From 9a9a6365d5c5abb0fe3ec6cc09542e9c7e1d3bec Mon Sep 17 00:00:00 2001 From: Jones Desougi Date: Thu, 10 Jun 2010 15:04:51 +0200 Subject: *printf: Violation of precision with null string When a string format is processed and the argument is NULL, this yields "(null)" regardless of precision. This does not make sense, precision should not be exceeded. A simple test shows that glibc outputs nothing if precision is smaller than six and the attached patch implements this same behaviour. Consider the not uncommon case of strings implemented like this: struct string { int len; char *ptr; }; There is often no nultermination and they may be printed like this: printf("%.*s", string.len, string.ptr); If len is 0 then ptr may be anything, but NULL is a common value. Obviously the empty string would be expected, not "(null)". Signed-off-by: Jones Desougi Signed-off-by: Bernhard Reutner-Fischer --- libc/stdio/_vfprintf.c | 6 ++++++ 1 file changed, 6 insertions(+) (limited to 'libc/stdio/_vfprintf.c') diff --git a/libc/stdio/_vfprintf.c b/libc/stdio/_vfprintf.c index 3b007084d..fa5dc44fc 100644 --- a/libc/stdio/_vfprintf.c +++ b/libc/stdio/_vfprintf.c @@ -1670,6 +1670,9 @@ static int _do_one_spec(FILE * __restrict stream, #endif s = "(null)"; slen = 6; + /* Use an empty string rather than truncation if precision is too small. */ + if (ppfs->info.prec >= 0 && ppfs->info.prec < slen) + slen = 0; } } else { /* char */ s = buf; @@ -1726,6 +1729,9 @@ static int _do_one_spec(FILE * __restrict stream, NULL_STRING: s = "(null)"; SLEN = slen = 6; + /* Use an empty string rather than truncation if precision is too small. */ + if (ppfs->info.prec >= 0 && ppfs->info.prec < slen) + SLEN = slen = 0; } } else { /* char */ *wbuf = btowc( (unsigned char)(*((const int *) *argptr)) ); -- cgit v1.2.3