Fix SF 588452: debug build crashes on marshal.dumps([128] * 1000).

See there for a description.

Added test case.

Bugfix candidate for 2.2.x, not sure about previous versions:
probably low priority, because virtually no one runs debug builds.

Lib/test/test_marshal.py

@@ -39,3 +39,6 @@ for base in maxint64, minint64, -maxint64, -(minint64 >> 1):
             base = 0
         else:
             base >>= 1
+
+# Simple-minded check for SF 588452: Debug build crashes
+marshal.dumps([128] * 1000)

Python/marshal.c

@@ -84,17 +84,17 @@ w_string(char *s, int n, WFILE *p)
 static void
 w_short(int x, WFILE *p)
 {
-	w_byte( x      & 0xff, p);
-	w_byte((x>> 8) & 0xff, p);
+	w_byte((char)( x      & 0xff), p);
+	w_byte((char)((x>> 8) & 0xff), p);
 }
 
 static void
 w_long(long x, WFILE *p)
 {
-	w_byte((int)( x      & 0xff), p);
-	w_byte((int)((x>> 8) & 0xff), p);
-	w_byte((int)((x>>16) & 0xff), p);
-	w_byte((int)((x>>24) & 0xff), p);
+ 	w_byte((char)( x      & 0xff), p);
+ 	w_byte((char)((x>> 8) & 0xff), p);
+ 	w_byte((char)((x>>16) & 0xff), p);
+ 	w_byte((char)((x>>24) & 0xff), p);
 }
 
 #if SIZEOF_LONG > 4