Fix various cases where optimised division of constants did not check for division by 0.

Closes #2820.

6 files changed, 285 insertions, 9 deletions

diff --git a/Cython/Compiler/Optimize.py b/Cython/Compiler/Optimize.py
index 4c306d566..6c3a6b1c2 100644
--- a/Cython/Compiler/Optimize.py
+++ b/Cython/Compiler/Optimize.py
@@ -3166,6 +3166,7 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
                 PyrexTypes.CFuncTypeArg("op2", PyrexTypes.py_object_type, None),
                 PyrexTypes.CFuncTypeArg("cval", ctype, None),
                 PyrexTypes.CFuncTypeArg("inplace", PyrexTypes.c_bint_type, None),
+                PyrexTypes.CFuncTypeArg("zerodiv_check", PyrexTypes.c_bint_type, None),
             ], exception_value=None if ret_type.is_pyobject else ret_type.exception_value))
         for ctype in (PyrexTypes.c_long_type, PyrexTypes.c_double_type)
         for ret_type in (PyrexTypes.py_object_type, PyrexTypes.c_bint_type)
@@ -3297,12 +3298,20 @@ class OptimizeBuiltinCalls(Visitor.NodeRefCleanupMixin,
             # Cut off at an integer border that is still safe for all operations.
             return node
 
+        if operator in ('TrueDivide', 'FloorDivide', 'Divide', 'Remainder'):
+            if args[1].constant_result == 0:
+                # Don't optimise division by 0. :)
+                return node
+
         args = list(args)
         args.append((ExprNodes.FloatNode if is_float else ExprNodes.IntNode)(
             numval.pos, value=numval.value, constant_result=numval.constant_result,
             type=num_type))
         inplace = node.inplace if isinstance(node, ExprNodes.NumBinopNode) else False
         args.append(ExprNodes.BoolNode(node.pos, value=inplace, constant_result=inplace))
+        zerodivision_check = arg_order == 'CObj' and (
+            not node.cdivision if isinstance(node, ExprNodes.DivNode) else False)
+        args.append(ExprNodes.BoolNode(node.pos, value=zerodivision_check, constant_result=zerodivision_check))
 
         utility_code = TempitaUtilityCode.load_cached(
             "PyFloatBinop" if is_float else "PyIntCompare" if operator in ('Eq', 'Ne') else "PyIntBinop",
diff --git a/Cython/Utility/Optimize.c b/Cython/Utility/Optimize.c
index 3366f9cf0..8030befb9 100644
--- a/Cython/Utility/Optimize.c
+++ b/Cython/Utility/Optimize.c
@@ -787,9 +787,9 @@ static CYTHON_INLINE {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject els
 
 {{py: c_ret_type = 'PyObject*' if ret_type.is_pyobject else 'int'}}
 #if !CYTHON_COMPILING_IN_PYPY
-static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, long intval, int inplace); /*proto*/
+static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, long intval, int inplace, int zerodivision_check); /*proto*/
 #else
-#define __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(op1, op2, intval, inplace) \
+#define __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(op1, op2, intval, inplace, zerodivision_check) \
     {{if op in ('Eq', 'Ne')}}{{'' if ret_type.is_pyobject else '__Pyx_PyObject_IsTrueAndDecref'}}(PyObject_RichCompare(op1, op2, Py_{{op.upper()}}))
     {{else}}(inplace ? PyNumber_InPlace{{op}}(op1, op2) : PyNumber_{{op}}(op1, op2))
     {{endif}}
@@ -804,6 +804,8 @@ static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op
 {{py: return_true = 'Py_RETURN_TRUE' if ret_type.is_pyobject else 'return 1'}}
 {{py: return_false = 'Py_RETURN_FALSE' if ret_type.is_pyobject else 'return 0'}}
 {{py: slot_name = {'TrueDivide': 'true_divide', 'FloorDivide': 'floor_divide'}.get(op, op.lower()) }}
+{{py: cfunc_name = '__Pyx_PyInt_%s%s%s' % ('' if ret_type.is_pyobject else 'Bool', op, order)}}
+{{py: zerodiv_check = lambda operand, _cfunc_name=cfunc_name: '%s_ZeroDivisionError(%s)' % (_cfunc_name, operand)}}
 {{py:
 c_op = {
     'Add': '+', 'Subtract': '-', 'Remainder': '%', 'TrueDivide': '/', 'FloorDivide': '/',
@@ -812,7 +814,21 @@ c_op = {
     }[op]
 }}
 
-static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, CYTHON_UNUSED long intval, CYTHON_UNUSED int inplace) {
+{{if op in ('TrueDivide', 'FloorDivide', 'Remainder')}}
+#if PY_MAJOR_VERSION < 3 || CYTHON_USE_PYLONG_INTERNALS
+#define {{zerodiv_check('operand')}} \
+    if (unlikely(zerodivision_check && ((operand) == 0))) { \
+        PyErr_SetString(PyExc_ZeroDivisionError, "integer division{{if op == 'Remainder'}} or modulo{{endif}} by zero"); \
+        return NULL; \
+    }
+#endif
+{{endif}}
+
+static {{c_ret_type}} {{cfunc_name}}(PyObject *op1, PyObject *op2, CYTHON_UNUSED long intval, int inplace, int zerodivision_check) {
+    // Prevent "unused" warnings.
+    (void)inplace;
+    (void)zerodivision_check;
+
     {{if op in ('Eq', 'Ne')}}
     if (op1 == op2) {
         {{return_true if op == 'Eq' else return_false}};
@@ -841,18 +857,21 @@ static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op
                 return PyInt_FromLong(x);
             return PyLong_Type.tp_as_number->nb_{{slot_name}}(op1, op2);
         {{elif c_op == '%'}}
+            {{zerodiv_check('b')}}
             // see ExprNodes.py :: mod_int_utility_code
             x = a % b;
             x += ((x != 0) & ((x ^ b) < 0)) * b;
             return PyInt_FromLong(x);
         {{elif op == 'TrueDivide'}}
+            {{zerodiv_check('b')}}
             if (8 * sizeof(long) <= 53 || likely(labs({{ival}}) <= ((PY_LONG_LONG)1 << 53))) {
                 return PyFloat_FromDouble((double)a / (double)b);
             }
             // let Python do the rounding
             return PyInt_Type.tp_as_number->nb_{{slot_name}}(op1, op2);
         {{elif op == 'FloorDivide'}}
-            // INT_MIN / -1  is the only case that overflows
+            // INT_MIN / -1  is the only case that overflows, b == 0 is an error case
+            {{zerodiv_check('b')}}
             if (unlikely(b == -1 && ((unsigned long)a) == 0-(unsigned long)a))
                 return PyInt_Type.tp_as_number->nb_{{slot_name}}(op1, op2);
             else {
@@ -934,16 +953,19 @@ static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op
             }
         {{else}}
             {{if c_op == '%'}}
+                {{zerodiv_check('b')}}
                 // see ExprNodes.py :: mod_int_utility_code
                 x = a % b;
                 x += ((x != 0) & ((x ^ b) < 0)) * b;
             {{elif op == 'TrueDivide'}}
+                {{zerodiv_check('b')}}
                 if ((8 * sizeof(long) <= 53 || likely(labs({{ival}}) <= ((PY_LONG_LONG)1 << 53)))
-                    || __Pyx_sst_abs(size) <= 52 / PyLong_SHIFT) {
+                        || __Pyx_sst_abs(size) <= 52 / PyLong_SHIFT) {
                     return PyFloat_FromDouble((double)a / (double)b);
                 }
                 return PyLong_Type.tp_as_number->nb_{{slot_name}}(op1, op2);
             {{elif op == 'FloorDivide'}}
+                {{zerodiv_check('b')}}
                 {
                     long q, r;
                     // see ExprNodes.py :: div_int_utility_code
@@ -1008,6 +1030,12 @@ static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op
             }
         {{else}}
             double result;
+            {{if op == 'TrueDivide'}}
+            if (unlikely(zerodivision_check && b == 0)) {
+                PyErr_SetString(PyExc_ZeroDivisionError, "float division by zero");
+                return NULL;
+            }
+            {{endif}}
             // copied from floatobject.c in Py3.5:
             PyFPE_START_PROTECT("{{op.lower() if not op.endswith('Divide') else 'divide'}}", return NULL)
             result = ((double)a) {{c_op}} (double)b;
@@ -1030,9 +1058,9 @@ static {{c_ret_type}} __Pyx_PyInt_{{'' if ret_type.is_pyobject else 'Bool'}}{{op
 
 {{py: c_ret_type = 'PyObject*' if ret_type.is_pyobject else 'int'}}
 #if !CYTHON_COMPILING_IN_PYPY
-static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, double floatval, int inplace); /*proto*/
+static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, double floatval, int inplace, int zerodivision_check); /*proto*/
 #else
-#define __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(op1, op2, floatval, inplace) \
+#define __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(op1, op2, floatval, inplace, zerodivision_check) \
     {{if op in ('Eq', 'Ne')}}{{'' if ret_type.is_pyobject else '__Pyx_PyObject_IsTrueAndDecref'}}(PyObject_RichCompare(op1, op2, Py_{{op.upper()}}))
     {{elif op == 'Divide'}}((inplace ? __Pyx_PyNumber_InPlaceDivide(op1, op2) : __Pyx_PyNumber_Divide(op1, op2)))
     {{else}}(inplace ? PyNumber_InPlace{{op}}(op1, op2) : PyNumber_{{op}}(op1, op2))
@@ -1047,6 +1075,8 @@ static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{
 {{py: return_true = 'Py_RETURN_TRUE' if ret_type.is_pyobject else 'return 1'}}
 {{py: return_false = 'Py_RETURN_FALSE' if ret_type.is_pyobject else 'return 0'}}
 {{py: pyval, fval = ('op2', 'b') if order == 'CObj' else ('op1', 'a') }}
+{{py: cfunc_name = '__Pyx_PyFloat_%s%s%s' % ('' if ret_type.is_pyobject else 'Bool', op, order) }}
+{{py: zerodiv_check = lambda operand, _cfunc_name=cfunc_name: '%s_ZeroDivisionError(%s)' % (_cfunc_name, operand)}}
 {{py:
 c_op = {
     'Add': '+', 'Subtract': '-', 'TrueDivide': '/', 'Divide': '/', 'Remainder': '%',
@@ -1054,9 +1084,19 @@ c_op = {
     }[op]
 }}
 
-static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{op}}{{order}}(PyObject *op1, PyObject *op2, double floatval, CYTHON_UNUSED int inplace) {
+{{if order == 'CObj' and c_op in '%/'}}
+#define {{zerodiv_check('operand')}} if (unlikely(zerodivision_check && ((operand) == 0))) { \
+    PyErr_SetString(PyExc_ZeroDivisionError, "integer division{{if op == 'Remainder'}} or modulo{{endif}} by zero"); \
+    return NULL; \
+}
+{{endif}}
+
+static {{c_ret_type}} {{cfunc_name}}(PyObject *op1, PyObject *op2, double floatval, int inplace, int zerodivision_check) {
     const double {{'a' if order == 'CObj' else 'b'}} = floatval;
     double {{fval}}{{if op not in ('Eq', 'Ne')}}, result{{endif}};
+    // Prevent "unused" warnings.
+    (void)inplace;
+    (void)zerodivision_check;
 
     {{if op in ('Eq', 'Ne')}}
     if (op1 == op2) {
@@ -1066,11 +1106,13 @@ static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{
 
     if (likely(PyFloat_CheckExact({{pyval}}))) {
         {{fval}} = PyFloat_AS_DOUBLE({{pyval}});
+        {{if order == 'CObj' and c_op in '%/'}}{{zerodiv_check(fval)}}{{endif}}
     } else
 
     #if PY_MAJOR_VERSION < 3
     if (likely(PyInt_CheckExact({{pyval}}))) {
         {{fval}} = (double) PyInt_AS_LONG({{pyval}});
+        {{if order == 'CObj' and c_op in '%/'}}{{zerodiv_check(fval)}}{{endif}}
     } else
     #endif
 
@@ -1079,7 +1121,7 @@ static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{
         const digit* digits = ((PyLongObject*){{pyval}})->ob_digit;
         const Py_ssize_t size = Py_SIZE({{pyval}});
         switch (size) {
-            case  0: {{fval}} = 0.0; break;
+            case  0: {{if order == 'CObj' and c_op in '%/'}}{{zerodiv_check('0')}}{{else}}{{fval}} = 0.0;{{endif}} break;
             case -1: {{fval}} = -(double) digits[0]; break;
             case  1: {{fval}} = (double) digits[0]; break;
             {{for _size in (2, 3, 4)}}
@@ -1111,6 +1153,7 @@ static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{
         {{else}}
             {{fval}} = PyLong_AsDouble({{pyval}});
             if (unlikely({{fval}} == -1.0 && PyErr_Occurred())) return NULL;
+            {{if order == 'CObj' and c_op in '%/'}}{{zerodiv_check(fval)}}{{endif}}
         {{endif}}
         }
     } else {
@@ -1132,6 +1175,7 @@ static {{c_ret_type}} __Pyx_PyFloat_{{'' if ret_type.is_pyobject else 'Bool'}}{{
         }
     {{else}}
         // copied from floatobject.c in Py3.5:
+        {{if order == 'CObj' and c_op in '%/'}}{{zerodiv_check('b')}}{{endif}}
         PyFPE_START_PROTECT("{{op.lower() if not op.endswith('Divide') else 'divide'}}", return NULL)
         {{if c_op == '%'}}
         result = fmod(a, b);
diff --git a/tests/run/float_division.pyx b/tests/run/float_division.pyx
index 36d600938..2c2630f10 100644
--- a/tests/run/float_division.pyx
+++ b/tests/run/float_division.pyx
@@ -26,6 +26,39 @@ def float_by_float():
     return 3.0 / 2.0
 
 
+def div_by_0(x):
+    """
+    >>> div_by_0(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(1)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(1.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> float('inf') / 0.0  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(float('inf'))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(float('-inf'))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> float('nan') / 0.0  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_by_0(float('nan'))  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    """
+    return x / 0.0
+
+
 def div_1_by(x):
     """
     >>> div_1_by(1.0)
@@ -42,6 +75,12 @@ def div_1_by(x):
     -0.0
     >>> div_1_by(float('nan'))
     nan
+    >>> div_1_by(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_1_by(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
     """
     return 1.0 / x
 
@@ -116,6 +155,12 @@ def div_neg_2_by(x):
     nan
     >>> div_neg_2_by(float('nan'))
     nan
+    >>> div_neg_2_by(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_neg_2_by(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
     """
     return (-2.0) / x
 
@@ -148,6 +193,12 @@ def div_nan_by(x):
     nan
     >>> div_nan_by(float('nan'))
     nan
+    >>> div_nan_by(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_nan_by(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
     """
     return float("nan") / x
 
@@ -182,6 +233,15 @@ def div_inf_by(x):
     nan
     >>> div_inf_by(float('-inf'))
     nan
+    >>> float("inf") / 0.0  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_inf_by(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_inf_by(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
     """
     return float("inf") / x
 
@@ -196,5 +256,14 @@ def div_neg_inf_by(x):
     inf
     >>> div_neg_inf_by(-1.0)
     inf
+    >>> float("-inf") / 0.0  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_neg_inf_by(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
+    >>> div_neg_inf_by(0.0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division by zero
     """
     return float("-inf") / x
diff --git a/tests/run/future_division.pyx b/tests/run/future_division.pyx
index 58208c6f9..737fb06d3 100644
--- a/tests/run/future_division.pyx
+++ b/tests/run/future_division.pyx
@@ -157,3 +157,73 @@ def int_int(int a, int b):
     (0.5, 2.0)
     """
     return a/b, b/a
+
+
+def div_by_0(a):
+    """
+    >>> div_by_0(0)
+    'OK'
+    >>> div_by_0(0.0)
+    'OK'
+    """
+    try:
+        1/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 1"
+    try:
+        1//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 2"
+    try:
+        5.0/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 3"
+    try:
+        5.0//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 4"
+    try:
+        5/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 5"
+    try:
+        5//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 6"
+    try:
+        (2**15)/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 7"
+    try:
+        (2**15)//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 8"
+    try:
+        (2**30)/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 9"
+    try:
+        (2**30)//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 10"
+    return 'OK'
diff --git a/tests/run/modop.pyx b/tests/run/modop.pyx
index 2b9a3380a..1402cbb54 100644
--- a/tests/run/modop.pyx
+++ b/tests/run/modop.pyx
@@ -7,11 +7,25 @@ def modobj(obj2, obj3):
     1
     >>> modobj('%d', 5)
     '5'
+    >>> modobj(1, 0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division...by zero
     """
     obj1 = obj2 % obj3
     return obj1
 
 
+def mod_10_obj(int2):
+    """
+    >>> mod_10_obj(0)  # doctest: +ELLIPSIS
+    Traceback (most recent call last):
+    ZeroDivisionError: ...division...by zero
+    >>> mod_10_obj(3)
+    1
+    """
+    return 10 % int2
+
+
 def mod_obj_10(int2):
     """
     >>> 0 % 10
diff --git a/tests/run/non_future_division.pyx b/tests/run/non_future_division.pyx
index 70bcd174f..d1d84549b 100644
--- a/tests/run/non_future_division.pyx
+++ b/tests/run/non_future_division.pyx
@@ -143,3 +143,73 @@ def int_int(int a, int b):
     (0, 2)
     """
     return a/b, b/a
+
+
+def div_by_0(a):
+    """
+    >>> div_by_0(0)
+    'OK'
+    >>> div_by_0(0.0)
+    'OK'
+    """
+    try:
+        1/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 1"
+    try:
+        1//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 2"
+    try:
+        5.0/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 3"
+    try:
+        5.0//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 4"
+    try:
+        5/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 5"
+    try:
+        5//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 6"
+    try:
+        (2**15)/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 7"
+    try:
+        (2**15)//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 8"
+    try:
+        (2**30)/a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 9"
+    try:
+        (2**30)//a
+    except ZeroDivisionError:
+        pass
+    else:
+        return "FAIL 10"
+    return 'OK'