Re: base64: gcc-15 compile issue

[Pádraig Brady]

On 21/12/2024 19:58, Jeffrey Walton wrote:
> On Sat, Dec 21, 2024 at 9:45 AM Bruno Haible via Gnulib discussion
> list <bug-gnulib@gnu.org> wrote:
> > Rudi Heitbaum wrote:
> > > When compiling grub-2.12 with gcc-15-20241208 the following line causes
> > > the following error:
> > >
> > > https://git.savannah.gnu.org/cgit/gnulib.git/tree/lib/base64.c#n62
> > >
> > > ../../grub-core/lib/gnulib/base64.c:65:3:
> > >    error: initializer-string for array of 'char' is too long
> > >    [-Werror=unterminated-string-initialization]
> > >
> > >     65 |   "ABCDEFGHIJKLMNOPQRSTUVWXYZabcdefghijklmnopqrstuvwxyz0123456789+/";
> > >        |   ^~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
> >
> > No, this line is not causing an error. This line causes a warning, and
> > it is either your use of CPPFLAGS and CFLAGS or grub's configure.ac which
> > adds '-Werror' and thus turns the warning into an error.
> >
> > Use of -Werror with gnulib is unsupported. We cannot avoid all compiler
> > warnings on all systems, in particular because some warnings are style
> > warnings and opposite warnings exist as well.
> >
> > In this case, the code is perfectly fine: it initializes an array of
> > size 64 with 64 characters. There is no better way to write such an
> > initialization.
>
> The string literal includes the trailing NULL, so the literal is 65
> chars, not 64 char.

C99 supports excluding the NUL, while C++ does not.
So this is fine IMHO and gcc shouldn't be warning about this.
Note if you use a non specific sized array, i.e. char b64c[] = "A..."
then you lose the compiler check if the literal is too long
(though there is no warning if the literal is too short).

cheers,
Pádraig