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[Qemu-devel] [PATCH v5 37/46] qapi: Forbid empty unions and useless alte
From: |
Eric Blake |
Subject: |
[Qemu-devel] [PATCH v5 37/46] qapi: Forbid empty unions and useless alternates |
Date: |
Mon, 21 Sep 2015 15:57:53 -0600 |
Empty unions serve no purpose, and while we compile with gcc
which permits them, strict C99 forbids them. We could inject
a dummy member (and in fact, we do for empty structs), but while
empty structs make sense in qapi, empty unions don't add any
expressiveness to the QMP language. So prohibit them at parse
time. Update the documentation and testsuite to match.
Signed-off-by: Eric Blake <address@hidden>
---
docs/qapi-code-gen.txt | 15 ++++++++-------
scripts/qapi.py | 12 ++++++++++--
tests/qapi-schema/alternate-empty.err | 1 +
tests/qapi-schema/alternate-empty.exit | 2 +-
tests/qapi-schema/alternate-empty.json | 2 +-
tests/qapi-schema/alternate-empty.out | 3 ---
tests/qapi-schema/flat-union-empty.err | 1 +
tests/qapi-schema/flat-union-empty.exit | 2 +-
tests/qapi-schema/flat-union-empty.json | 2 +-
tests/qapi-schema/flat-union-empty.out | 7 -------
tests/qapi-schema/union-empty.err | 1 +
tests/qapi-schema/union-empty.exit | 2 +-
tests/qapi-schema/union-empty.json | 2 +-
tests/qapi-schema/union-empty.out | 4 ----
14 files changed, 27 insertions(+), 29 deletions(-)
diff --git a/docs/qapi-code-gen.txt b/docs/qapi-code-gen.txt
index 842be1b..f0fb881 100644
--- a/docs/qapi-code-gen.txt
+++ b/docs/qapi-code-gen.txt
@@ -182,11 +182,11 @@ prevent incomplete include files.
Usage: { 'struct': STRING, 'data': DICT, '*base': STRUCT-NAME }
-A struct is a dictionary containing a single 'data' key whose
-value is a dictionary. This corresponds to a struct in C or an Object
-in JSON. Each value of the 'data' dictionary must be the name of a
-type, or a one-element array containing a type name. An example of a
-struct is:
+A struct is a dictionary containing a single 'data' key whose value is
+a dictionary; the dictionary may be empty. This corresponds to a
+struct in C or an Object in JSON. Each value of the 'data' dictionary
+must be the name of a type, or a one-element array containing a type
+name. An example of a struct is:
{ 'struct': 'MyType',
'data': { 'member1': 'str', 'member2': 'int', '*member3': 'str' } }
@@ -283,9 +283,10 @@ or: { 'union': STRING, 'data': DICT, 'base':
STRUCT-NAME,
Union types are used to let the user choose between several different
variants for an object. There are two flavors: simple (no
-discriminator or base), flat (both discriminator and base). A union
+discriminator or base), and flat (both discriminator and base). A union
type is defined using a data dictionary as explained in the following
-paragraphs.
+paragraphs. The data dictionary for either type of union must not
+be empty.
A simple union type defines a mapping from automatic discriminator
values to data types like in this example:
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 18cfde1..a93053d 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -573,7 +573,10 @@ def check_union(expr, expr_info):
"Discriminator '%s' must be of enumeration "
"type" % discriminator)
- # Check every branch
+ # Check every branch; don't allow an empty union
+ if len(members) == 0:
+ raise QAPIExprError(expr_info,
+ "Union '%s' cannot have empty 'data'" % name)
for (key, value) in members.items():
check_name(expr_info, "Member of union '%s'" % name, key)
@@ -606,7 +609,11 @@ def check_alternate(expr, expr_info):
values = {'MAX': '(automatic)'}
types_seen = {}
- # Check every branch
+ # Check every branch; require at least two branches
+ if len(members) < 2:
+ raise QAPIExprError(expr_info,
+ "Alternate '%s' should have at least two branches "
+ "in 'data'" % name)
for (key, value) in members.items():
check_name(expr_info, "Member of alternate '%s'" % name, key)
@@ -1013,6 +1020,7 @@ class QAPISchemaObjectTypeVariants(object):
def __init__(self, tag_name, tag_enum, variants):
assert tag_name is None or isinstance(tag_name, str)
assert tag_enum is None or isinstance(tag_enum, str)
+ assert len(variants) > 0
for v in variants:
assert isinstance(v, QAPISchemaObjectTypeVariant)
self._tag_name = tag_name
diff --git a/tests/qapi-schema/alternate-empty.err
b/tests/qapi-schema/alternate-empty.err
index e69de29..bb06c5b 100644
--- a/tests/qapi-schema/alternate-empty.err
+++ b/tests/qapi-schema/alternate-empty.err
@@ -0,0 +1 @@
+tests/qapi-schema/alternate-empty.json:2: Alternate 'Alt' should have at least
two branches in 'data'
diff --git a/tests/qapi-schema/alternate-empty.exit
b/tests/qapi-schema/alternate-empty.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/alternate-empty.exit
+++ b/tests/qapi-schema/alternate-empty.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/alternate-empty.json
b/tests/qapi-schema/alternate-empty.json
index db3820f..fff15ba 100644
--- a/tests/qapi-schema/alternate-empty.json
+++ b/tests/qapi-schema/alternate-empty.json
@@ -1,2 +1,2 @@
-# FIXME - alternates should list at least two types to be useful
+# alternates must list at least two types to be useful
{ 'alternate': 'Alt', 'data': { 'i': 'int' } }
diff --git a/tests/qapi-schema/alternate-empty.out
b/tests/qapi-schema/alternate-empty.out
index 9b010d8..e69de29 100644
--- a/tests/qapi-schema/alternate-empty.out
+++ b/tests/qapi-schema/alternate-empty.out
@@ -1,3 +0,0 @@
-object :empty
-alternate Alt
- case i: int
diff --git a/tests/qapi-schema/flat-union-empty.err
b/tests/qapi-schema/flat-union-empty.err
index e69de29..15754f5 100644
--- a/tests/qapi-schema/flat-union-empty.err
+++ b/tests/qapi-schema/flat-union-empty.err
@@ -0,0 +1 @@
+tests/qapi-schema/flat-union-empty.json:4: Union 'Union' cannot have empty
'data'
diff --git a/tests/qapi-schema/flat-union-empty.exit
b/tests/qapi-schema/flat-union-empty.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/flat-union-empty.exit
+++ b/tests/qapi-schema/flat-union-empty.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/flat-union-empty.json
b/tests/qapi-schema/flat-union-empty.json
index 67dd297..77f1d9a 100644
--- a/tests/qapi-schema/flat-union-empty.json
+++ b/tests/qapi-schema/flat-union-empty.json
@@ -1,4 +1,4 @@
-# FIXME - flat unions should not be empty
+# flat unions cannot be empty
{ 'enum': 'Empty', 'data': [ ] }
{ 'struct': 'Base', 'data': { 'type': 'Empty' } }
{ 'union': 'Union', 'base': 'Base', 'discriminator': 'type', 'data': { } }
diff --git a/tests/qapi-schema/flat-union-empty.out
b/tests/qapi-schema/flat-union-empty.out
index 0e0665a..e69de29 100644
--- a/tests/qapi-schema/flat-union-empty.out
+++ b/tests/qapi-schema/flat-union-empty.out
@@ -1,7 +0,0 @@
-object :empty
-object Base
- member type: Empty optional=False
-enum Empty []
-object Union
- base Base
- tag type
diff --git a/tests/qapi-schema/union-empty.err
b/tests/qapi-schema/union-empty.err
index e69de29..12c2022 100644
--- a/tests/qapi-schema/union-empty.err
+++ b/tests/qapi-schema/union-empty.err
@@ -0,0 +1 @@
+tests/qapi-schema/union-empty.json:2: Union 'Union' cannot have empty 'data'
diff --git a/tests/qapi-schema/union-empty.exit
b/tests/qapi-schema/union-empty.exit
index 573541a..d00491f 100644
--- a/tests/qapi-schema/union-empty.exit
+++ b/tests/qapi-schema/union-empty.exit
@@ -1 +1 @@
-0
+1
diff --git a/tests/qapi-schema/union-empty.json
b/tests/qapi-schema/union-empty.json
index 1785007..1f0b13c 100644
--- a/tests/qapi-schema/union-empty.json
+++ b/tests/qapi-schema/union-empty.json
@@ -1,2 +1,2 @@
-# FIXME - unions should not be empty
+# unions cannot be empty
{ 'union': 'Union', 'data': { } }
diff --git a/tests/qapi-schema/union-empty.out
b/tests/qapi-schema/union-empty.out
index c5500da..e69de29 100644
--- a/tests/qapi-schema/union-empty.out
+++ b/tests/qapi-schema/union-empty.out
@@ -1,4 +0,0 @@
-object :empty
-object Union
- tag type
-enum UnionKind []
--
2.4.3
- [Qemu-devel] [PATCH v5 28/46] qapi: Rework deallocation of partial struct, (continued)
- [Qemu-devel] [PATCH v5 28/46] qapi: Rework deallocation of partial struct, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 29/46] qapi: Change visit_type_FOO() to no longer return partial objects, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 30/46] net: use Netdev instead of NetClientOptions in client init, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 33/46] vnc: hoist allocation of VncBasicInfo to callers, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 32/46] qapi: Hide tag_name data member of variants, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 35/46] qapi-visit: Remove redundant functions for flat union base, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 34/46] qapi: Unbox base members, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 36/46] qapi: Avoid use of 'data' member of qapi unions, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 38/46] qapi: Drop useless 'data' member of unions, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 37/46] qapi: Forbid empty unions and useless alternates,
Eric Blake <=
- [Qemu-devel] [PATCH v5 39/46] qapi: Plumb in 'box' to qapi generator lower levels, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 41/46] qapi: Support boxed unions, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 40/46] qapi: Implement boxed structs for commands/events, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 42/46] qapi: support implicit structs in OptsVisitor, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 31/46] qapi: use 'type' in generated C code to match QMP union wire form, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 44/46] net: Use correct type for bool flag, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 46/46] qapi: Allow anonymous base for flat union, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 43/46] qapi: Change Netdev into a flat union, Eric Blake, 2015/09/21
- [Qemu-devel] [PATCH v5 45/46] net: Complete qapi-fication of netdev_add, Eric Blake, 2015/09/21