Re: New Tot Build problem with Tot GCC (strncpy warnings)

[Joseph Myers <joseph at codesourcery dot com>]

On Tue, 12 Dec 2017, Steve Ellcey wrote:

> I am not sure if this is due to a GCC change or a glibc change but I am
> still unable to build the ToT glibc with the ToT GCC.  The
> nextafter/nexttoward problem has been fixed, the current errors I get
> are due to strncpy warnings.  I thought we had fixed these but either
> GCC changed or glibc changed and we have some new ones:
> 
> Building glibc on aarch64:
> 
> In file included from nss_files/files-init.c:22:
> nss_files/files-init.c: In function ‘_nss_files_init’:
> ../nscd/nscd.h:111:8: error: ‘strncpy’ output truncated copying 4 bytes
> from a string of length 11 [-Werror=stringop-truncation]
>         strncpy (file->dname, file->fname, len);
>         ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

These look like they should be memcpy.  The truncation is intended (it's 
copying a directory name without the trailing '/' and filename in the 
source string), but since the exact amount to copy is known at that point, 
memcpy suffices to express the intent and should avoid the warning.

-- 
Joseph S. Myers
joseph@codesourcery.com