cpython/Python/traceback.c

/* Traceback implementation */

#include "Python.h"

#include "code.h"
#include "frameobject.h"
#include "structmember.h"
#include "osdefs.h"
#include "traceback.h"

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

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 */
    0,                  /* 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 */
    0,                                          /* 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 = PyFrame_GetLineNumber(frame);
        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;
}

int
_Py_DisplaySourceLine(PyObject *f, const char *filename, int lineno, int indent)
{
    int err = 0;
    FILE *xfp = NULL;
    char linebuf[2000];
    int i;
    char namebuf[MAXPATHLEN+1];

    if (filename == NULL)
        return -1;
    /* This is needed by Emacs' compile command */
#define FMT "  File \"%.500s\", line %d, in %.500s\n"
    xfp = fopen(filename, "r" PY_STDIOTEXTMODE);
    if (xfp == NULL) {
        /* Search tail of filename in sys.path before giving up */
        PyObject *path;
        const char *tail = strrchr(filename, SEP);
        if (tail == NULL)
            tail = filename;
        else
            tail++;
        path = PySys_GetObject("path");
        if (path != NULL && PyList_Check(path)) {
            Py_ssize_t _npath = PyList_Size(path);
            int npath = Py_SAFE_DOWNCAST(_npath, Py_ssize_t, int);
            size_t taillen = strlen(tail);
            for (i = 0; i < npath; i++) {
                PyObject *v = PyList_GetItem(path, i);
                if (v == NULL) {
                    PyErr_Clear();
                    break;
                }
                if (PyString_Check(v)) {
                    size_t len;
                    len = PyString_GET_SIZE(v);
                    if (len + 1 + taillen >= MAXPATHLEN)
                        continue; /* Too long */
                    strcpy(namebuf, PyString_AsString(v));
                    if (strlen(namebuf) != len)
                        continue; /* v contains '\0' */
                    if (len > 0 && namebuf[len-1] != SEP)
                        namebuf[len++] = SEP;
                    strcpy(namebuf+len, tail);
                    xfp = fopen(namebuf, "r" PY_STDIOTEXTMODE);
                    if (xfp != NULL) {
                        break;
                    }
                }
            }
        }
    }

    if (xfp == NULL)
        return err;

    for (i = 0; i < lineno; i++) {
        char* pLastChar = &linebuf[sizeof(linebuf)-2];
        do {
            *pLastChar = '\0';
            if (Py_UniversalNewlineFgets(linebuf, sizeof linebuf, xfp, NULL) == NULL)
                break;
            /* fgets read *something*; if it didn't get as
               far as pLastChar, it must have found a newline
               or hit the end of the file;              if pLastChar is \n,
               it obviously found a newline; else we haven't
               yet seen a newline, so must continue */
        } while (*pLastChar != '\0' && *pLastChar != '\n');
    }
    if (i == lineno) {
        char buf[11];
        char *p = linebuf;
        while (*p == ' ' || *p == '\t' || *p == '\014')
            p++;

        /* 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;
        }

        if (err == 0)
            err = PyFile_WriteString(p, f);
        if (err == 0 && strchr(p, '\n') == NULL)
            err = PyFile_WriteString("\n", f);
    }
    fclose(xfp);
    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,
                PyString_AsString(
                    tb->tb_frame->f_code->co_filename),
                tb->tb_lineno,
                PyString_AsString(tb->tb_frame->f_code->co_name));
        }
        depth--;
        tb = tb->tb_next;
        if (err == 0)
            err = PyErr_CheckSignals();
    }
    return err;
}

int
PyTraceBack_Print(PyObject *v, PyObject *f)
{
    int err;
    PyObject *limitv;
    long limit = 1000;
    if (v == NULL)
        return 0;
    if (!PyTraceBack_Check(v)) {
        PyErr_BadInternalCall();
        return -1;
    }
    limitv = PySys_GetObject("tracebacklimit");
    if (limitv && PyInt_Check(limitv)) {
        limit = PyInt_AsLong(limitv);
        if (limit <= 0)
            return 0;
    }
    err = PyFile_WriteString("Traceback (most recent call last):\n", f);
    if (!err)
        err = tb_printinternal((PyTracebackObject *)v, f, limit);
    return err;
}