Date: Wed, 28 Nov 2001 21:48:58 -0700 From: Wes Peters <wes@softweyr.com> To: Bill Fenner <fenner@research.att.com> Cc: mike@FreeBSD.org, freebsd-standards@bostonradio.org Subject: Re: strerror_r() implementation Message-ID: <3C05BE3A.1DF1A539@softweyr.com> References: <20011125014216.A84711@espresso.q9media.com> <3C00A43B.9929E9C7@softweyr.com> <200111281854.KAA13574@windsor.research.att.com>
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Bill Fenner wrote:
>
> I'm still confused by why you need ERR_LEN; strerror() does:
>
> if (uerr < sys_nerr)
> return (char *)sys_errlist[uerr];
>
> so the only possible return value from strerror_r() is stored in
> strerror_r()'s tmp[40] -- so strerror() can stick with ebuf[40].
No. The array tmp[] is used only to collect the ASCII version of the
errno *in reverse*. The strlcpy seeds strerrbuf with the string
"Unknown error: ". The loop following strlcpy un-reverses the ascii
error number onto the end of the string.
Ah, I see the confusion. The size of ebuf in strerror doesn't need to
be big enough to hold messages from sys_errlist, it only needs to be
large enough to hold "Unknown error: " plus the length of a 64-bit
number in ascii.
How does this look?
--- strerror.c.nxt Wed Nov 28 20:32:54 2001
+++ strerror.c Wed Nov 28 20:39:30 2001
@@ -86,18 +86,17 @@
}
-/*
- * NOTE: the following length should be enough to hold the longest defined
- * error message in sys_errlist, defined in ../gen/errlst.c. This is a WAG
- * that is better than the previous value.
- */
-#define ERR_LEN 64
-
char *
strerror(num)
int num;
{
unsigned int uerr;
+
+ /*
+ * NOTE: the following length should be enough to hold the
+ * longest "Unknown error: " message above.
+ */
+#define ERR_LEN 55
static char ebuf[ERR_LEN];
uerr = num; /* convert to unsigned */
@@ -106,7 +105,7 @@
/* strerror can't fail so handle truncation semi-elegantly */
if (strerror_r(num, ebuf, (size_t) ERR_LEN) != 0)
- ebuf[ERR_LEN - 1] = '\0';
+ ebuf[ERR_LEN - 1] = '\0';
return ebuf;
}
The last change is a whitespace error. Mustn't have any style(9) nits,
right? ;^)
--
"Where am I, and what am I doing in this handbasket?"
Wes Peters Softweyr LLC
wes@softweyr.com http://softweyr.com/
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