qapi: Reserve 'u' member name

Now that we have separated union tag values from colliding with
non-variant C names, by naming the union 'u', we should reserve
this name for our use. Note that we want to forbid 'u' even in
a struct with no variants, because it is possible for a future
qemu release to extend QMP in a backwards-compatible manner while
converting from a struct to a flat union. Fortunately, no
existing clients were using this member name. If we ever find
the need for QMP to have a member 'u', we could at that time
relax things, perhaps by having c_name() munge the QMP member to
'q_u'.

Note that we cannot forbid 'u' everywhere (by adding the
rejection code to check_name()), because the existing QKeyCode
enum already uses it; therefore we only reserve it as a struct
type member name.

Backports commit 5e59baf90a72cd25d38a3134edc029f4f022da74 from qemu
This commit is contained in:
Eric Blake 2018-02-19 19:28:46 -05:00 committed by Lioncash
parent a75c85afa0
commit 61ad7b3824
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@ -490,7 +490,7 @@ def check_type(expr_info, source, value, allow_array=False,
for (key, arg) in value.items():
check_name(expr_info, "Member of %s" % source, key,
allow_optional=allow_optional)
if c_name(key, False).startswith('has_'):
if c_name(key, False) == 'u' or c_name(key, False).startswith('has_'):
raise QAPIExprError(expr_info,
"Member of %s uses reserved name '%s'"
% (source, key))