Re: [PATCH 5/5] s390x/tcg: fix format-truncation warning

[Marc-André Lureau]

Hi

On Mon, Mar 28, 2022 at 12:59 PM Thomas Huth <thuth@redhat.com> wrote:
>
> On 28/03/2022 10.47, marcandre.lureau@redhat.com wrote:
> > From: Marc-André Lureau <marcandre.lureau@redhat.com>
> >
> > ../target/s390x/tcg/translate.c: In function ‘s390x_translate_init’:
> > ../target/s390x/tcg/translate.c:224:64: error: ‘%d’ directive output may be 
> > truncated writing between 1 and 11 bytes into a region of size 3 
> > [-Werror=format-truncation=]
> >    224 |         snprintf(cpu_reg_names[i], sizeof(cpu_reg_names[0]), 
> > "r%d", i);
> >        |                                                                ^~
> >
> > Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> > ---
> >   target/s390x/tcg/translate.c | 4 ++--
> >   1 file changed, 2 insertions(+), 2 deletions(-)
> >
> > diff --git a/target/s390x/tcg/translate.c b/target/s390x/tcg/translate.c
> > index 5acfc0ff9b4e..a082342a0424 100644
> > --- a/target/s390x/tcg/translate.c
> > +++ b/target/s390x/tcg/translate.c
> > @@ -199,7 +199,7 @@ static TCGv_i64 regs[16];
> >
> >   void s390x_translate_init(void)
> >   {
> > -    int i;
> > +    size_t i;
> >
> >       psw_addr = tcg_global_mem_new_i64(cpu_env,
> >                                         offsetof(CPUS390XState, psw.addr),
> > @@ -221,7 +221,7 @@ void s390x_translate_init(void)
> >                                      "cc_vr");
> >
> >       for (i = 0; i < 16; i++) {
> > -        snprintf(cpu_reg_names[i], sizeof(cpu_reg_names[0]), "r%d", i);
> > +        snprintf(cpu_reg_names[i], sizeof(cpu_reg_names[0]), "r%zu", i);
>
> The compiler is *really* too stupid to see that i is in the range between 0
> and 16 here??? ... that rather sounds like a compiler bug to me than
> something that we should work-around in the QEMU source code. Considering
> that you're using a x.0 release of GCC, please file a bug against GCC
> instead. If they refuse to fix it for GCC 12.1 or later, we can revisit this
> patch, but currently, I really think this should be fixed in GCC instead.
>

I opened: https://gcc.gnu.org/bugzilla/show_bug.cgi?id=105080

Although I think the "workaround" is simple and would avoid users &
distributions having to add --disable-werror, and possibly miss other
issues.