Add python coverage module to third_party

third_party/pycoverage/coverage/tracer.c

Index: third_party/pycoverage/coverage/tracer.c
diff --git a/third_party/pycoverage/coverage/tracer.c b/third_party/pycoverage/coverage/tracer.c
new file mode 100644
index 0000000000000000000000000000000000000000..97dd113b8b3a814dbaa39d7fd0f7e1822f7a699f
--- /dev/null
+++ b/third_party/pycoverage/coverage/tracer.c
@@ -0,0 +1,730 @@
+/* C-based Tracer for Coverage. */
+
+#include "Python.h"
+#include "compile.h"        /* in 2.3, this wasn't part of Python.h */
+#include "eval.h"           /* or this. */
+#include "structmember.h"
+#include "frameobject.h"
+
+/* Compile-time debugging helpers */
+#undef WHAT_LOG         /* Define to log the WHAT params in the trace function. */
+#undef TRACE_LOG        /* Define to log our bookkeeping. */
+#undef COLLECT_STATS    /* Collect counters: stats are printed when tracer is stopped. */
+
+#if COLLECT_STATS
+#define STATS(x)        x
+#else
+#define STATS(x)
+#endif
+
+/* Py 2.x and 3.x compatibility */
+
+#ifndef Py_TYPE
+#define Py_TYPE(o)    (((PyObject*)(o))->ob_type)
+#endif
+
+#if PY_MAJOR_VERSION >= 3
+
+#define MyText_Type         PyUnicode_Type
+#define MyText_Check(o)     PyUnicode_Check(o)
+#define MyText_AS_BYTES(o)  PyUnicode_AsASCIIString(o)
+#define MyText_AS_STRING(o) PyBytes_AS_STRING(o)
+#define MyInt_FromLong(l)   PyLong_FromLong(l)
+
+#define MyType_HEAD_INIT    PyVarObject_HEAD_INIT(NULL, 0)
+
+#else
+
+#define MyText_Type         PyString_Type
+#define MyText_Check(o)     PyString_Check(o)
+#define MyText_AS_BYTES(o)  (Py_INCREF(o), o)
+#define MyText_AS_STRING(o) PyString_AS_STRING(o)
+#define MyInt_FromLong(l)   PyInt_FromLong(l)
+
+#define MyType_HEAD_INIT    PyObject_HEAD_INIT(NULL)  0,
+
+#endif /* Py3k */
+
+/* The values returned to indicate ok or error. */
+#define RET_OK      0
+#define RET_ERROR   -1
+
+/* An entry on the data stack.  For each call frame, we need to record the
+    dictionary to capture data, and the last line number executed in that
+    frame.
+*/
+typedef struct {
+    PyObject * file_data;  /* PyMem_Malloc'ed, a borrowed ref. */
+    int last_line;
+} DataStackEntry;
+
+/* The CTracer type. */
+
+typedef struct {
+    PyObject_HEAD
+
+    /* Python objects manipulated directly by the Collector class. */
+    PyObject * should_trace;
+    PyObject * warn;
+    PyObject * data;
+    PyObject * should_trace_cache;
+    PyObject * arcs;
+
+    /* Has the tracer been started? */
+    int started;
+    /* Are we tracing arcs, or just lines? */
+    int tracing_arcs;
+
+    /*
+        The data stack is a stack of dictionaries.  Each dictionary collects
+        data for a single source file.  The data stack parallels the call stack:
+        each call pushes the new frame's file data onto the data stack, and each
+        return pops file data off.
+
+        The file data is a dictionary whose form depends on the tracing options.
+        If tracing arcs, the keys are line number pairs.  If not tracing arcs,
+        the keys are line numbers.  In both cases, the value is irrelevant
+        (None).
+    */
+    /* The index of the last-used entry in data_stack. */
+    int depth;
+    /* The file data at each level, or NULL if not recording. */
+    DataStackEntry * data_stack;
+    int data_stack_alloc;       /* number of entries allocated at data_stack. */
+
+    /* The current file_data dictionary.  Borrowed. */
+    PyObject * cur_file_data;
+
+    /* The line number of the last line recorded, for tracing arcs.
+        -1 means there was no previous line, as when entering a code object.
+    */
+    int last_line;
+
+    /* The parent frame for the last exception event, to fix missing returns. */
+    PyFrameObject * last_exc_back;
+    int last_exc_firstlineno;
+
+#if COLLECT_STATS
+    struct {
+        unsigned int calls;
+        unsigned int lines;
+        unsigned int returns;
+        unsigned int exceptions;
+        unsigned int others;
+        unsigned int new_files;
+        unsigned int missed_returns;
+        unsigned int stack_reallocs;
+        unsigned int errors;
+    } stats;
+#endif /* COLLECT_STATS */
+} CTracer;
+
+#define STACK_DELTA    100
+
+static int
+CTracer_init(CTracer *self, PyObject *args_unused, PyObject *kwds_unused)
+{
+#if COLLECT_STATS
+    self->stats.calls = 0;
+    self->stats.lines = 0;
+    self->stats.returns = 0;
+    self->stats.exceptions = 0;
+    self->stats.others = 0;
+    self->stats.new_files = 0;
+    self->stats.missed_returns = 0;
+    self->stats.stack_reallocs = 0;
+    self->stats.errors = 0;
+#endif /* COLLECT_STATS */
+
+    self->should_trace = NULL;
+    self->warn = NULL;
+    self->data = NULL;
+    self->should_trace_cache = NULL;
+    self->arcs = NULL;
+
+    self->started = 0;
+    self->tracing_arcs = 0;
+
+    self->depth = -1;
+    self->data_stack = PyMem_Malloc(STACK_DELTA*sizeof(DataStackEntry));
+    if (self->data_stack == NULL) {
+        STATS( self->stats.errors++; )
+        PyErr_NoMemory();
+        return RET_ERROR;
+    }
+    self->data_stack_alloc = STACK_DELTA;
+
+    self->cur_file_data = NULL;
+    self->last_line = -1;
+
+    self->last_exc_back = NULL;
+
+    return RET_OK;
+}
+
+static void
+CTracer_dealloc(CTracer *self)
+{
+    if (self->started) {
+        PyEval_SetTrace(NULL, NULL);
+    }
+
+    Py_XDECREF(self->should_trace);
+    Py_XDECREF(self->warn);
+    Py_XDECREF(self->data);
+    Py_XDECREF(self->should_trace_cache);
+
+    PyMem_Free(self->data_stack);
+
+    Py_TYPE(self)->tp_free((PyObject*)self);
+}
+
+#if TRACE_LOG
+static const char *
+indent(int n)
+{
+    static const char * spaces =
+        "                                                                    "
+        "                                                                    "
+        "                                                                    "
+        "                                                                    "
+        ;
+    return spaces + strlen(spaces) - n*2;
+}
+
+static int logging = 0;
+/* Set these constants to be a file substring and line number to start logging. */
+static const char * start_file = "tests/views";
+static int start_line = 27;
+
+static void
+showlog(int depth, int lineno, PyObject * filename, const char * msg)
+{
+    if (logging) {
+        printf("%s%3d ", indent(depth), depth);
+        if (lineno) {
+            printf("%4d", lineno);
+        }
+        else {
+            printf("    ");
+        }
+        if (filename) {
+            PyObject *ascii = MyText_AS_BYTES(filename);
+            printf(" %s", MyText_AS_STRING(ascii));
+            Py_DECREF(ascii);
+        }
+        if (msg) {
+            printf(" %s", msg);
+        }
+        printf("\n");
+    }
+}
+
+#define SHOWLOG(a,b,c,d)    showlog(a,b,c,d)
+#else
+#define SHOWLOG(a,b,c,d)
+#endif /* TRACE_LOG */
+
+#if WHAT_LOG
+static const char * what_sym[] = {"CALL", "EXC ", "LINE", "RET "};
+#endif
+
+/* Record a pair of integers in self->cur_file_data. */
+static int
+CTracer_record_pair(CTracer *self, int l1, int l2)
+{
+    int ret = RET_OK;
+
+    PyObject * t = Py_BuildValue("(ii)", l1, l2);
+    if (t != NULL) {
+        if (PyDict_SetItem(self->cur_file_data, t, Py_None) < 0) {
+            STATS( self->stats.errors++; )
+            ret = RET_ERROR;
+        }
+        Py_DECREF(t);
+    }
+    else {
+        STATS( self->stats.errors++; )
+        ret = RET_ERROR;
+    }
+    return ret;
+}
+
+/*
+ * The Trace Function
+ */
+static int
+CTracer_trace(CTracer *self, PyFrameObject *frame, int what, PyObject *arg_unused)
+{
+    int ret = RET_OK;
+    PyObject * filename = NULL;
+    PyObject * tracename = NULL;
+    #if WHAT_LOG || TRACE_LOG
+    PyObject * ascii = NULL;
+    #endif
+
+    #if WHAT_LOG
+    if (what <= sizeof(what_sym)/sizeof(const char *)) {
+        ascii = MyText_AS_BYTES(frame->f_code->co_filename);
+        printf("trace: %s @ %s %d\n", what_sym[what], MyText_AS_STRING(ascii), frame->f_lineno);
+        Py_DECREF(ascii);
+    }
+    #endif
+
+    #if TRACE_LOG
+    ascii = MyText_AS_BYTES(frame->f_code->co_filename);
+    if (strstr(MyText_AS_STRING(ascii), start_file) && frame->f_lineno == start_line) {
+        logging = 1;
+    }
+    Py_DECREF(ascii);
+    #endif
+
+    /* See below for details on missing-return detection. */
+    if (self->last_exc_back) {
+        if (frame == self->last_exc_back) {
+            /* Looks like someone forgot to send a return event. We'll clear
+               the exception state and do the RETURN code here.  Notice that the
+               frame we have in hand here is not the correct frame for the RETURN,
+               that frame is gone.  Our handling for RETURN doesn't need the
+               actual frame, but we do log it, so that will look a little off if
+               you're looking at the detailed log.
+
+               If someday we need to examine the frame when doing RETURN, then
+               we'll need to keep more of the missed frame's state.
+            */
+            STATS( self->stats.missed_returns++; )
+            if (self->depth >= 0) {
+                if (self->tracing_arcs && self->cur_file_data) {
+                    if (CTracer_record_pair(self, self->last_line, -self->last_exc_firstlineno) < 0) {
+                        return RET_ERROR;
+                    }
+                }
+                SHOWLOG(self->depth, frame->f_lineno, frame->f_code->co_filename, "missedreturn");
+                self->cur_file_data = self->data_stack[self->depth].file_data;
+                self->last_line = self->data_stack[self->depth].last_line;
+                self->depth--;
+            }
+        }
+        self->last_exc_back = NULL;
+    }
+
+
+    switch (what) {
+    case PyTrace_CALL:      /* 0 */
+        STATS( self->stats.calls++; )
+        /* Grow the stack. */
+        self->depth++;
+        if (self->depth >= self->data_stack_alloc) {
+            STATS( self->stats.stack_reallocs++; )
+            /* We've outgrown our data_stack array: make it bigger. */
+            int bigger = self->data_stack_alloc + STACK_DELTA;
+            DataStackEntry * bigger_data_stack = PyMem_Realloc(self->data_stack, bigger * sizeof(DataStackEntry));
+            if (bigger_data_stack == NULL) {
+                STATS( self->stats.errors++; )
+                PyErr_NoMemory();
+                self->depth--;
+                return RET_ERROR;
+            }
+            self->data_stack = bigger_data_stack;
+            self->data_stack_alloc = bigger;
+        }
+
+        /* Push the current state on the stack. */
+        self->data_stack[self->depth].file_data = self->cur_file_data;
+        self->data_stack[self->depth].last_line = self->last_line;
+
+        /* Check if we should trace this line. */
+        filename = frame->f_code->co_filename;
+        tracename = PyDict_GetItem(self->should_trace_cache, filename);
+        if (tracename == NULL) {
+            STATS( self->stats.new_files++; )
+            /* We've never considered this file before. */
+            /* Ask should_trace about it. */
+            PyObject * args = Py_BuildValue("(OO)", filename, frame);
+            tracename = PyObject_Call(self->should_trace, args, NULL);
+            Py_DECREF(args);
+            if (tracename == NULL) {
+                /* An error occurred inside should_trace. */
+                STATS( self->stats.errors++; )
+                return RET_ERROR;
+            }
+            if (PyDict_SetItem(self->should_trace_cache, filename, tracename) < 0) {
+                STATS( self->stats.errors++; )
+                return RET_ERROR;
+            }
+        }
+        else {
+            Py_INCREF(tracename);
+        }
+
+        /* If tracename is a string, then we're supposed to trace. */
+        if (MyText_Check(tracename)) {
+            PyObject * file_data = PyDict_GetItem(self->data, tracename);
+            if (file_data == NULL) {
+                file_data = PyDict_New();
+                if (file_data == NULL) {
+                    STATS( self->stats.errors++; )
+                    return RET_ERROR;
+                }
+                ret = PyDict_SetItem(self->data, tracename, file_data);
+                Py_DECREF(file_data);
+                if (ret < 0) {
+                    STATS( self->stats.errors++; )
+                    return RET_ERROR;
+                }
+            }
+            self->cur_file_data = file_data;
+            /* Make the frame right in case settrace(gettrace()) happens. */
+            Py_INCREF(self);
+            frame->f_trace = (PyObject*)self;
+            SHOWLOG(self->depth, frame->f_lineno, filename, "traced");
+        }
+        else {
+            self->cur_file_data = NULL;
+            SHOWLOG(self->depth, frame->f_lineno, filename, "skipped");
+        }
+
+        Py_DECREF(tracename);
+
+        self->last_line = -1;
+        break;
+
+    case PyTrace_RETURN:    /* 3 */
+        STATS( self->stats.returns++; )
+        /* A near-copy of this code is above in the missing-return handler. */
+        if (self->depth >= 0) {
+            if (self->tracing_arcs && self->cur_file_data) {
+                int first = frame->f_code->co_firstlineno;
+                if (CTracer_record_pair(self, self->last_line, -first) < 0) {
+                    return RET_ERROR;
+                }
+            }
+
+            SHOWLOG(self->depth, frame->f_lineno, frame->f_code->co_filename, "return");
+            self->cur_file_data = self->data_stack[self->depth].file_data;
+            self->last_line = self->data_stack[self->depth].last_line;
+            self->depth--;
+        }
+        break;
+
+    case PyTrace_LINE:      /* 2 */
+        STATS( self->stats.lines++; )
+        if (self->depth >= 0) {
+            SHOWLOG(self->depth, frame->f_lineno, frame->f_code->co_filename, "line");
+            if (self->cur_file_data) {
+                /* We're tracing in this frame: record something. */
+                if (self->tracing_arcs) {
+                    /* Tracing arcs: key is (last_line,this_line). */
+                    if (CTracer_record_pair(self, self->last_line, frame->f_lineno) < 0) {
+                        return RET_ERROR;
+                    }
+                }
+                else {
+                    /* Tracing lines: key is simply this_line. */
+                    PyObject * this_line = MyInt_FromLong(frame->f_lineno);
+                    if (this_line == NULL) {
+                        STATS( self->stats.errors++; )
+                        return RET_ERROR;
+                    }
+                    ret = PyDict_SetItem(self->cur_file_data, this_line, Py_None);
+                    Py_DECREF(this_line);
+                    if (ret < 0) {
+                        STATS( self->stats.errors++; )
+                        return RET_ERROR;
+                    }
+                }
+            }
+            self->last_line = frame->f_lineno;
+        }
+        break;
+
+    case PyTrace_EXCEPTION:
+        /* Some code (Python 2.3, and pyexpat anywhere) fires an exception event
+           without a return event.  To detect that, we'll keep a copy of the
+           parent frame for an exception event.  If the next event is in that
+           frame, then we must have returned without a return event.  We can
+           synthesize the missing event then.
+
+           Python itself fixed this problem in 2.4.  Pyexpat still has the bug.
+           I've reported the problem with pyexpat as http://bugs.python.org/issue6359 .
+           If it gets fixed, this code should still work properly.  Maybe some day
+           the bug will be fixed everywhere coverage.py is supported, and we can
+           remove this missing-return detection.
+
+           More about this fix: http://nedbatchelder.com/blog/200907/a_nasty_little_bug.html
+        */
+        STATS( self->stats.exceptions++; )
+        self->last_exc_back = frame->f_back;
+        self->last_exc_firstlineno = frame->f_code->co_firstlineno;
+        break;
+
+    default:
+        STATS( self->stats.others++; )
+        break;
+    }
+
+    return RET_OK;
+}
+
+/*
+ * Python has two ways to set the trace function: sys.settrace(fn), which
+ * takes a Python callable, and PyEval_SetTrace(func, obj), which takes
+ * a C function and a Python object.  The way these work together is that
+ * sys.settrace(pyfn) calls PyEval_SetTrace(builtin_func, pyfn), using the
+ * Python callable as the object in PyEval_SetTrace.  So sys.gettrace()
+ * simply returns the Python object used as the second argument to
+ * PyEval_SetTrace.  So sys.gettrace() will return our self parameter, which
+ * means it must be callable to be used in sys.settrace().
+ *
+ * So we make our self callable, equivalent to invoking our trace function.
+ *
+ * To help with the process of replaying stored frames, this function has an
+ * optional keyword argument:
+ *
+ *      def CTracer_call(frame, event, arg, lineno=0)
+ *
+ * If provided, the lineno argument is used as the line number, and the
+ * frame's f_lineno member is ignored.
+ */
+static PyObject *
+CTracer_call(CTracer *self, PyObject *args, PyObject *kwds)
+{
+    PyFrameObject *frame;
+    PyObject *what_str;
+    PyObject *arg;
+    int lineno = 0;
+    int what;
+    int orig_lineno;
+    PyObject *ret = NULL;
+
+    static char *what_names[] = {
+        "call", "exception", "line", "return",
+        "c_call", "c_exception", "c_return",
+        NULL
+        };
+
+    #if WHAT_LOG
+    printf("pytrace\n");
+    #endif
+
+    static char *kwlist[] = {"frame", "event", "arg", "lineno", NULL};
+
+    if (!PyArg_ParseTupleAndKeywords(args, kwds, "O!O!O|i:Tracer_call", kwlist,
+            &PyFrame_Type, &frame, &MyText_Type, &what_str, &arg, &lineno)) {
+        goto done;
+    }
+
+    /* In Python, the what argument is a string, we need to find an int
+       for the C function. */
+    for (what = 0; what_names[what]; what++) {
+        PyObject *ascii = MyText_AS_BYTES(what_str);
+        int should_break = !strcmp(MyText_AS_STRING(ascii), what_names[what]);
+        Py_DECREF(ascii);
+        if (should_break) {
+            break;
+        }
+    }
+
+    /* Save off the frame's lineno, and use the forced one, if provided. */
+    orig_lineno = frame->f_lineno;
+    if (lineno > 0) {
+        frame->f_lineno = lineno;
+    }
+
+    /* Invoke the C function, and return ourselves. */
+    if (CTracer_trace(self, frame, what, arg) == RET_OK) {
+        Py_INCREF(self);
+        ret = (PyObject *)self;
+    }
+
+    /* Clean up. */
+    frame->f_lineno = orig_lineno;
+
+done:
+    return ret;
+}
+
+static PyObject *
+CTracer_start(CTracer *self, PyObject *args_unused)
+{
+    PyEval_SetTrace((Py_tracefunc)CTracer_trace, (PyObject*)self);
+    self->started = 1;
+    self->tracing_arcs = self->arcs && PyObject_IsTrue(self->arcs);
+    self->last_line = -1;
+
+    /* start() returns a trace function usable with sys.settrace() */
+    Py_INCREF(self);
+    return (PyObject *)self;
+}
+
+static PyObject *
+CTracer_stop(CTracer *self, PyObject *args_unused)
+{
+    if (self->started) {
+        PyEval_SetTrace(NULL, NULL);
+        self->started = 0;
+    }
+
+    return Py_BuildValue("");
+}
+
+static PyObject *
+CTracer_get_stats(CTracer *self)
+{
+#if COLLECT_STATS
+    return Py_BuildValue(
+        "{sI,sI,sI,sI,sI,sI,sI,sI,si,sI}",
+        "calls", self->stats.calls,
+        "lines", self->stats.lines,
+        "returns", self->stats.returns,
+        "exceptions", self->stats.exceptions,
+        "others", self->stats.others,
+        "new_files", self->stats.new_files,
+        "missed_returns", self->stats.missed_returns,
+        "stack_reallocs", self->stats.stack_reallocs,
+        "stack_alloc", self->data_stack_alloc,
+        "errors", self->stats.errors
+        );
+#else
+    return Py_BuildValue("");
+#endif /* COLLECT_STATS */
+}
+
+static PyMemberDef
+CTracer_members[] = {
+    { "should_trace",       T_OBJECT, offsetof(CTracer, should_trace), 0,
+            PyDoc_STR("Function indicating whether to trace a file.") },
+
+    { "warn",               T_OBJECT, offsetof(CTracer, warn), 0,
+            PyDoc_STR("Function for issuing warnings.") },
+
+    { "data",               T_OBJECT, offsetof(CTracer, data), 0,
+            PyDoc_STR("The raw dictionary of trace data.") },
+
+    { "should_trace_cache", T_OBJECT, offsetof(CTracer, should_trace_cache), 0,
+            PyDoc_STR("Dictionary caching should_trace results.") },
+
+    { "arcs",               T_OBJECT, offsetof(CTracer, arcs), 0,
+            PyDoc_STR("Should we trace arcs, or just lines?") },
+
+    { NULL }
+};
+
+static PyMethodDef
+CTracer_methods[] = {
+    { "start",      (PyCFunction) CTracer_start,        METH_VARARGS,
+            PyDoc_STR("Start the tracer") },
+
+    { "stop",       (PyCFunction) CTracer_stop,         METH_VARARGS,
+            PyDoc_STR("Stop the tracer") },
+
+    { "get_stats",  (PyCFunction) CTracer_get_stats,    METH_VARARGS,
+            PyDoc_STR("Get statistics about the tracing") },
+
+    { NULL }
+};
+
+static PyTypeObject
+CTracerType = {
+    MyType_HEAD_INIT
+    "coverage.CTracer",        /*tp_name*/
+    sizeof(CTracer),           /*tp_basicsize*/
+    0,                         /*tp_itemsize*/
+    (destructor)CTracer_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 */
+    (ternaryfunc)CTracer_call, /*tp_call*/
+    0,                         /*tp_str*/
+    0,                         /*tp_getattro*/
+    0,                         /*tp_setattro*/
+    0,                         /*tp_as_buffer*/
+    Py_TPFLAGS_DEFAULT | Py_TPFLAGS_BASETYPE, /*tp_flags*/
+    "CTracer objects",         /* tp_doc */
+    0,                         /* tp_traverse */
+    0,                         /* tp_clear */
+    0,                         /* tp_richcompare */
+    0,                         /* tp_weaklistoffset */
+    0,                         /* tp_iter */
+    0,                         /* tp_iternext */
+    CTracer_methods,           /* tp_methods */
+    CTracer_members,           /* tp_members */
+    0,                         /* tp_getset */
+    0,                         /* tp_base */
+    0,                         /* tp_dict */
+    0,                         /* tp_descr_get */
+    0,                         /* tp_descr_set */
+    0,                         /* tp_dictoffset */
+    (initproc)CTracer_init,    /* tp_init */
+    0,                         /* tp_alloc */
+    0,                         /* tp_new */
+};
+
+/* Module definition */
+
+#define MODULE_DOC PyDoc_STR("Fast coverage tracer.")
+
+#if PY_MAJOR_VERSION >= 3
+
+static PyModuleDef
+moduledef = {
+    PyModuleDef_HEAD_INIT,
+    "coverage.tracer",
+    MODULE_DOC,
+    -1,
+    NULL,       /* methods */
+    NULL,
+    NULL,       /* traverse */
+    NULL,       /* clear */
+    NULL
+};
+
+
+PyObject *
+PyInit_tracer(void)
+{
+    PyObject * mod = PyModule_Create(&moduledef);
+    if (mod == NULL) {
+        return NULL;
+    }
+
+    CTracerType.tp_new = PyType_GenericNew;
+    if (PyType_Ready(&CTracerType) < 0) {
+        Py_DECREF(mod);
+        return NULL;
+    }
+
+    Py_INCREF(&CTracerType);
+    PyModule_AddObject(mod, "CTracer", (PyObject *)&CTracerType);
+
+    return mod;
+}
+
+#else
+
+void
+inittracer(void)
+{
+    PyObject * mod;
+
+    mod = Py_InitModule3("coverage.tracer", NULL, MODULE_DOC);
+    if (mod == NULL) {
+        return;
+    }
+
+    CTracerType.tp_new = PyType_GenericNew;
+    if (PyType_Ready(&CTracerType) < 0) {
+        return;
+    }
+
+    Py_INCREF(&CTracerType);
+    PyModule_AddObject(mod, "CTracer", (PyObject *)&CTracerType);
+}
+
+#endif /* Py3k */