xserver / unit - test hangs when compiled with -Db_ndebug=true (asserts enabled)

When compiled with -Db_ndebug=true (enabling asserts), the xserver / unit test hangs in the cmp_attr_fields function. Without asserts enabled it passes.

This is because the *tags2++ increment happens inside an assert macro:

static void
cmp_attr_fields(InputAttributes * attr1, InputAttributes * attr2)
{
    [...]
    /* check for not sharing memory */
    tags1 = attr1->tags;
    while (*tags1) {
        tags2 = attr2->tags;
        while (*tags2)
            assert(*tags1 != *tags2++);

        tags1++;
    }
}

static void
dix_input_attributes(void)
{
  [...]
  orig->tags = xstrtokenize("tag1 tag2 tag3", " ");
  new = DuplicateInputAttributes(orig);
  cmp_attr_fields(orig, new);
  FreeInputAttributes(new);

  FreeInputAttributes(orig);
}

The test used g_assert until commit 196d679b. I don't know the behavior of g_assert.

Moving the increment outside of the assert causes the test to fail when asserts are disabled:

diff --git a/test/input.c b/test/input.c
index f092bb46d..5e394d2d3 100644
--- a/test/input.c
+++ b/test/input.c
@@ -1173,8 +1173,10 @@ cmp_attr_fields(InputAttributes * attr1, InputAttributes * attr2)
     tags1 = attr1->tags;
     while (*tags1) {
         tags2 = attr2->tags;
-        while (*tags2)
-            assert(*tags1 != *tags2++);
+        while (*tags2) {
+            assert(*tags1 != *tags2);
+            tags2++;
+        }
 
         tags1++;
     }

But I don't know really what the test is doing to debug the failure.

cc: @whot