patch 7.4.1863
Problem:    Compiler warnings on Win64.
Solution:   Adjust types, add type casts. (Ken Takata)
diff --git a/src/if_perl.xs b/src/if_perl.xs
index aab7ade..a489994 100644
--- a/src/if_perl.xs
+++ b/src/if_perl.xs
@@ -1075,7 +1075,8 @@
 	{
 	    size_t  len		= 0;
 	    char *  str_from	= SvPV(sv, len);
-	    char_u *str_to	= (char_u*)alloc(sizeof(char_u) * (len + 1));
+	    char_u *str_to	= (char_u*)alloc(
+				      (unsigned)(sizeof(char_u) * (len + 1)));
 
 	    if (str_to) {
 		str_to[len] = '\0';
@@ -1370,13 +1371,13 @@
     char_u *str;
     PerlIOVim * s = PerlIOSelf(f, PerlIOVim);
 
-    str = vim_strnsave((char_u *)vbuf, count);
+    str = vim_strnsave((char_u *)vbuf, (int)count);
     if (str == NULL)
 	return 0;
     msg_split((char_u *)str, s->attr);
     vim_free(str);
 
-    return count;
+    return (SSize_t)count;
 }
 
 static PERLIO_FUNCS_DECL(PerlIO_Vim) = {