[PATCH] compat/inet_ntop.c: Use INET_ADDRSTRLEN and INET6_ADDRSTRLEN macroses

[PATCH] compat/inet_ntop.c: Use INET_ADDRSTRLEN and INET6_ADDRSTRLEN macroses

[brilliantov]

From: Brilliantov Kirill Vladimirovich <brilliantov@inbox.ru>

Signed-off-by: Brilliantov Kirill Vladimirovich <brilliantov@inbox.ru>
---
 compat/inet_ntop.c | 4 ++--
 1 file changed, 2 insertions(+), 2 deletions(-)

diff --git a/compat/inet_ntop.c b/compat/inet_ntop.c
index 90b7cc4..fcd3b15 100644
--- a/compat/inet_ntop.c
+++ b/compat/inet_ntop.c
@@ -47,7 +47,7 @@ static const char *
 inet_ntop4(const u_char *src, char *dst, size_t size)
 {
 	static const char fmt[] = "%u.%u.%u.%u";
-	char tmp[sizeof "255.255.255.255"];
+	char tmp[INET_ADDRSTRLEN];
 	int nprinted;
 
 	nprinted = snprintf(tmp, sizeof(tmp), fmt, src[0], src[1], src[2], src[3]);
@@ -78,7 +78,7 @@ inet_ntop6(const u_char *src, char *dst, size_t size)
 	 * Keep this in mind if you think this function should have been coded
 	 * to use pointer overlays.  All the world's not a VAX.
 	 */
-	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
+	char tmp[INET6_ADDRSTRLEN], *tp;
 	struct { int base, len; } best, cur;
 	unsigned int words[NS_IN6ADDRSZ / NS_INT16SZ];
 	int i;
-- 
2.1.4

Re: [PATCH] compat/inet_ntop.c: Use INET_ADDRSTRLEN and INET6_ADDRSTRLEN macroses

[Johannes Schindelin]

Hi Kirill,

On 2015-08-25 12:34, brilliantov@inbox.ru wrote:
> From: Brilliantov Kirill Vladimirovich <brilliantov@inbox.ru>
> 
> Signed-off-by: Brilliantov Kirill Vladimirovich <brilliantov@inbox.ru>

The commit message makes for an excellent place to fill in the reader on information that is not obvious from reading the patch. For example...

> diff --git a/compat/inet_ntop.c b/compat/inet_ntop.c
> index 90b7cc4..fcd3b15 100644
> --- a/compat/inet_ntop.c
> +++ b/compat/inet_ntop.c
> @@ -47,7 +47,7 @@ static const char *
>  inet_ntop4(const u_char *src, char *dst, size_t size)
>  {
>  	static const char fmt[] = "%u.%u.%u.%u";
> -	char tmp[sizeof "255.255.255.255"];
> +	char tmp[INET_ADDRSTRLEN];

Given that we are in compat/ space, i.e. in a space meant for platforms lacking POSIX functions and definitions, is it really safe to assume that INET_ADDRSTRLEN is available there?

> @@ -78,7 +78,7 @@ inet_ntop6(const u_char *src, char *dst, size_t size)
>  	 * Keep this in mind if you think this function should have been coded
>  	 * to use pointer overlays.  All the world's not a VAX.
>  	 */
> -	char tmp[sizeof "ffff:ffff:ffff:ffff:ffff:ffff:255.255.255.255"], *tp;
> +	char tmp[INET6_ADDRSTRLEN], *tp;

Are we really, absolutely sure that INET6_ADDRSTRLEN is defined?

Also I wonder: what problem does this patch solve? Is the current way to determine the size of the `tmp` array incorrect?

Please use the commit message space to answer at least these questions.

Ciao,
Johannes