From bac5429ccb4f41d421ec641b11f1852c8420fdb7 Mon Sep 17 00:00:00 2001 From: Eric Blake Date: Tue, 1 Dec 2015 22:20:59 -0700 Subject: [PATCH] qapi: Detect base class loops It should be fairly obvious that qapi base classes need to form an acyclic graph, since QMP cannot specify the same key more than once, while base classes are included as flat members alongside other members added by the child. But the old check_member_clash() parser function was not prepared to check for this, and entered an infinite recursion (at least until Python gives up, complaining about nesting too deep). Now that check_member_clash() has been recently removed, attempts at self-inheritance trigger an assertion failure introduced by commit ac88219a. The obvious fix is to turn the assertion into a conditional. This patch includes both the tests (base-cycle-direct and base-cycle-indirect) and the fix, since the .err file output for the unfixed case is not useful (particularly when it was warning about unbounded recursion, as that limit may be platform-specific). We don't need to worry about cycles in flat unions (neither the base type nor the type of a variant can be a union) nor in alternates (alternate branches cannot themselves be an alternate). But if we later allow a union type as a variant, we will still be okay, as QAPISchemaObjectTypeVariants.check() triggers the same QAPISchemaObjectType.check() that will detect any loops. Likewise, we need not worry about the case of diamond inheritance where the same class is used for a flat union base class and one of its variants; either both uses will introduce a collision in trying to insert the same member name twice, or the shared type is empty and changes nothing. Signed-off-by: Eric Blake Message-Id: <1449033659-25497-16-git-send-email-eblake@redhat.com> Signed-off-by: Markus Armbruster --- scripts/qapi.py | 4 +++- tests/Makefile | 2 ++ tests/qapi-schema/base-cycle-direct.err | 1 + tests/qapi-schema/base-cycle-direct.exit | 1 + tests/qapi-schema/base-cycle-direct.json | 2 ++ tests/qapi-schema/base-cycle-direct.out | 0 tests/qapi-schema/base-cycle-indirect.err | 1 + tests/qapi-schema/base-cycle-indirect.exit | 1 + tests/qapi-schema/base-cycle-indirect.json | 3 +++ tests/qapi-schema/base-cycle-indirect.out | 0 10 files changed, 14 insertions(+), 1 deletion(-) create mode 100644 tests/qapi-schema/base-cycle-direct.err create mode 100644 tests/qapi-schema/base-cycle-direct.exit create mode 100644 tests/qapi-schema/base-cycle-direct.json create mode 100644 tests/qapi-schema/base-cycle-direct.out create mode 100644 tests/qapi-schema/base-cycle-indirect.err create mode 100644 tests/qapi-schema/base-cycle-indirect.exit create mode 100644 tests/qapi-schema/base-cycle-indirect.json create mode 100644 tests/qapi-schema/base-cycle-indirect.out diff --git a/scripts/qapi.py b/scripts/qapi.py index 8edfd79c52..7dec611d09 100644 --- a/scripts/qapi.py +++ b/scripts/qapi.py @@ -940,7 +940,9 @@ class QAPISchemaObjectType(QAPISchemaType): self.members = None def check(self, schema): - assert self.members is not False # not running in cycles + if self.members is False: # check for cycles + raise QAPIExprError(self.info, + "Object %s contains itself" % self.name) if self.members: return self.members = False # mark as being checked diff --git a/tests/Makefile b/tests/Makefile index 69cef7760d..053c1ae481 100644 --- a/tests/Makefile +++ b/tests/Makefile @@ -257,6 +257,8 @@ qapi-schema += bad-ident.json qapi-schema += bad-type-bool.json qapi-schema += bad-type-dict.json qapi-schema += bad-type-int.json +qapi-schema += base-cycle-direct.json +qapi-schema += base-cycle-indirect.json qapi-schema += command-int.json qapi-schema += comments.json qapi-schema += double-data.json diff --git a/tests/qapi-schema/base-cycle-direct.err b/tests/qapi-schema/base-cycle-direct.err new file mode 100644 index 0000000000..9c68f6543d --- /dev/null +++ b/tests/qapi-schema/base-cycle-direct.err @@ -0,0 +1 @@ +tests/qapi-schema/base-cycle-direct.json:2: Object Loopy contains itself diff --git a/tests/qapi-schema/base-cycle-direct.exit b/tests/qapi-schema/base-cycle-direct.exit new file mode 100644 index 0000000000..d00491fd7e --- /dev/null +++ b/tests/qapi-schema/base-cycle-direct.exit @@ -0,0 +1 @@ +1 diff --git a/tests/qapi-schema/base-cycle-direct.json b/tests/qapi-schema/base-cycle-direct.json new file mode 100644 index 0000000000..4fc66d0516 --- /dev/null +++ b/tests/qapi-schema/base-cycle-direct.json @@ -0,0 +1,2 @@ +# we reject a loop in base classes +{ 'struct': 'Loopy', 'base': 'Loopy', 'data': {} } diff --git a/tests/qapi-schema/base-cycle-direct.out b/tests/qapi-schema/base-cycle-direct.out new file mode 100644 index 0000000000..e69de29bb2 diff --git a/tests/qapi-schema/base-cycle-indirect.err b/tests/qapi-schema/base-cycle-indirect.err new file mode 100644 index 0000000000..fc92fe47f8 --- /dev/null +++ b/tests/qapi-schema/base-cycle-indirect.err @@ -0,0 +1 @@ +tests/qapi-schema/base-cycle-indirect.json:2: Object Base1 contains itself diff --git a/tests/qapi-schema/base-cycle-indirect.exit b/tests/qapi-schema/base-cycle-indirect.exit new file mode 100644 index 0000000000..d00491fd7e --- /dev/null +++ b/tests/qapi-schema/base-cycle-indirect.exit @@ -0,0 +1 @@ +1 diff --git a/tests/qapi-schema/base-cycle-indirect.json b/tests/qapi-schema/base-cycle-indirect.json new file mode 100644 index 0000000000..28667721a3 --- /dev/null +++ b/tests/qapi-schema/base-cycle-indirect.json @@ -0,0 +1,3 @@ +# we reject a loop in base classes +{ 'struct': 'Base1', 'base': 'Base2', 'data': {} } +{ 'struct': 'Base2', 'base': 'Base1', 'data': {} } diff --git a/tests/qapi-schema/base-cycle-indirect.out b/tests/qapi-schema/base-cycle-indirect.out new file mode 100644 index 0000000000..e69de29bb2