Issue #532631: Replace confusing fabs(x)/1e25 >= 1e25 test

with fabs(x) >= 1e50, and fix documentation.

Doc/library/stdtypes.rst

@@ -1409,7 +1409,7 @@ that ``'\0'`` is the end of the string.
 .. XXX Examples?
 
 For safety reasons, floating point precisions are clipped to 50; ``%f``
-conversions for numbers whose absolute value is over 1e25 are replaced by ``%g``
+conversions for numbers whose absolute value is over 1e50 are replaced by ``%g``
 conversions. [#]_  All other errors raise exceptions.
 
 .. index::

Objects/stringlib/formatter.h

@@ -789,7 +789,7 @@ format_float_internal(PyObject *value,
 
     if (precision < 0)
         precision = 6;
-    if (type == 'f' && (fabs(x) / 1e25) >= 1e25)
+    if (type == 'f' && fabs(x) >= 1e50)
         type = 'g';
 
     /* cast "type", because if we're in unicode we need to pass a

Objects/stringobject.c

@@ -4344,7 +4344,7 @@ formatfloat(char *buf, size_t buflen, int flags,
 	}
 	if (prec < 0)
 		prec = 6;
-	if (type == 'f' && fabs(x)/1e25 >= 1e25)
+	if (type == 'f' && fabs(x) >= 1e50)
 		type = 'g';
 	/* Worst case length calc to ensure no buffer overrun:
 

Objects/unicodeobject.c

@@ -8286,7 +8286,7 @@ formatfloat(Py_UNICODE *buf,
         return -1;
     if (prec < 0)
         prec = 6;
-    if (type == 'f' && (fabs(x) / 1e25) >= 1e25)
+    if (type == 'f' && fabs(x) >= 1e50)
         type = 'g';
     /* Worst case length calc to ensure no buffer overrun: