diff -r 8c9769b17171 Objects/complexobject.c
--- a/Objects/complexobject.c	Mon Nov 04 07:44:29 2013 +0100
+++ b/Objects/complexobject.c	Sat Nov 23 20:48:28 2013 +0100
@@ -790,6 +790,12 @@
                         "complex() argument must be a string or a number");
         return NULL;
     }
+    if (len > INT_MAX) {
+        Py_XDECREF(s_buffer);
+        PyErr_SetString(PyExc_OverflowError,
+                        "complex() argument is too long.");
+        return NULL;
+    }
 
     /* position on first nonblank */
     start = s;
diff -r 8c9769b17171 Objects/floatobject.c
--- a/Objects/floatobject.c	Mon Nov 04 07:44:29 2013 +0100
+++ b/Objects/floatobject.c	Sat Nov 23 20:48:28 2013 +0100
@@ -204,6 +204,12 @@
             "float() argument must be a string or a number");
         return NULL;
     }
+    if (len > INT_MAX) {
+        Py_XDECREF(s_buffer);
+        PyErr_SetString(PyExc_OverflowError,
+                        "float() argument is too long.");
+        return NULL;
+    }
     last = s + len;
     /* strip space */
     while (s < last && Py_ISSPACE(*s))
diff -r 8c9769b17171 Python/dtoa.c
--- a/Python/dtoa.c	Mon Nov 04 07:44:29 2013 +0100
+++ b/Python/dtoa.c	Sat Nov 23 20:48:28 2013 +0100
@@ -1693,6 +1693,10 @@
                  * this for larger i values.
                  */
                 e -= i;
+                if (e < 0) {
+                    /* quick workaround for segfault Issue #19638 */
+                    goto failed_malloc;
+                }
                 dval(&rv) *= tens[i];
                 dval(&rv) *= tens[e];
                 goto ret;