObject *filename_obj = PyUnicode_DecodeFSDefault(filename);
    if (filename_obj == NULL) {
        PyErr_Print();
        return -1;
    }

    int err = _PyRun_InteractiveLoopObject(fp, filename_obj, flags);
    Py_DECREF(filename_obj);
    return err;

}


// Call _PyParser_ASTFromFile() with sys.stdin.encoding, sys.ps1 and sys.ps2
static int
pyrun_one_parse_ast(FILE *fp, PyObject *filename,
                    PyCompilerFlags *flags, PyArena *arena,
                    mod_ty *pmod, PyObject** interactive_src)
{
    // Get sys.stdin.encoding (as UTF-8)
    PyObject *attr;
    PyObject *encoding_obj = NULL;
    const char *encoding = NULL;
    if (fp == stdin) {
        if (PySys_GetOptionalAttr(&_Py_ID(stdin), &attr) < 0) {
            PyErr_Clear();
        }
        else if (attr != NULL && attr != Py_None) {
            if (PyObject_GetOptionalAttr(attr, &_Py_ID(encoding), &encoding_obj) < 0) {
                PyErr_Clear();
            }
            else if (encoding_obj && PyUnicode_Check(encoding_obj)) {
                encoding = PyUnicode_AsUTF8(encoding_obj);
                if (!encoding) {
                    PyErr_Clear();
                }
            }
        }
        Py_XDECREF(attr);
    }

    // Get sys.ps1 (as UTF-8)
    PyObject *ps1_obj = NULL;
    const char *ps1 = "";
    if (PySys_GetOptionalAttr(&_Py_ID(ps1), &attr) < 0) {
        PyErr_Clear();
    }
    else if (attr != NULL) {
        ps1_obj = PyObject_Str(attr);
        Py_DECREF(attr);
        if (ps1_obj == NULL) {
            PyErr_Clear();
        }
        else if (PyUnicode_Check(ps1_obj)) {
            ps1 = PyUnicode_AsUTF8(ps1_obj);
            if (ps1 == NULL) {
                PyErr_Clear();
                ps1 = "";
            }
        }
    }

    // Get sys.ps2 (as UTF-8)
    PyObject *ps2_obj = NULL;
    const char *ps2 = "";
    if (PySys_GetOptionalAttr(&_Py_ID(ps2), &attr) < 0) {
        PyErr_Clear();
    }
    else if (attr != NULL) {
        ps2_obj = PyObject_Str(attr);
        Py_DECREF(attr);
        if (ps2_obj == NULL) {
            PyErr_Clear();
        }
        else if (PyUnicode_Check(ps2_obj)) {
            ps2 = PyUnicode_AsUTF8(ps2_obj);
            if (ps2 == NULL) {
                PyErr_Clear();
                ps2 = "";
            }
        }
    }

    int errcode = 0;
    *pmod = _PyParser_InteractiveASTFromFile(fp, filename, encoding,
                                             Py_single_input, ps1, ps2,
                                             flags, &errcode, interactive_src, arena);
    Py_XDECREF(ps1_obj);
    Py_XDECREF(ps2_obj);
    Py_XDECREF(encoding_obj);

    if (*pmod == NULL) {
        if (errcode == E_EOF) {
            PyErr_Clear();
            return E_EOF;
        }
        return -1;
    }
    return 0;
}


/* A PyRun_InteractiveOneObject() auxiliary function that does not print the
 * error on failure. */
static int
PyRun_InteractiveOneObjectEx(FILE *fp, PyObject *filename,
                             PyCompilerFlags *flags)
{
    PyArena *arena = _PyArena_New();
    if (arena == NULL) {
        return -1;
    }

    mod_ty mod;
    PyObject *interactive_src;
    int parse_res = pyrun_one_parse_ast(fp, filename, flags, arena, &mod, &interactive_src);
    if (parse_res != 0) {
        _PyArena_Free(arena);
        return parse_res;
    }

    PyObject *main_module = PyImport_AddModuleRef("__main__");
    if (main_module == NULL) {
        _PyArena_Free(arena);
        return -1;
    }
    PyObject *main_dict = PyModule_GetDict(main_module);  // borrowed ref

    PyObject *res = run_mod(mod, filename, main_dict, main_dict, flags, arena, interactive_src, 1);
    Py_INCREF(interactive_src);
    _PyArena_Free(arena);
    Py_DECREF(main_module);
    if (res == NULL) {
        PyThreadState *tstate = _PyThreadState_GET();
        PyObject *exc = _PyErr_GetRaisedException(tstate);
        if (PyType_IsSubtype(Py_TYPE(exc),
                             (PyTypeObject *) PyExc_SyntaxError))
        {
            /* fix "text" attribute */
            assert(interactive_src != NULL);
            PyObject *xs = PyUnicode_Splitlines(interactive_src, 1);
            if (xs == NULL) {
                goto error;
            }
            PyObject *exc_lineno = PyObject_GetAttr(exc, &_Py_ID(lineno));
            if (exc_lineno == NULL) {
                Py_DECREF(xs);
                goto error;
            }
            int n = PyLong_AsInt(exc_lineno);
            Py_DECREF(exc_lineno);
            if (n <= 0 || n > PyList_GET_SIZE(xs)) {
                Py_DECREF(xs);
                goto error;
            }
            PyObject *line = PyList_GET_ITEM(xs, n - 1);
            PyObject_SetAttr(exc, &_Py_ID(text), line);
            Py_DECREF(xs);
        }
error:
        Py_DECREF(interactive_src);
        _PyErr_SetRaisedException(tstate, exc);
        return -1;
    }
    Py_DECREF(interactive_src);
    Py_DECREF(res);

    flush_io();
    return 0;
}

int
PyRun_InteractiveOneObject(FILE *fp, PyObject *filename, PyCompilerFlags *flags)
{
    int res;

    res = PyRun_InteractiveOneObjectEx(fp, filename, flags);
    if (res == -1) {
        PyErr_Print();
        flush_io();
    }
    return res;
}

int
PyRun_InteractiveOneFlags(FILE *fp, const char *filename_str, PyCompilerFlags *flags)
{
    PyObject *filename;
    int res;

    filename = PyUnicode_DecodeFSDefault(filename_str);
    if (filename == NULL) {
        PyErr_Print();
        return -1;
    }
    res = PyRun_InteractiveOneObject(fp, filename, flags);
    Py_DECREF(filename);
    return res;
}


/* Check whether a file maybe a pyc file: Look at the extension,
   the file type, and, if we may close it, at the first few bytes. */

static int
maybe_pyc_file(FILE *fp, PyObject *filename, int closeit)
{
    PyObject *ext = PyUnicode_FromString(".pyc");
    if (ext == NULL) {
        return -1;
    }
    Py_ssize_t endswith = PyUnicode_Tailmatch(filename, ext, 0, PY_SSIZE_T_MAX, +1);
    Py_DECREF(ext);
    if (endswith) {
        return 1;
    }

    /* Only look into the file if we are allowed to close it, since
       it then should also be seekable. */
    if (!closeit) {
        return 0;
    }

    /* Read only two bytes of the magic. If the file was opened in
       text mode, the bytes 3 and 4 of the magic (\r\n) might not
       be read as they are on disk. */
    unsigned int halfmagic = PyImport_GetMagicNumber() & 0xFFFF;
    unsigned char buf[2];
    /* Mess:  In case of -x, the stream is NOT at its start now,
       and ungetc() was used to push back the first newline,
       which makes the current stream position formally undefined,
       and a x-platform nightmare.
       Unfortunately, we have no direct way to know whether -x
       was specified.  So we use a terrible hack:  if the current
       stream position is not 0, we assume -x was specified, and
       give up.  Bug 132850 on SourceForge spells out the
       hopelessness of trying anything else (fseek and ftell
       don't work predictably x-platform for text-mode files).
    */
    int ispyc = 0;
    if (ftell(fp) == 0) {
        if (fread(buf, 1, 2, fp) == 2 &&
            ((unsigned int)buf[1]<<8 | buf[0]) == halfmagic)
            ispyc = 1;
        rewind(fp);
    }
    return ispyc;
}


static int
set_main_loader(PyObject *d, PyObject *filename, const char *loader_name)
{
    PyInterpreterState *interp = _PyInterpreterState_GET();
    PyObject *loader_type = _PyImport_GetImportlibExternalLoader(interp,
                                                                 loader_name);
    if (loader_type == NULL) {
        return -1;
    }

    PyObject *loader = PyObject_CallFunction(loader_type,
                                             "sO", "__main__", filename);
    Py_DECREF(loader_type);
    if (loader == NULL) {
        return -1;
    }

    if (PyDict_SetItemString(d, "__loader__", loader) < 0) {
        Py_DECREF(loader);
        return -1;
    }
    Py_DECREF(loader);
    return 0;
}


int
_PyRun_SimpleFileObject(FILE *fp, PyObject *filename, int closeit,
                        PyCompilerFlags *flags)
{
    int ret = -1;

    PyObject *main_module = PyImport_AddModuleRef("__main__");
    if (main_module == NULL)
        return -1;
    PyObject *dict = PyModule_GetDict(main_module);  // borrowed ref

    int set_file_name = 0;
    int has_file = PyDict_ContainsString(dict, "__file__");
    if (has_file < 0) {
        goto done;
    }
    if (!has_file) {
        if (PyDict_SetItemString(dict, "__file__", filename) < 0) {
            goto done;
        }
        if (PyDict_SetItemString(dict, "__cached__", Py_None) < 0) {
            goto done;
        }
        set_file_name = 1;
    }

    int pyc = maybe_pyc_file(fp, filename, closeit);
    if (pyc < 0) {
        goto done;
    }

    PyObject *v;
    if (pyc) {
        FILE *pyc_fp;
        /* Try to run a pyc file. First, re-open in binary */
        if (closeit) {
            fclose(fp);
        }

        pyc_fp = Py_fopen(filename, "rb");
        if (pyc_fp == NULL) {
            fprintf(stderr, "python: Can't reopen .pyc file\n");
            goto done;
        }

        if (set_main_loader(dict, filename, "SourcelessFileLoader") < 0) {
            fprintf(stderr, "python: failed to set __main__.__loader__\n");
            ret = -1;
            fclose(pyc_fp);
            goto done;
        }
        v = run_pyc_file(pyc_fp, dict, dict, flags);
    } else {
        /* When running from stdin, leave __main__.__loader__ alone */
        if ((!PyUnicode_Check(filename) || !PyUnicode_EqualToUTF8(filename, "<stdin>")) &&
            set_main_loader(dict, filename, "SourceFileLoader") < 0) {
            fprintf(stderr, "python: failed to set __main__.__loader__\n");
            ret = -1;
            goto done;
        }
        v = pyrun_file(fp, filename, Py_file_input, dict, dict,
                       closeit, flags);
    }
    flush_io();
    if (v == NULL) {
        Py_CLEAR(main_module);
        PyErr_Print();
        goto done;
    }
    Py_DECREF(v);
    ret = 0;

  done:
    if (set_file_name) {
        if (PyDict_PopString(dict, "__file__", NULL) < 0) {
            PyErr_Print();
        }
        if (PyDict_PopString(dict, "__cached__", NULL) < 0) {
            PyErr_Print();
        }
    }
    Py_XDECREF(main_module);
    return ret;
}


int
PyRun_SimpleFileExFlags(FILE *fp, const char *filename, int closeit,
                        PyCompilerFlags *flags)
{
    PyObject *filename_obj = PyUnicode_DecodeFSDefault(filename);
    if (filename_obj == NULL) {
        return -1;
    }
    int res = _PyRun_SimpleFileObject(fp, filename_obj, closeit, flags);
    Py_DECREF(filename_obj);
    return res;
}


int
_PyRun_SimpleStringFlagsWithName(const char *command, const char* name, PyCompilerFlags *flags) {
    PyObject *main_module = PyImport_AddModuleRef("__main__");
    if (main_module == NULL) {
        return -1;
    }
    PyObject *dict = PyModule_GetDict(main_module);  // borrowed ref

    PyObject *res = NULL;
    if (name == NULL) {
        res = PyRun_StringFlags(command, Py_file_input, dict, dict, flags);
    } else {
        PyObject* the_name = PyUnicode_FromString(name);
        if (!the_name) {
            PyErr_Print();
            return -1;
        }
        res = _PyRun_StringFlagsWithName(command, the_name, Py_file_input, dict, dict, flags, 0);
        Py_DECREF(the_name);
    }
    Py_DECREF(main_module);
    if (res == NULL) {
        PyErr_Print();
        return -1;
    }

    Py_DECREF(res);
    return 0;
}

int
PyRun_SimpleStringFlags(const char *command, PyCompilerFlags *flags)
{
    return _PyRun_SimpleStringFlagsWithName(command, NULL, flags);
}

static int
parse_exit_code(PyObject *code, int *exitcode_p)
{
    if (PyLong_Check(code)) {
        // gh-125842: Use a long long to avoid an overflow error when `long`
        // is 32-bit. We still truncate the result to an int.
        int exitcode = (int)PyLong_AsLongLong(code);
        if (exitcode == -1 && PyErr_Occurred()) {
            // On overflow or other error, clear the exception and use -1
            // as the exit code to match historical Python behavior.
            PyErr_Clear();
            *exitcode_p = -1;
            return 1;
        }
        *exitcode_p = exitcode;
        return 1;
    }
    else if (code == Py_None) {
        *exitcode_p = 0;
        return 1;
    }
    return 0;
}

int
_Py_HandleSystemExitAndKeyboardInterrupt(int *exitcode_p)
{
    if (PyErr_ExceptionMatches(PyExc_KeyboardInterrupt)) {
        _Py_atomic_store_int(&_PyRuntime.signals.unhandled_keyboard_interrupt, 1);
        return 0;
    }

    int inspect = _Py_GetConfig()->inspect;
    if (inspect) {
        /* Don't exit if -i flag was given. This flag is set to 0
         * when entering interactive mode for inspecting. */
        return 0;
    }

    if (!PyErr_ExceptionMatches(PyExc_SystemExit)) {
        return 0;
    }

    fflush(stdout);

    PyObject *exc = PyErr_GetRaisedException();
    assert(exc != NULL && PyExceptionInstance_Check(exc));

    PyObject *code = PyObject_GetAttr(exc, &_Py_ID(code));
    if (code == NULL) {
        // If the exception has no 'code' attribute, print the exception below
        PyErr_Clear();
    }
    else if (parse_exit_code(code, exitcode_p)) {
        Py_DECREF(code);
        Py_CLEAR(exc);
        return 1;
    }
    else {
        // If code is not an int or None, print it below
        Py_SETREF(exc, code);
    }

    PyObject *sys_stderr;
    if (PySys_GetOptionalAttr(&_Py_ID(stderr), &sys_stderr) < 0) {
        PyErr_Clear();
    }
    else if (sys_stderr != NULL && sys_stderr != Py_None) {
        if (PyFile_WriteObject(exc, sys_stderr, Py_PRINT_RAW) < 0) {
            PyErr_Clear();
        }
    }
    else {
        if (PyObject_Print(exc, stderr, Py_PRINT_RAW) < 0) {
            PyErr_Clear();
        }
        fflush(stderr);
    }
    PySys_WriteStderr("\n");
    Py_XDECREF(sys_stderr);
    Py_CLEAR(exc);
    *exitcode_p = 1;
    return 1;
}


static void
handle_system_exit(void)
{
    int exitcode;
    if (_Py_HandleSystemExitAndKeyboardInterrupt(&exitcode)) {
        Py_Exit(exitcode);
    }
}


static void
_PyErr_PrintEx(PyThreadState *tstate, int set_sys_last_vars)
{
    PyObject *typ = NULL, *tb = NULL, *hook = NULL;
    handle_system_exit();

    PyObject *exc = _PyErr_GetRaisedException(tstate);
    if (exc == NULL) {
        goto done;
    }
    assert(PyExceptionInstance_Check(exc));
    typ = Py_NewRef(Py_TYPE(exc));
    tb = PyException_GetTraceback(exc);
    if (tb == NULL) {
        tb = Py_NewRef(Py_None);
    }

    if (set_sys_last_vars) {
        if (_PySys_SetAttr(&_Py_ID(last_exc), exc) < 0) {
            _PyErr_Clear(tstate);
        }
        /* Legacy version: */
        if (_PySys_SetAttr(&_Py_ID(last_type), typ) < 0) {
            _PyErr_Clear(tstate);
        }
        if (_PySys_SetAttr(&_Py_ID(last_value), exc) < 0) {
            _PyErr_Clear(tstate);
        }
        if (_PySys_SetAttr(&_Py_ID(last_traceback), tb) < 0) {
            _PyErr_Clear(tstate);
        }
    }
    if (PySys_GetOptionalAttr(&_Py_ID(excepthook), &hook) < 0) {
        PyErr_Clear();
    }
    if (_PySys_Audit(tstate, "sys.excepthook", "OOOO", hook ? hook : Py_None,
                     typ, exc, tb) < 0) {
        if (PyErr_ExceptionMatches(PyExc_RuntimeError)) {
            PyErr_Clear();
            goto done;
        }
        PyErr_FormatUnraisable("Exception ignored in audit hook");
    }
    if (hook) {
        PyObject* args[3] = {typ, exc, tb};
        PyObject *result = PyObject_Vectorcall(hook, args, 3, NULL);
        if (result == NULL) {
            handle_system_exit();

            PyObject *exc2 = _PyErr_GetRaisedException(tstate);
            assert(exc2 && PyExceptionInstance_Check(exc2));
            fflush(stdout);
            PySys_WriteStderr("Error in sys.excepthook:\n");
            PyErr_DisplayException(exc2);
            PySys_WriteStderr("\nOriginal exception was:\n");
            PyErr_DisplayException(exc);
            Py_DECREF(exc2);
        }
        else {
            Py_DECREF(result);
        }
    }
    else {
        PySys_WriteStderr("sys.excepthook is missing\n");
        PyErr_DisplayException(exc);
    }

done:
    Py_XDECREF(hook);
    Py_XDECREF(typ);
    Py_XDECREF(exc);
    Py_XDECREF(tb);
}

void
_PyErr_Print(PyThreadState *tstate)
{
    _PyErr_PrintEx(tstate, 1);
}

void
PyErr_PrintEx(int set_sys_last_vars)
{
    PyThreadState *tstate = _PyThreadState_GET();
    _PyErr_PrintEx(tstate, set_sys_last_vars);
}

void
PyErr_Print(void)
{
    PyErr_PrintEx(1);
}

struct exception_print_context
{
    PyObject *file;
    PyObject *seen;            // Prevent cycles in recursion
};

static int
print_exception_invalid_type(struct exception_print_context *ctx,
                             PyObject *value)
{
    PyObject *f = ctx->file;
    const char *const msg = "TypeError: print_exception(): Exception expected "
                            "for value, ";
    if (PyFile_WriteString(msg, f) < 0) {
        return -1;
    }
    if (PyFile_WriteString(Py_TYPE(value)->tp_name, f) < 0) {
        return -1;
    }
    if (PyFile_WriteString(" found\n", f) < 0) {
        return -1;
    }
    return 0;
}

static int
print_exception_traceback(struct exception_print_context *ctx, PyObject *value)
{
    PyObject *f = ctx->file;
    int err = 0;

    PyObject *tb = PyException_GetTraceback(value);
    if (tb && tb != Py_None) {
        const char *header = EXCEPTION_TB_HEADER;
        err = _PyTraceBack_Print(tb, header, f);
    }
    Py_XDECREF(tb);
    return err;
}

static int
print_exception_file_and_line(struct exception_print_context *ctx,
                              PyObject **value_p)
{
    PyObject *f = ctx->file;

    PyObject *tmp;
    int res = PyObject_GetOptionalAttr(*value_p, &_Py_ID(print_file_and_line), &tmp);
    if (res <= 0) {
        if (res < 0) {
            PyErr_Clear();
        }
        return 0;
    }
    Py_DECREF(tmp);

    PyObject *filename = NULL;
    Py_ssize_t lineno = 0;
    PyObject* v = PyObject_GetAttr(*value_p, &_Py_ID(filename));
    if (!v) {
        return -1;
    }
    if (v == Py_None) {
        Py_DECREF(v);
        _Py_DECLARE_STR(anon_string, "<string>");
        filename = Py_NewRef(&_Py_STR(anon_string));
    }
    else {
        filename = v;
    }

    PyObject *line = PyUnicode_FromFormat("  File \"%S\", line %zd\n",
                                          filename, lineno);
    Py_DECREF(filename);
    if (line == NULL) {
        goto error;
    }
    if (PyFile_WriteObject(line, f, Py_PRINT_RAW) < 0) {
        goto error;
    }
    Py_CLEAR(line);

    assert(!PyErr_Occurred());
    return 0;

error:
    Py_XDECREF(line);
    return -1;
}

/* Prints the message line: module.qualname[: str(exc)] */
static int
print_exception_message(struct exception_print_context *ctx, PyObject *type,
                        PyObject *value)
{
    PyObject *f = ctx->file;

    if (PyErr_GivenExceptionMatches(value, PyExc_MemoryError)) {
        // The Python APIs in this function require allocating memory
        // for various objects. If we're out of memory, we can't do that,
        return -1;
    }

    assert(PyExceptionClass_Check(type));

    PyObject *modulename = PyObject_GetAttr(type, &_Py_ID(__module__));
    if (modulename == NULL || !PyUnicode_Check(modulename)) {
        Py_XDECREF(modulename);
        PyErr_Clear();
        if (PyFile_WriteString("<unknown>.", f) < 0) {
            return -1;
        }
    }
    else {
        if (!_PyUnicode_Equal(modulename, &_Py_ID(builtins)) &&
            !_PyUnicode_Equal(modulename, &_Py_ID(__main__)))
        {
            int res = PyFile_WriteObject(modulename, f, Py_PRINT_RAW);
            Py_DECREF(modulename);
            if (res < 0) {
                return -1;
            }
            if (PyFile_WriteString(".", f) < 0) {
                return -1;
            }
        }
        else {
            Py_DECREF(modulename);
        }
    }

    PyObject *qualname = PyType_GetQualName((PyTypeObject *)type);
    if (qualname == NULL || !PyUnicode_Check(qualname)) {
        Py_XDECREF(qualname);
        PyErr_Clear();
        if (PyFile_WriteString("<unknown>", f) < 0) {
            return -1;
        }
    }
    else {
        int res = PyFile_WriteObject(qualname, f, Py_PRINT_RAW);
        Py_DECREF(qualname);
        if (res < 0) {
            return -1;
        }
    }

    if (Py_IsNone(value)) {
        return 0;
    }

    PyObject *s = PyObject_Str(value);
    if (s == NULL) {
        PyErr_Clear();
        if (PyFile_WriteString(": <exception str() failed>", f) < 0) {
            return -1;
        }
    }
    else {
        /* only print colon if the str() of the
           object is not the empty string
        */
        if (!PyUnicode_Check(s) || PyUnicode_GetLength(s) != 0) {
            if (PyFile_WriteString(": ", f) < 0) {
                Py_DECREF(s);
                return -1;
            }
        }
        int res = PyFile_WriteObject(s, f, Py_PRINT_RAW);
        Py_DECREF(s);
        if (res < 0) {
            return -1;
        }
    }

    return 0;
}

static int
print_exception(struct exception_print_context *ctx, PyObject *value)
{
    PyObject *f = ctx->file;

    if (!PyExceptionInstance_Check(value)) {
        return print_exception_invalid_type(ctx, value);
    }

    Py_INCREF(value);
    fflush(stdout);

    if (print_exception_traceback(ctx, value) < 0) {
        goto error;
    }

    /* grab the type and notes now because value can change below */
    PyObject *type = (PyObject *) Py_TYPE(value);

    if (print_exception_file_and_line(ctx, &value) < 0) {
        goto error;
    }
    if (print_exception_message(ctx, type, value) < 0) {
        goto error;
    }
    if (PyFile_WriteString("\n", f) < 0) {
        goto error;
    }
    Py_DECREF(value);
    assert(!PyErr_Occurred());
    return 0;
error:
    Py_DECREF(value);
    return -1;
}

static const char cause_message[] =