Re: [PATCH v3 2/2] xgethostname: handle long hostnames

[Jonathan Nieder]

Hi,

David Turner wrote:

> If the full hostname doesn't fit in the buffer supplied to
> gethostname, POSIX does not specify whether the buffer will be
> null-terminated, so to be safe, we should do it ourselves.  Introduce
> new function, xgethostname, which ensures that there is always a \0
> at the end of the buffer.

I think we should detect the error instead of truncating the hostname.
That (on top of your patch) would look like the following.

Thoughts?
Jonathan

diff --git i/wrapper.c w/wrapper.c
index d837417709..e218bd3bef 100644
--- i/wrapper.c
+++ w/wrapper.c
@@ -660,11 +660,13 @@ int xgethostname(char *buf, size_t len)
 {
        /*
         * If the full hostname doesn't fit in buf, POSIX does not
-        * specify whether the buffer will be null-terminated, so to
-        * be safe, do it ourselves.
+        * guarantee that an error will be returned. Check for ourselves
+        * to be safe.
         */
        int ret = gethostname(buf, len);
-       if (!ret)
-               buf[len - 1] = 0;
+       if (!ret && !memchr(buf, 0, len)) {
+               errno = ENAMETOOLONG;
+               return -1;
+       }
        return ret;
 }