[qemu-xen stable-4.17] async: Suppress GCC13 false positive in aio_bh_poll()

[patchbot@xxxxxxx]

commit ffb451126550b22b43b62fb8731a0d78e3376c03
Author:     Cédric Le Goater <clg@xxxxxxxxxx>
AuthorDate: Thu Apr 20 22:29:39 2023 +0200
Commit:     Anthony PERARD <anthony.perard@xxxxxxxxxx>
CommitDate: Fri Jul 21 11:57:33 2023 +0100

    async: Suppress GCC13 false positive in aio_bh_poll()
    
    GCC13 reports an error :
    
    ../util/async.c: In function â??aio_bh_pollâ??:
    include/qemu/queue.h:303:22: error: storing the address of local variable 
â??sliceâ?? in â??*ctx.bh_slice_list.sqh_lastâ?? [-Werror=dangling-pointer=]
      303 |     (head)->sqh_last = &(elm)->field.sqe_next;                      
    \
          |     ~~~~~~~~~~~~~~~~~^~~~~~~~~~~~~~~~~~~~~~~~
    ../util/async.c:169:5: note: in expansion of macro 
â??QSIMPLEQ_INSERT_TAILâ??
      169 |     QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
          |     ^~~~~~~~~~~~~~~~~~~~
    ../util/async.c:161:17: note: â??sliceâ?? declared here
      161 |     BHListSlice slice;
          |                 ^~~~~
    ../util/async.c:161:17: note: â??ctxâ?? declared here
    
    But the local variable 'slice' is removed from the global context list
    in following loop of the same routine. Add a pragma to silent GCC.
    
    Cc: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    Cc: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    Cc: Daniel P. Berrangé <berrange@xxxxxxxxxx>
    Signed-off-by: Cédric Le Goater <clg@xxxxxxxxxx>
    Reviewed-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>
    Reviewed-by: Philippe Mathieu-Daudé <philmd@xxxxxxxxxx>
    Reviewed-by: Stefan Hajnoczi <stefanha@xxxxxxxxxx>
    Reviewed-by: Thomas Huth <thuth@xxxxxxxxxx>
    Tested-by: Daniel Henrique Barboza <danielhb413@xxxxxxxxx>
    Message-Id: <20230420202939.1982044-1-clg@xxxxxxxx>
    Signed-off-by: Paolo Bonzini <pbonzini@xxxxxxxxxx>
    (cherry picked from commit d66ba6dc1cce914673bd8a89fca30a7715ea70d1)
---
 util/async.c | 14 ++++++++++++++
 1 file changed, 14 insertions(+)

diff --git a/util/async.c b/util/async.c
index 2ea1172f3e..0b3bf38e9d 100644
--- a/util/async.c
+++ b/util/async.c
@@ -150,7 +150,21 @@ int aio_bh_poll(AioContext *ctx)
     int ret = 0;
 
     QSLIST_MOVE_ATOMIC(&slice.bh_list, &ctx->bh_list);
+
+    /*
+     * GCC13 [-Werror=dangling-pointer=] complains that the local variable
+     * 'slice' is being stored in the global 'ctx->bh_slice_list' but the
+     * list is emptied before this function returns.
+     */
+#if !defined(__clang__)
+#pragma GCC diagnostic push
+#pragma GCC diagnostic ignored "-Wpragmas"
+#pragma GCC diagnostic ignored "-Wdangling-pointer="
+#endif
     QSIMPLEQ_INSERT_TAIL(&ctx->bh_slice_list, &slice, next);
+#if !defined(__clang__)
+#pragma GCC diagnostic pop
+#endif
 
     while ((s = QSIMPLEQ_FIRST(&ctx->bh_slice_list))) {
         QEMUBH *bh;
--
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