[PATCH] softmmu/physmem: Hint notifier is not NULL in as_translate_for_iotlb()

["Philippe Mathieu-Daudé" <f4bug@amsat.org>]

When using GCC 10.2 configured with --extra-cflags=-Os, we get:

  softmmu/physmem.c: In function ‘address_space_translate_for_iotlb’:
  softmmu/physmem.c:643:26: error: ‘notifier’ may be used uninitialized in this function [-Werror=maybe-uninitialized]
    643 |         notifier->active = true;
        |                          ^
  softmmu/physmem.c:608:23: note: ‘notifier’ was declared here
    608 |     TCGIOMMUNotifier *notifier;
        |                       ^~~~~~~~

Insert assertions as hint to the compiler that 'notifier' can
not be NULL there.

Signed-off-by: Philippe Mathieu-Daudé <f4bug@amsat.org>
---
Yet another hole in our CI.
---
 softmmu/physmem.c | 3 ++-
 1 file changed, 2 insertions(+), 1 deletion(-)

diff --git a/softmmu/physmem.c b/softmmu/physmem.c
index 6301f4f0a5c..65602ed548e 100644
--- a/softmmu/physmem.c
+++ b/softmmu/physmem.c
@@ -605,7 +605,7 @@ static void tcg_register_iommu_notifier(CPUState *cpu,
      * when the IOMMU tells us the mappings we've cached have changed.
      */
     MemoryRegion *mr = MEMORY_REGION(iommu_mr);
-    TCGIOMMUNotifier *notifier;
+    TCGIOMMUNotifier *notifier = NULL;
     int i;
 
     for (i = 0; i < cpu->iommu_notifiers->len; i++) {
@@ -638,6 +638,7 @@ static void tcg_register_iommu_notifier(CPUState *cpu,
         memory_region_register_iommu_notifier(notifier->mr, &notifier->n,
                                               &error_fatal);
     }
+    assert(notifier != NULL);
 
     if (!notifier->active) {
         notifier->active = true;
-- 
2.26.2