Re: [PATCH v3 15/22] linux-user/hppa: fix -Werror=maybe-uninitialized false-positive

[Laurent Vivier <laurent@vivier.eu>]

CC Helge Deller

Le 30/09/2024 à 10:14, marcandre.lureau@redhat.com a écrit :
> From: Marc-André Lureau <marcandre.lureau@redhat.com>
> 
> ../linux-user/hppa/cpu_loop.c: In function ‘hppa_lws’:
> ../linux-user/hppa/cpu_loop.c:106:17: error: ‘ret’ may be used uninitialized [-Werror=maybe-uninitialized]
>    106 |     env->gr[28] = ret;
> 
> Signed-off-by: Marc-André Lureau <marcandre.lureau@redhat.com>
> ---
>   linux-user/hppa/cpu_loop.c | 10 +++++-----
>   1 file changed, 5 insertions(+), 5 deletions(-)
> 
> diff --git a/linux-user/hppa/cpu_loop.c b/linux-user/hppa/cpu_loop.c
> index bc093b8fe8..f4da95490e 100644
> --- a/linux-user/hppa/cpu_loop.c
> +++ b/linux-user/hppa/cpu_loop.c
> @@ -43,7 +43,7 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
>           old = tswap32(old);
>           new = tswap32(new);
>           ret = qatomic_cmpxchg((uint32_t *)g2h(cs, addr), old, new);
> -        ret = tswap32(ret);
> +        env->gr[28] = tswap32(ret);
>           break;
>   
>       case 2: /* elf32 atomic "new" cmpxchg */
> @@ -64,19 +64,19 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
>               old = *(uint8_t *)g2h(cs, old);
>               new = *(uint8_t *)g2h(cs, new);
>               ret = qatomic_cmpxchg((uint8_t *)g2h(cs, addr), old, new);
> -            ret = ret != old;
> +            env->gr[28] = ret != old;
>               break;
>           case 1:
>               old = *(uint16_t *)g2h(cs, old);
>               new = *(uint16_t *)g2h(cs, new);
>               ret = qatomic_cmpxchg((uint16_t *)g2h(cs, addr), old, new);
> -            ret = ret != old;
> +            env->gr[28] = ret != old;
>               break;
>           case 2:
>               old = *(uint32_t *)g2h(cs, old);
>               new = *(uint32_t *)g2h(cs, new);
>               ret = qatomic_cmpxchg((uint32_t *)g2h(cs, addr), old, new);
> -            ret = ret != old;
> +            env->gr[28] = ret != old;
>               break;
>           case 3:
>               {
> @@ -97,13 +97,13 @@ static abi_ulong hppa_lws(CPUHPPAState *env)
>                   }
>                   end_exclusive();
>   #endif
> +                env->gr[28] = ret;
>               }
>               break;
>           }
>           break;
>       }
>   
> -    env->gr[28] = ret;
>       return 0;
>   }
>   

Did you try to put a g_assert_not_reached() in a "default:" for "switch(size)"?
This should help the compiler to know that "env->gr[28] = ret;" will not be reached if ret is not set.

Thanks,
Laurent