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

[Laurent Vivier]

Le 30/09/2024 à 15:26, Marc-André Lureau a écrit :

Hi Laurent

On Mon, Sep 30, 2024 at 4:19 PM Laurent Vivier <laur...@vivier.eu> wrote:

CC Helge Deller

Le 30/09/2024 à 10:14, marcandre.lur...@redhat.com a écrit :

From: Marc-André Lureau <marcandre.lur...@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.lur...@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.

That works! I'll change the patch and include your r-b then?

Yes, you can

Thanks,
Laurent