more consistent function behaviour

bitarray/_bitarray.c

@@ -608,9 +608,9 @@ find_bit(bitarrayobject *self, int vi, Py_ssize_t a, Py_ssize_t b, int right)
     return -1;
 }
 
-/* Returns:
-   -1: on error and sets exception
- 0, 1: value of integer sub or first item of sub if bitarray of length 1
+/* Given sub_bitarray, return:
+   -1: on error (after setting exception)
+ 0, 1: value of integer sub or single item of sub if bitarray of length 1
     2: when sub is bitarray of length 0, 2, 3, ...
  */
 static int
@@ -2593,7 +2593,7 @@ bitwise_check(PyObject *a, PyObject *b, const char *ostr)
         return -1;
     }
 
-    if (unequal_size_or_endian((bitarrayobject *) a, (bitarrayobject *) b))
+    if (ensure_eq_size_endian((bitarrayobject *) a, (bitarrayobject *) b) < 0)
         return -1;
 
     return 0;

bitarray/_util.c

@@ -246,7 +246,7 @@ binary_function(PyObject *args, const char *format, const char oper)
                           bitarray_type_obj, (PyObject *) &a,
                           bitarray_type_obj, (PyObject *) &b))
         return NULL;
-    if (unequal_size_or_endian(a, b))
+    if (ensure_eq_size_endian(a, b) < 0)
         return NULL;
 
     wbuff_a = WBUFF(a);
@@ -352,7 +352,7 @@ correspond_all(PyObject *module, PyObject *args)
                           bitarray_type_obj, (PyObject *) &a,
                           bitarray_type_obj, (PyObject *) &b))
         return NULL;
-    if (unequal_size_or_endian(a, b))
+    if (ensure_eq_size_endian(a, b) < 0)
         return NULL;
 
     cwords = a->nbits / 64;     /* complete 64-bit words */

bitarray/bitarray.h

@@ -317,20 +317,20 @@ conv_pybit(PyObject *value, int *vi)
     return 1;
 }
 
-/* return 1 when a and b have unequal length or bit-endianness and set
-   exception, otherwise (when length and endianness are equal) return 0 */
+/* Return 0 if bitarrays have equal length and bit-endianness.
+   Otherwise, set exception and return -1. */
 static inline int
-unequal_size_or_endian(bitarrayobject *a, bitarrayobject *b)
+ensure_eq_size_endian(bitarrayobject *a, bitarrayobject *b)
 {
     if (a->nbits != b->nbits) {
         PyErr_SetString(PyExc_ValueError,
                         "bitarrays of equal length expected");
-        return 1;
+        return -1;
     }
     if (a->endian != b->endian) {
         PyErr_SetString(PyExc_ValueError,
                         "bitarrays of equal bit-endianness expected");
-        return 1;
+        return -1;
     }
     return 0;
 }