[avr-libc-dev] [PATCH] printf: %s arguments with precision

[Christopher Hoover]

printf and friends improperly handle non-null termnated strings when a
%s argument has a precision.

"improperly handle" in this case is often a fatal error as the
function is doing (effectively) strlen().  :-(

here's a patch.

-ch

ch(a)murgatroid.com


--- avr-libc-1.0.2/libc/stdio/vfprintf.c        2003-01-02 08:27:43.000000000 
-0800
+++ avr-libc-1.0.2.ch/libc/stdio/vfprintf.c     2004-02-01 12:36:41.000000000 
-0800
@@ -332,12 +332,14 @@ vfprintf(FILE *stream, const char *fmt, 
                                        goto nextitem;
                                case 's':
                                        a.pc = va_arg(ap, char *);
-                                       for (base = 0; a.pc[base]; base++)
-                                               ; /* calc length of string */
 #if PRINTF_LEVEL > PRINTF_MIN
-                                       if ((flags & FLPREC) && prec < base)
-                                               base = prec;
+                                       if (flags & FLPREC)
+                                               base = strnlen(a.pc, prec);
+                                       else
+                                               base = strlen(a.pc);
                                        width -= base;
+#else
+                                       base = strlen(a.pc);
 #endif
                                        goto nextitem;
                                case 'd':