Issue #5981: Fix some float.fromhex bugs related to inf and nan handling.

Lib/test/test_float.py

@@ -462,6 +462,11 @@ class HexFloatTestCase(unittest.TestCase):
             'snan',
             'NaNs',
             'nna',
+            'an',
+            'nf',
+            'nfinity',
+            'inity',
+            'iinity',
             '0xnan',
             '',
             ' ',
@@ -510,6 +515,32 @@ class HexFloatTestCase(unittest.TestCase):
                           'got %r instead' % (x, result))
 
 
+    def test_whitespace(self):
+        value_pairs = [
+            ('inf', INF),
+            ('-Infinity', -INF),
+            ('nan', NAN),
+            ('1.0', 1.0),
+            ('-0x.2', -0.125),
+            ('-0.0', -0.0)
+            ]
+        whitespace = [
+            '',
+            ' ',
+            '\t',
+            '\n',
+            '\n \t',
+            '\f',
+            '\v',
+            '\r'
+            ]
+        for inp, expected in value_pairs:
+            for lead in whitespace:
+                for trail in whitespace:
+                    got = fromHex(lead + inp + trail)
+                    self.identical(got, expected)
+
+
     def test_from_hex(self):
         MIN = self.MIN;
         MAX = self.MAX;

Misc/NEWS

@@ -12,6 +12,12 @@ What's New in Python 2.7 alpha 1
 Core and Builtins
 -----------------
 
+- Issue #5981: Fix three minor inf/nan issues in float.fromhex:
+  (1) inf and nan strings with trailing whitespace were incorrectly
+  rejected;  (2) parsing of strings representing infinities and nans
+  was locale aware; and (3) the interpretation of fromhex('-nan')
+  didn't match that of float('-nan').
+
 - Issue #5920: For float.__format__, change the behavior with the
   empty presentation type (that is, not one of 'e', 'f', 'g', or 'n')
   to be like 'g' but with at least one decimal point and with a

Objects/floatobject.c

@@ -1159,6 +1159,20 @@ Return a hexadecimal representation of a floating-point number.\n\
 >>> 3.14159.hex()\n\
 '0x1.921f9f01b866ep+1'");
 
+/* Case-insensitive locale-independent string match used for nan and inf
+   detection. t should be lower-case and null-terminated.  Return a nonzero
+   result if the first strlen(t) characters of s match t and 0 otherwise. */
+
+static int
+case_insensitive_match(const char *s, const char *t)
+{
+	while(*t && Py_TOLOWER(*s) == *t) {
+		s++;
+		t++;
+	}
+	return *t ? 0 : 1;
+}
+
 /* Convert a hexadecimal string to a float. */
 
 static PyObject *
@@ -1235,13 +1249,20 @@ float_fromhex(PyObject *cls, PyObject *arg)
 		s++;
 
 	/* infinities and nans */
-	if (PyOS_strnicmp(s, "nan", 4) == 0) {
-		x = Py_NAN;
+	if (*s == 'i' || *s == 'I') {
+		if (!case_insensitive_match(s+1, "nf"))
+			goto parse_error;
+		s += 3;
+		x = Py_HUGE_VAL;
+		if (case_insensitive_match(s, "inity"))
+			s += 5;
 		goto finished;
 	}
-	if (PyOS_strnicmp(s, "inf", 4) == 0 ||
-	    PyOS_strnicmp(s, "infinity", 9) == 0) {
-		x = sign*Py_HUGE_VAL;
+	if (*s == 'n' || *s == 'N') {
+		if (!case_insensitive_match(s+1, "an"))
+			goto parse_error;
+		s += 3;
+		x = Py_NAN;
 		goto finished;
 	}
 
@@ -1294,12 +1315,6 @@ float_fromhex(PyObject *cls, PyObject *arg)
 	else
 		exp = 0;
 
-	/* optional trailing whitespace leading to the end of the string */
-	while (Py_ISSPACE(*s))
-		s++;
-	if (s != s_end)
-		goto parse_error;
-
 /* for 0 <= j < ndigits, HEX_DIGIT(j) gives the jth most significant digit */
 #define HEX_DIGIT(j) hex_from_char(*((j) < fdigits ?		\
 				     coeff_end-(j) :			\
@@ -1313,7 +1328,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 	while (ndigits > 0 && HEX_DIGIT(ndigits-1) == 0)
 		ndigits--;
 	if (ndigits == 0 || exp < LONG_MIN/2) {
-		x = sign * 0.0;
+		x = 0.0;
 		goto finished;
 	}
 	if (exp > LONG_MAX/2)
@@ -1329,7 +1344,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 
 	/* catch almost all nonextreme cases of overflow and underflow here */
 	if (top_exp < DBL_MIN_EXP - DBL_MANT_DIG) {
-		x = sign * 0.0;
+		x = 0.0;
 		goto finished;
 	}
 	if (top_exp > DBL_MAX_EXP)
@@ -1344,7 +1359,7 @@ float_fromhex(PyObject *cls, PyObject *arg)
 		/* no rounding required */
 		for (i = ndigits-1; i >= 0; i--)
 			x = 16.0*x + HEX_DIGIT(i);
-		x = sign * ldexp(x, (int)(exp));
+		x = ldexp(x, (int)(exp));
 		goto finished;
 	}
 	/* rounding required.  key_digit is the index of the hex digit
@@ -1378,10 +1393,15 @@ float_fromhex(PyObject *cls, PyObject *arg)
 				goto overflow_error;
 		}
 	}
-	x = sign * ldexp(x, (int)(exp+4*key_digit));
+	x = ldexp(x, (int)(exp+4*key_digit));
 
   finished:
-	result_as_float = Py_BuildValue("(d)", x);
+	/* optional trailing whitespace leading to the end of the string */
+	while (Py_ISSPACE(*s))
+		s++;
+	if (s != s_end)
+		goto parse_error;
+	result_as_float = Py_BuildValue("(d)", sign * x);
 	if (result_as_float == NULL)
 		return NULL;
 	result = PyObject_CallObject(cls, result_as_float);