[PATCH v2 4/7] migration: Rename vmstate_info_nullptr

[Fabiano Rosas]

Rename vmstate_info_nullptr from "uint64_t" to "nullptr". This vmstate
actually reads and writes just a byte, so the proper name would be
uint8. However, since this is a marker for a NULL pointer, it's
convenient to have a more explicit name that can be identified by the
consumers of the JSON part of the stream.

Change the name to "nullptr" and add support for it in the
analyze-migration.py script. Arbitrarily use the name of the type as
the value of the field to avoid the script showing 0x30 or '0', which
could be confusing for readers.

Signed-off-by: Fabiano Rosas <farosas@suse.de>
---
 migration/vmstate-types.c    |  2 +-
 scripts/analyze-migration.py | 22 ++++++++++++++++++++++
 2 files changed, 23 insertions(+), 1 deletion(-)

diff --git a/migration/vmstate-types.c b/migration/vmstate-types.c
index e83bfccb9e..d70d573dbd 100644
--- a/migration/vmstate-types.c
+++ b/migration/vmstate-types.c
@@ -338,7 +338,7 @@ static int put_nullptr(QEMUFile *f, void *pv, size_t size,
 }
 
 const VMStateInfo vmstate_info_nullptr = {
-    .name = "uint64",
+    .name = "nullptr",
     .get  = get_nullptr,
     .put  = put_nullptr,
 };
diff --git a/scripts/analyze-migration.py b/scripts/analyze-migration.py
index fcda11f31d..134c25f20a 100755
--- a/scripts/analyze-migration.py
+++ b/scripts/analyze-migration.py
@@ -377,6 +377,8 @@ def read(self):
 
 
 class VMSDFieldInt(VMSDFieldGeneric):
+    NULL_PTR_MARKER = 0x30
+
     def __init__(self, desc, file):
         super(VMSDFieldInt, self).__init__(desc, file)
         self.size = int(desc['size'])
@@ -385,6 +387,16 @@ def __init__(self, desc, file):
         self.udtype = '>u%d' % self.size
 
     def __repr__(self):
+
+        # A NULL pointer is encoded in the stream as a '0' to
+        # disambiguate from a mere 0x0 value and avoid consumers
+        # trying to follow the NULL pointer. Displaying '0', 0x30 or
+        # 0x0 when analyzing the JSON debug stream could become
+        # confusing, so use an explicit term instead. The actual value
+        # in the stream was already validated by VMSDFieldNull.
+        if self.data == self.NULL_PTR_MARKER:
+            return "nullptr"
+
         if self.data < 0:
             return ('%s (%d)' % ((self.format % self.udata), self.data))
         else:
@@ -417,6 +429,15 @@ def __init__(self, desc, file):
         super(VMSDFieldIntLE, self).__init__(desc, file)
         self.dtype = '<i%d' % self.size
 
+class VMSDFieldNull(VMSDFieldUInt):
+    def __init__(self, desc, file):
+        super(VMSDFieldUInt, self).__init__(desc, file)
+
+    def read(self):
+        super(VMSDFieldUInt, self).read()
+        assert(self.data == self.NULL_PTR_MARKER)
+        return self.data
+
 class VMSDFieldBool(VMSDFieldGeneric):
     def __init__(self, desc, file):
         super(VMSDFieldBool, self).__init__(desc, file)
@@ -558,6 +579,7 @@ def getDict(self):
     "bitmap" : VMSDFieldGeneric,
     "struct" : VMSDFieldStruct,
     "capability": VMSDFieldCap,
+    "nullptr": VMSDFieldNull,
     "unknown" : VMSDFieldGeneric,
 }
 
-- 
2.35.3