diff --git a/ncurses/base/safe_sprintf.c b/ncurses/base/safe_sprintf.c
index 34abd2f..8816e58 100644
--- a/ncurses/base/safe_sprintf.c
+++ b/ncurses/base/safe_sprintf.c
@@ -1,5 +1,6 @@
 /****************************************************************************
- * Copyright (c) 1998-2012,2013 Free Software Foundation, Inc.              *
+ * Copyright 2018-2021,2023 Thomas E. Dickey                                *
+ * Copyright 1998-2012,2013 Free Software Foundation, Inc.                  *
  *                                                                          *
  * Permission is hereby granted, free of charge, to any person obtaining a  *
  * copy of this software and associated documentation files (the            *
@@ -33,7 +34,7 @@
 #include <curses.priv.h>
 #include <ctype.h>
 
-MODULE_ID("$Id: safe_sprintf.c,v 1.27 2013/01/20 01:04:32 tom Exp $")
+MODULE_ID("$Id: safe_sprintf.c,v 1.37 2023/09/30 10:42:42 tom Exp $")
 
 #if USE_SAFE_SPRINTF
 
@@ -41,7 +42,7 @@
     Flags, Width, Prec, Type, Format
 } PRINTF;
 
-#define VA_INTGR(type) ival = va_arg(ap, type)
+#define VA_INTGR(type) ival = (int) va_arg(ap, type)
 #define VA_FLOAT(type) fval = va_arg(ap, type)
 #define VA_POINT(type) pval = (void *)va_arg(ap, type)
 
@@ -157,9 +158,9 @@
 		    case 's':
 			VA_POINT(char *);
 			if (prec < 0)
-			    prec = strlen(pval);
+			    prec = (int) strlen(pval);
 			if (prec > (int) length) {
-			    length = length + prec;
+			    length = length + (size_t) prec;
 			    buffer = typeRealloc(char, length, buffer);
 			    if (buffer == 0) {
 				free(format);
@@ -222,9 +223,9 @@
 				    const char *fmt,
 				    va_list ap)
 {
-    char *result = 0;
+    char *result = NULL;
 
-    if (fmt != 0) {
+    if (SP_PARM != NULL && fmt != NULL) {
 #if USE_SAFE_SPRINTF
 	va_list ap2;
 	int len;
@@ -234,10 +235,10 @@
 	end_va_copy(ap2);
 
 	if ((int) my_length < len + 1) {
-	    my_length = 2 * (len + 1);
+	    my_length = (size_t) (2 * (len + 1));
 	    my_buffer = typeRealloc(char, my_length, my_buffer);
 	}
-	if (my_buffer != 0) {
+	if (my_buffer != NULL) {
 	    *my_buffer = '\0';
 	    if (len >= 0) {
 		vsprintf(my_buffer, fmt, ap);
@@ -254,21 +255,37 @@
 	    if (screen_columns(SP_PARM) > MyCols)
 		MyCols = screen_columns(SP_PARM);
 	    my_length = (size_t) (MyRows * (MyCols + 1)) + 1;
+	    if (my_length < 80)
+		my_length = 80;
 	    my_buffer = typeRealloc(char, my_length, my_buffer);
 	}
 
-	if (my_buffer != 0) {
+	if (my_buffer != NULL) {
 # if HAVE_VSNPRINTF
-	    vsnprintf(my_buffer, my_length, fmt, ap);	/* GNU extension */
+	    /* SUSv2, 1997 */
+	    int used;
+
+	    do {
+		va_list ap2;
+
+		begin_va_copy(ap2, ap);
+		used = vsnprintf(my_buffer, my_length, fmt, ap2);
+		end_va_copy(ap2);
+		if (used < (int) my_length)
+		    break;
+		my_length = (size_t) ((3 * used) / 2);
+		my_buffer = typeRealloc(char, my_length, my_buffer);
+	    } while (my_buffer != NULL);
 # else
-	    vsprintf(my_buffer, fmt, ap);	/* ANSI */
+	    /* ISO/ANSI C, 1989 */
+	    vsprintf(my_buffer, fmt, ap);
 # endif
 	    result = my_buffer;
 	}
 #endif
-    } else if (my_buffer != 0) {	/* see _nc_freeall() */
+    } else if (my_buffer != NULL) {	/* see _nc_freeall() */
 	free(my_buffer);
-	my_buffer = 0;
+	my_buffer = NULL;
 	my_length = 0;
     }
     return result;