[Date Prev][Date Next][Thread Prev][Thread Next][Date Index][Thread Index]
Re: [PATCH v3] tools/libs/stat: fix broken build
On 02.10.20 08:20, Jan Beulich wrote:
On 02.10.2020 06:50, Jürgen Groß wrote:
On 01.10.20 18:38, Bertrand Marquis wrote:
Hi Juergen,
On 14 Sep 2020, at 11:58, Bertrand Marquis <bertrand.marquis@xxxxxxx> wrote:
On 12 Sep 2020, at 14:08, Juergen Gross <jgross@xxxxxxxx> wrote:
Making getBridge() static triggered a build error with some gcc versions:
error: 'strncpy' output may be truncated copying 15 bytes from a string of
length 255 [-Werror=stringop-truncation]
Fix that by using a buffer with 256 bytes instead.
Fixes: 6d0ec053907794 ("tools: split libxenstat into new tools/libs/stat
directory")
Signed-off-by: Juergen Gross <jgross@xxxxxxxx>
Reviewed-by: Bertrand Marquis <bertrand.marquis@xxxxxxx>
Sorry i have to come back on this one.
I still see an error compiling with Yocto on this one:
| inlined from 'xenstat_collect_networks' at xenstat_linux.c:306:2:
| xenstat_linux.c:81:6: error: 'strncpy' output may be truncated copying 255
bytes from a string of length 255 [-Werror=stringop-truncation]
| 81 | strncpy(result, de->d_name, resultLen);
| | ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
To solve it, I need to define devBridge[257] as devNoBrideg.
IMHO this is a real compiler error.
de->d_name is an array of 256 bytes, so doing strncpy() from that to
another array of 256 bytes with a length of 256 won't truncate anything.
That's a matter of how you look at it, I think: If the original array
doesn't hold a nul-terminated string, the destination array won't
either, yet the common goal of strncpy() is to yield a properly nul-
terminated string. IOW the warning may be since the standard even has
a specific foot note to point out this possible pitfall.
If the source doesn't hold a nul-terminated string there will still be
256 bytes copied, so there is no truncation done during strncpy().
In fact there is no way to use strncpy() in a safe way on a fixed sized
source array with the above semantics: either the target is larger than
the source and length is at least sizeof(source) + 1, resulting in a
possible read beyond the end of source, or the target is the same length
leading to the error.
Juergen
|
