cpython/Python/traceback.c

/* Traceback implementation */

#include "Python.h"

#include "code.h"
#include "frameobject.h"
#include "structmember.h"
#include "osdefs.h"
#include "traceback.h"
#ifdef HAVE_FCNTL_H
#include <fcntl.h>
#endif

#define OFF(x) offsetof(PyTracebackObject, x)

/* Method from Parser/tokenizer.c */
extern char * PyTokenizer_FindEncoding(int);

static PyObject *
tb_dir(PyTracebackObject *self)
{
    return Py_BuildValue("[ssss]", "tb_frame", "tb_next",
                                   "tb_lasti", "tb_lineno");
}

static PyMethodDef tb_methods[] = {
   {"__dir__", (PyCFunction)tb_dir, METH_NOARGS},
   {NULL, NULL, 0, NULL},
};

static PyMemberDef tb_memberlist[] = {
	{"tb_next",	T_OBJECT,	OFF(tb_next),	READONLY},
	{"tb_frame",	T_OBJECT,	OFF(tb_frame),	READONLY},
	{"tb_lasti",	T_INT,		OFF(tb_lasti),	READONLY},
	{"tb_lineno",	T_INT,		OFF(tb_lineno),	READONLY},
	{NULL}	/* Sentinel */
};

static void
tb_dealloc(PyTracebackObject *tb)
{
	PyObject_GC_UnTrack(tb);
	Py_TRASHCAN_SAFE_BEGIN(tb)
	Py_XDECREF(tb->tb_next);
	Py_XDECREF(tb->tb_frame);
	PyObject_GC_Del(tb);
	Py_TRASHCAN_SAFE_END(tb)
}

static int
tb_traverse(PyTracebackObject *tb, visitproc visit, void *arg)
{
	Py_VISIT(tb->tb_next);
	Py_VISIT(tb->tb_frame);
	return 0;
}

static void
tb_clear(PyTracebackObject *tb)
{
	Py_CLEAR(tb->tb_next);
	Py_CLEAR(tb->tb_frame);
}

PyTypeObject PyTraceBack_Type = {
	PyVarObject_HEAD_INIT(&PyType_Type, 0)
	"traceback",
	sizeof(PyTracebackObject),
	0,
	(destructor)tb_dealloc, /*tp_dealloc*/
	0,		/*tp_print*/
	0,    /*tp_getattr*/
	0,		/*tp_setattr*/
	0,		/*tp_compare*/
	0,		/*tp_repr*/
	0,		/*tp_as_number*/
	0,		/*tp_as_sequence*/
	0,		/*tp_as_mapping*/
	0,		/* tp_hash */
	0,		/* tp_call */
	0,		/* tp_str */
	PyObject_GenericGetAttr,		/* tp_getattro */
	0,		/* tp_setattro */
	0,					/* tp_as_buffer */
	Py_TPFLAGS_DEFAULT | Py_TPFLAGS_HAVE_GC,/* tp_flags */
	0,             				/* tp_doc */
 	(traverseproc)tb_traverse,		/* tp_traverse */
	(inquiry)tb_clear,			/* tp_clear */
	0,					/* tp_richcompare */
	0,					/* tp_weaklistoffset */
	0,					/* tp_iter */
	0,					/* tp_iternext */
	tb_methods,	/* tp_methods */
	tb_memberlist,	/* tp_members */
	0,					/* tp_getset */
	0,					/* tp_base */
	0,					/* tp_dict */
};

static PyTracebackObject *
newtracebackobject(PyTracebackObject *next, PyFrameObject *frame)
{
	PyTracebackObject *tb;
	if ((next != NULL && !PyTraceBack_Check(next)) ||
			frame == NULL || !PyFrame_Check(frame)) {
		PyErr_BadInternalCall();
		return NULL;
	}
	tb = PyObject_GC_New(PyTracebackObject, &PyTraceBack_Type);
	if (tb != NULL) {
		Py_XINCREF(next);
		tb->tb_next = next;
		Py_XINCREF(frame);
		tb->tb_frame = frame;
		tb->tb_lasti = frame->f_lasti;
		tb->tb_lineno = PyCode_Addr2Line(frame->f_code, 
						 frame->f_lasti);
		PyObject_GC_Track(tb);
	}
	return tb;
}

int
PyTraceBack_Here(PyFrameObject *frame)
{
	PyThreadState *tstate = PyThreadState_GET();
	PyTracebackObject *oldtb = (PyTracebackObject *) tstate->curexc_traceback;
	PyTracebackObject *tb = newtracebackobject(oldtb, frame);
	if (tb == NULL)
		return -1;
	tstate->curexc_traceback = (PyObject *)tb;
	Py_XDECREF(oldtb);
	return 0;
}

static int
_Py_FindSourceFile(const char* filename, char* namebuf, size_t namelen, int open_flags)
{
	int i;
	int fd = -1;
	PyObject *v;
	Py_ssize_t _npath;
	int npath;
	size_t taillen;
	PyObject *syspath;
	const char* path;
	const char* tail;
	Py_ssize_t len;

	/* Search tail of filename in sys.path before giving up */
	tail = strrchr(filename, SEP);
	if (tail == NULL)
		tail = filename;
	else
		tail++;
	taillen = strlen(tail);

	syspath = PySys_GetObject("path");
	if (syspath == NULL || !PyList_Check(syspath))
		return -1;
	_npath = PyList_Size(syspath);
	npath = Py_SAFE_DOWNCAST(_npath, Py_ssize_t, int);

	for (i = 0; i < npath; i++) {
		v = PyList_GetItem(syspath, i);
		if (v == NULL) {
			PyErr_Clear();
			break;
		}
		if (!PyUnicode_Check(v))
			continue;
		path = _PyUnicode_AsStringAndSize(v, &len);
		if (len + 1 + (Py_ssize_t)taillen >= (Py_ssize_t)namelen - 1)
			continue; /* Too long */
		strcpy(namebuf, path);
		if (strlen(namebuf) != len)
			continue; /* v contains '\0' */
		if (len > 0 && namebuf[len-1] != SEP)
			namebuf[len++] = SEP;
		strcpy(namebuf+len, tail);
		Py_BEGIN_ALLOW_THREADS
		fd = open(namebuf, open_flags);
		Py_END_ALLOW_THREADS
		if (0 <= fd) {
			return fd;
		}
	}
	return -1;
}

int
_Py_DisplaySourceLine(PyObject *f, const char *filename, int lineno, int indent)
{
	int err = 0;
	int fd;
	int i;
	char *found_encoding;
	char *encoding;
	PyObject *fob = NULL;
	PyObject *lineobj = NULL;
#ifdef O_BINARY
	const int open_flags = O_RDONLY | O_BINARY;   /* necessary for Windows */
#else
	const int open_flags = O_RDONLY;
#endif
	char buf[MAXPATHLEN+1];
	Py_UNICODE *u, *p;
	Py_ssize_t len;

	/* open the file */
	if (filename == NULL)
		return 0;
	Py_BEGIN_ALLOW_THREADS
	fd = open(filename, open_flags);
	Py_END_ALLOW_THREADS
	if (fd < 0) {
		fd = _Py_FindSourceFile(filename, buf, sizeof(buf), open_flags);
		if (fd < 0)
			return 0;
		filename = buf;
	}

	/* use the right encoding to decode the file as unicode */
	found_encoding = PyTokenizer_FindEncoding(fd);
	encoding = (found_encoding != NULL) ? found_encoding :
		(char*)PyUnicode_GetDefaultEncoding();
	lseek(fd, 0, 0); /* Reset position */
	fob = PyFile_FromFd(fd, (char*)filename, "r", -1, (char*)encoding,
		NULL, NULL, 1);
	PyMem_FREE(found_encoding);
	if (fob == NULL) {
		PyErr_Clear();
		close(fd);
		return 0;
	}

	/* get the line number lineno */
	for (i = 0; i < lineno; i++) {
		Py_XDECREF(lineobj);
		lineobj = PyFile_GetLine(fob, -1);
		if (!lineobj) {
			err = -1;
			break;
		}
	}
	Py_DECREF(fob);
	if (!lineobj || !PyUnicode_Check(lineobj)) {
		Py_XDECREF(lineobj);
		return err;
	}

	/* remove the indentation of the line */
	u = PyUnicode_AS_UNICODE(lineobj);
	len = PyUnicode_GET_SIZE(lineobj);
	for (p=u; *p == ' ' || *p == '\t' || *p == '\014'; p++)
		len--;
	if (u != p) {
		PyObject *truncated;
		truncated = PyUnicode_FromUnicode(p, len);
		if (truncated) {
			Py_DECREF(lineobj);
			lineobj = truncated;
		} else {
			PyErr_Clear();
		}
	}

	/* Write some spaces before the line */
	strcpy(buf, "          ");
	assert (strlen(buf) == 10);
	while (indent > 0) {
		if(indent < 10)
			buf[indent] = '\0';
		err = PyFile_WriteString(buf, f);
		if (err != 0)
			break;
		indent -= 10;
	}

	/* finally display the line */
	if (err == 0)
		err = PyFile_WriteObject(lineobj, f, Py_PRINT_RAW);
	Py_DECREF(lineobj);
	if  (err == 0)
		err = PyFile_WriteString("\n", f);
	return err;
}

static int
tb_displayline(PyObject *f, const char *filename, int lineno, const char *name)
{
	int err = 0;
        char linebuf[2000];

	if (filename == NULL || name == NULL)
		return -1;
	/* This is needed by Emacs' compile command */
#define FMT "  File \"%.500s\", line %d, in %.500s\n"
	PyOS_snprintf(linebuf, sizeof(linebuf), FMT, filename, lineno, name);
	err = PyFile_WriteString(linebuf, f);
	if (err != 0)
		return err;
        return _Py_DisplaySourceLine(f, filename, lineno, 4);
}

static int
tb_printinternal(PyTracebackObject *tb, PyObject *f, long limit)
{
	int err = 0;
	long depth = 0;
	PyTracebackObject *tb1 = tb;
	while (tb1 != NULL) {
		depth++;
		tb1 = tb1->tb_next;
	}
	while (tb != NULL && err == 0) {
		if (depth <= limit) {
			err = tb_displayline(f,
			    _PyUnicode_AsString(
				    tb->tb_frame->f_code->co_filename),
			    tb->tb_lineno,
			    _PyUnicode_AsString(tb->tb_frame->f_code->co_name));
		}
		depth--;
		tb = tb->tb_next;
		if (err == 0)
			err = PyErr_CheckSignals();
	}
	return err;
}

#define PyTraceBack_LIMIT 1000

int
PyTraceBack_Print(PyObject *v, PyObject *f)
{
	int err;
	PyObject *limitv;
	long limit = PyTraceBack_LIMIT;

	if (v == NULL)
		return 0;
	if (!PyTraceBack_Check(v)) {
		PyErr_BadInternalCall();
		return -1;
	}
	limitv = PySys_GetObject("tracebacklimit");
	if (limitv) {
		PyObject *exc_type, *exc_value, *exc_tb;

		PyErr_Fetch(&exc_type, &exc_value, &exc_tb);
		limit = PyLong_AsLong(limitv);
		if (limit == -1 && PyErr_Occurred()) {
			if (PyErr_ExceptionMatches(PyExc_OverflowError)) {
				limit = PyTraceBack_LIMIT;
			}
			else {
				Py_XDECREF(exc_type);
				Py_XDECREF(exc_value);
				Py_XDECREF(exc_tb);
				return 0;
			}
		}
		else if (limit <= 0) {
			limit = PyTraceBack_LIMIT;
		}
		PyErr_Restore(exc_type, exc_value, exc_tb);
	}
	err = PyFile_WriteString("Traceback (most recent call last):\n", f);
	if (!err)
		err = tb_printinternal((PyTracebackObject *)v, f, limit);
	return err;
}