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cpython/Parser/myreadline.c

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/* Readline interface for the tokenizer and [raw_]input() in bltinmodule.c.
By default, or when stdin is not a tty device, we have a super
simple my_readline function using fgets.
Optionally, we can use the GNU readline library.
my_readline() has a different return value from GNU readline():
- NULL if an interrupt occurred or if an error occurred
- a malloc'ed empty string if EOF was read
- a malloc'ed string ending in \n normally
*/
#include "Python.h"
#include "pycore_fileutils.h" // _Py_BEGIN_SUPPRESS_IPH
#include "pycore_pystate.h" // _PyThreadState_GET()
#ifdef MS_WINDOWS
# ifndef WIN32_LEAN_AND_MEAN
# define WIN32_LEAN_AND_MEAN
# endif
# include "windows.h"
#endif /* MS_WINDOWS */
#ifdef HAVE_UNISTD_H
# include <unistd.h> // isatty()
#endif
// Export the symbol since it's used by the readline shared extension
PyAPI_DATA(PyThreadState*) _PyOS_ReadlineTState;
PyThreadState *_PyOS_ReadlineTState = NULL;
static PyMutex _PyOS_ReadlineLock;
int (*PyOS_InputHook)(void) = NULL;
/* This function restarts a fgets() after an EINTR error occurred
except if _PyOS_InterruptOccurred() returns true. */
static int
my_fgets(PyThreadState* tstate, char *buf, int len, FILE *fp)
{
#ifdef MS_WINDOWS
HANDLE handle;
_Py_BEGIN_SUPPRESS_IPH
handle = (HANDLE)_get_osfhandle(fileno(fp));
_Py_END_SUPPRESS_IPH
/* bpo-40826: fgets(fp) does crash if fileno(fp) is closed */
if (handle == INVALID_HANDLE_VALUE) {
return -1; /* EOF */
}
#endif
while (1) {
if (PyOS_InputHook != NULL &&
// GH-104668: See PyOS_ReadlineFunctionPointer's comment below...
_Py_IsMainInterpreter(tstate->interp))
{
(void)(PyOS_InputHook)();
}
errno = 0;
clearerr(fp);
char *p = fgets(buf, len, fp);
if (p != NULL) {
return 0; /* No error */
}
int err = errno;
#ifdef MS_WINDOWS
/* Ctrl-C anywhere on the line or Ctrl-Z if the only character
on a line will set ERROR_OPERATION_ABORTED. Under normal
circumstances Ctrl-C will also have caused the SIGINT handler
to fire which will have set the event object returned by
_PyOS_SigintEvent. This signal fires in another thread and
is not guaranteed to have occurred before this point in the
code.
Therefore: check whether the event is set with a small timeout.
If it is, assume this is a Ctrl-C and reset the event. If it
isn't set assume that this is a Ctrl-Z on its own and drop
through to check for EOF.
*/
if (GetLastError()==ERROR_OPERATION_ABORTED) {
HANDLE hInterruptEvent = _PyOS_SigintEvent();
switch (WaitForSingleObjectEx(hInterruptEvent, 10, FALSE)) {
case WAIT_OBJECT_0:
ResetEvent(hInterruptEvent);
return 1; /* Interrupt */
case WAIT_FAILED:
return -2; /* Error */
}
}
#endif /* MS_WINDOWS */
if (feof(fp)) {
clearerr(fp);
return -1; /* EOF */
}
#ifdef EINTR
if (err == EINTR) {
PyEval_RestoreThread(tstate);
int s = PyErr_CheckSignals();
PyEval_SaveThread();
if (s < 0) {
return 1;
}
/* try again */
continue;
}
#endif
if (_PyOS_InterruptOccurred(tstate)) {
return 1; /* Interrupt */
}
return -2; /* Error */
}
/* NOTREACHED */
}
#ifdef HAVE_WINDOWS_CONSOLE_IO
/* Readline implementation using ReadConsoleW */
extern char _get_console_type(HANDLE handle);
char *
_PyOS_WindowsConsoleReadline(PyThreadState *tstate, HANDLE hStdIn)
{
static wchar_t wbuf_local[1024 * 16];
const DWORD chunk_size = 1024;
DWORD n_read, total_read, wbuflen, u8len;
wchar_t *wbuf;
char *buf = NULL;
int err = 0;
n_read = (DWORD)-1;
total_read = 0;
wbuf = wbuf_local;
wbuflen = sizeof(wbuf_local) / sizeof(wbuf_local[0]) - 1;
while (1) {
if (PyOS_InputHook != NULL &&
// GH-104668: See PyOS_ReadlineFunctionPointer's comment below...
_Py_IsMainInterpreter(tstate->interp))
{
(void)(PyOS_InputHook)();
}
if (!ReadConsoleW(hStdIn, &wbuf[total_read], wbuflen - total_read, &n_read, NULL)) {
err = GetLastError();
goto exit;
}
if (n_read == (DWORD)-1 && (err = GetLastError()) == ERROR_OPERATION_ABORTED) {
break;
}
if (n_read == 0) {
int s;
err = GetLastError();
if (err != ERROR_OPERATION_ABORTED)
goto exit;
err = 0;
HANDLE hInterruptEvent = _PyOS_SigintEvent();
if (WaitForSingleObjectEx(hInterruptEvent, 100, FALSE)
== WAIT_OBJECT_0) {
ResetEvent(hInterruptEvent);
PyEval_RestoreThread(tstate);
s = PyErr_CheckSignals();
PyEval_SaveThread();
if (s < 0) {
goto exit;
}
}
break;
}
total_read += n_read;
if (total_read == 0 || wbuf[total_read - 1] == L'\n') {
break;
}
wbuflen += chunk_size;
if (wbuf == wbuf_local) {
wbuf[total_read] = '\0';
wbuf = (wchar_t*)PyMem_RawMalloc(wbuflen * sizeof(wchar_t));
if (wbuf) {
wcscpy_s(wbuf, wbuflen, wbuf_local);
}
else {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
}
else {
wchar_t *tmp = PyMem_RawRealloc(wbuf, wbuflen * sizeof(wchar_t));
if (tmp == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
wbuf = tmp;
}
}
if (wbuf[0] == '\x1a') {
buf = PyMem_RawMalloc(1);
if (buf) {
buf[0] = '\0';
}
else {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
}
goto exit;
}
u8len = WideCharToMultiByte(CP_UTF8, 0,
wbuf, total_read,
NULL, 0,
NULL, NULL);
buf = PyMem_RawMalloc(u8len + 1);
if (buf == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
goto exit;
}
u8len = WideCharToMultiByte(CP_UTF8, 0,
wbuf, total_read,
buf, u8len,
NULL, NULL);
buf[u8len] = '\0';
exit:
if (wbuf != wbuf_local) {
PyMem_RawFree(wbuf);
}
if (err) {
PyEval_RestoreThread(tstate);
PyErr_SetFromWindowsErr(err);
PyEval_SaveThread();
}
return buf;
}
#endif /* HAVE_WINDOWS_CONSOLE_IO */
/* Readline implementation using fgets() */
char *
PyOS_StdioReadline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
{
size_t n;
char *p, *pr;
PyThreadState *tstate = _PyOS_ReadlineTState;
assert(tstate != NULL);
#ifdef HAVE_WINDOWS_CONSOLE_IO
const PyConfig *config = _PyInterpreterState_GetConfig(tstate->interp);
if (!config->legacy_windows_stdio && sys_stdin == stdin) {
HANDLE hStdIn, hStdErr;
hStdIn = _Py_get_osfhandle_noraise(fileno(sys_stdin));
hStdErr = _Py_get_osfhandle_noraise(fileno(stderr));
if (_get_console_type(hStdIn) == 'r') {
fflush(sys_stdout);
if (prompt) {
if (_get_console_type(hStdErr) == 'w') {
wchar_t *wbuf;
int wlen;
wlen = MultiByteToWideChar(CP_UTF8, 0, prompt, -1,
NULL, 0);
if (wlen) {
wbuf = PyMem_RawMalloc(wlen * sizeof(wchar_t));
if (wbuf == NULL) {
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
wlen = MultiByteToWideChar(CP_UTF8, 0, prompt, -1,
wbuf, wlen);
if (wlen) {
DWORD n;
fflush(stderr);
/* wlen includes null terminator, so subtract 1 */
WriteConsoleW(hStdErr, wbuf, wlen - 1, &n, NULL);
}
PyMem_RawFree(wbuf);
}
} else {
fprintf(stderr, "%s", prompt);
fflush(stderr);
}
}
clearerr(sys_stdin);
return _PyOS_WindowsConsoleReadline(tstate, hStdIn);
}
}
#endif
fflush(sys_stdout);
if (prompt) {
fprintf(stderr, "%s", prompt);
}
fflush(stderr);
n = 0;
p = NULL;
do {
size_t incr = (n > 0) ? n + 2 : 100;
if (incr > INT_MAX) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_SetString(PyExc_OverflowError, "input line too long");
PyEval_SaveThread();
return NULL;
}
pr = (char *)PyMem_RawRealloc(p, n + incr);
if (pr == NULL) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
p = pr;
int err = my_fgets(tstate, p + n, (int)incr, sys_stdin);
if (err == 1) {
// Interrupt
PyMem_RawFree(p);
return NULL;
} else if (err != 0) {
// EOF or error
p[n] = '\0';
break;
}
n += strlen(p + n);
} while (p[n-1] != '\n');
pr = (char *)PyMem_RawRealloc(p, n+1);
if (pr == NULL) {
PyMem_RawFree(p);
PyEval_RestoreThread(tstate);
PyErr_NoMemory();
PyEval_SaveThread();
return NULL;
}
return pr;
}
/* By initializing this function pointer, systems embedding Python can
override the readline function.
Note: Python expects in return a buffer allocated with PyMem_Malloc. */
char *(*PyOS_ReadlineFunctionPointer)(FILE *, FILE *, const char *) = NULL;
/* Interface used by file_tokenizer.c and bltinmodule.c */
char *
PyOS_Readline(FILE *sys_stdin, FILE *sys_stdout, const char *prompt)
{
char *rv, *res;
size_t len;
PyThreadState *tstate = _PyThreadState_GET();
if (_Py_atomic_load_ptr_relaxed(&_PyOS_ReadlineTState) == tstate) {
PyErr_SetString(PyExc_RuntimeError,
"can't re-enter readline");
return NULL;
}
// GH-123321: We need to acquire the lock before setting
// _PyOS_ReadlineTState, otherwise the variable may be nullified by a
// different thread.
Py_BEGIN_ALLOW_THREADS
PyMutex_Lock(&_PyOS_ReadlineLock);
_Py_atomic_store_ptr_relaxed(&_PyOS_ReadlineTState, tstate);
if (PyOS_ReadlineFunctionPointer == NULL) {
PyOS_ReadlineFunctionPointer = PyOS_StdioReadline;
}
/* This is needed to handle the unlikely case that the
* interpreter is in interactive mode *and* stdin/out are not
* a tty. This can happen, for example if python is run like
* this: python -i < test1.py
*/
if (!isatty(fileno(sys_stdin)) || !isatty(fileno(sys_stdout)) ||
// GH-104668: Don't call global callbacks like PyOS_InputHook or
// PyOS_ReadlineFunctionPointer from subinterpreters, since it seems
// like there's no good way for users (like readline and tkinter) to
// avoid using global state to manage them. Plus, we generally don't
// want to cause trouble for libraries that don't know/care about
// subinterpreter support. If libraries really need better APIs that
// work per-interpreter and have ways to access module state, we can
// certainly add them later (but for now we'll cross our fingers and
// hope that nobody actually cares):
!_Py_IsMainInterpreter(tstate->interp))
{
rv = PyOS_StdioReadline(sys_stdin, sys_stdout, prompt);
}
else {
rv = (*PyOS_ReadlineFunctionPointer)(sys_stdin, sys_stdout, prompt);
}
// gh-123321: Must set the variable and then release the lock before
// taking the GIL. Otherwise a deadlock or segfault may occur.
_Py_atomic_store_ptr_relaxed(&_PyOS_ReadlineTState, NULL);
PyMutex_Unlock(&_PyOS_ReadlineLock);
Py_END_ALLOW_THREADS
if (rv == NULL)
return NULL;
len = strlen(rv) + 1;
res = PyMem_Malloc(len);
if (res != NULL) {
memcpy(res, rv, len);
}
else {
PyErr_NoMemory();
}
PyMem_RawFree(rv);
return res;
}
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