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gh-101659: Avoid Allocation for Shared Exceptions in the _xxsubinterpreters Module #102659

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merged 1 commit into from
Mar 13, 2023
Merged

gh-101659: Avoid Allocation for Shared Exceptions in the _xxsubinterpreters Module #102659

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123 changes: 49 additions & 74 deletions Modules/_xxsubinterpretersmodule.c
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Original file line number Diff line number Diff line change
Expand Up @@ -15,14 +15,14 @@
#define MODULE_NAME "_xxsubinterpreters"


static char *
static const char *
_copy_raw_string(PyObject *strobj)
{
const char *str = PyUnicode_AsUTF8(strobj);
if (str == NULL) {
return NULL;
}
char *copied = PyMem_Malloc(strlen(str)+1);
char *copied = PyMem_RawMalloc(strlen(str)+1);
if (copied == NULL) {
PyErr_NoMemory();
return NULL;
Expand Down Expand Up @@ -128,7 +128,7 @@ clear_module_state(module_state *state)
/* data-sharing-specific code ***********************************************/

struct _sharednsitem {
char *name;
const char *name;
_PyCrossInterpreterData data;
};

Expand All @@ -152,7 +152,7 @@ static void
_sharednsitem_clear(struct _sharednsitem *item)
{
if (item->name != NULL) {
PyMem_Free(item->name);
PyMem_RawFree((void *)item->name);
item->name = NULL;
}
(void)_release_xid_data(&item->data, 1);
Expand Down Expand Up @@ -258,96 +258,74 @@ _sharedns_apply(_sharedns *shared, PyObject *ns)
// of the exception in the calling interpreter.

typedef struct _sharedexception {
char *name;
char *msg;
const char *name;
const char *msg;
} _sharedexception;

static _sharedexception *
_sharedexception_new(void)
{
_sharedexception *err = PyMem_NEW(_sharedexception, 1);
if (err == NULL) {
PyErr_NoMemory();
return NULL;
}
err->name = NULL;
err->msg = NULL;
return err;
}
static const struct _sharedexception no_exception = {
.name = NULL,
.msg = NULL,
};

static void
_sharedexception_clear(_sharedexception *exc)
{
if (exc->name != NULL) {
PyMem_Free(exc->name);
PyMem_RawFree((void *)exc->name);
}
if (exc->msg != NULL) {
PyMem_Free(exc->msg);
PyMem_RawFree((void *)exc->msg);
}
}

static void
_sharedexception_free(_sharedexception *exc)
{
_sharedexception_clear(exc);
PyMem_Free(exc);
}

static _sharedexception *
_sharedexception_bind(PyObject *exc)
static const char *
_sharedexception_bind(PyObject *exc, _sharedexception *sharedexc)
{
assert(exc != NULL);
char *failure = NULL;

_sharedexception *err = _sharedexception_new();
if (err == NULL) {
goto finally;
}
const char *failure = NULL;

PyObject *name = PyUnicode_FromFormat("%S", Py_TYPE(exc));
if (name == NULL) {
PyObject *nameobj = PyUnicode_FromFormat("%S", Py_TYPE(exc));
if (nameobj == NULL) {
failure = "unable to format exception type name";
goto finally;
goto error;
}
err->name = _copy_raw_string(name);
Py_DECREF(name);
if (err->name == NULL) {
sharedexc->name = _copy_raw_string(nameobj);
Py_DECREF(nameobj);
if (sharedexc->name == NULL) {
if (PyErr_ExceptionMatches(PyExc_MemoryError)) {
failure = "out of memory copying exception type name";
} else {
failure = "unable to encode and copy exception type name";
}
goto finally;
goto error;
}

if (exc != NULL) {
PyObject *msg = PyUnicode_FromFormat("%S", exc);
if (msg == NULL) {
PyObject *msgobj = PyUnicode_FromFormat("%S", exc);
if (msgobj == NULL) {
failure = "unable to format exception message";
goto finally;
goto error;
}
err->msg = _copy_raw_string(msg);
Py_DECREF(msg);
if (err->msg == NULL) {
sharedexc->msg = _copy_raw_string(msgobj);
Py_DECREF(msgobj);
if (sharedexc->msg == NULL) {
if (PyErr_ExceptionMatches(PyExc_MemoryError)) {
failure = "out of memory copying exception message";
} else {
failure = "unable to encode and copy exception message";
}
goto finally;
goto error;
}
}

finally:
if (failure != NULL) {
PyErr_Clear();
if (err->name != NULL) {
PyMem_Free(err->name);
err->name = NULL;
}
err->msg = failure;
}
return err;
return NULL;

error:
assert(failure != NULL);
PyErr_Clear();
_sharedexception_clear(sharedexc);
*sharedexc = no_exception;
return failure;
}

static void
Expand Down Expand Up @@ -430,7 +408,7 @@ _ensure_not_running(PyInterpreterState *interp)

static int
_run_script(PyInterpreterState *interp, const char *codestr,
_sharedns *shared, _sharedexception **exc)
_sharedns *shared, _sharedexception *sharedexc)
{
PyObject *excval = NULL;
PyObject *main_mod = _PyInterpreterState_GetMainModule(interp);
Expand Down Expand Up @@ -462,22 +440,20 @@ _run_script(PyInterpreterState *interp, const char *codestr,
Py_DECREF(result); // We throw away the result.
}

*exc = NULL;
*sharedexc = no_exception;
return 0;

error:
excval = PyErr_GetRaisedException();
_sharedexception *sharedexc = _sharedexception_bind(excval);
Py_XDECREF(excval);
if (sharedexc == NULL) {
fprintf(stderr, "RunFailedError: script raised an uncaught exception");
const char *failure = _sharedexception_bind(excval, sharedexc);
if (failure != NULL) {
fprintf(stderr,
"RunFailedError: script raised an uncaught exception (%s)",
failure);
PyErr_Clear();
sharedexc = NULL;
}
else {
assert(!PyErr_Occurred());
}
*exc = sharedexc;
Py_XDECREF(excval);
assert(!PyErr_Occurred());
return -1;
}

Expand Down Expand Up @@ -505,7 +481,7 @@ _run_script_in_interpreter(PyObject *mod, PyInterpreterState *interp,
}

// Run the script.
_sharedexception *exc = NULL;
_sharedexception exc;
int result = _run_script(interp, codestr, shared, &exc);

// Switch back.
Expand All @@ -514,10 +490,9 @@ _run_script_in_interpreter(PyObject *mod, PyInterpreterState *interp,
}

// Propagate any exception out to the caller.
if (exc != NULL) {
if (exc.name != NULL) {
assert(state != NULL);
_sharedexception_apply(exc, state->RunFailedError);
_sharedexception_free(exc);
_sharedexception_apply(&exc, state->RunFailedError);
}
else if (result != 0) {
// We were unable to allocate a shared exception.
Expand Down