qapi-visit: Fix generated code when schema has forward refs

The visit_type_implicit_FOO() are generated on demand, right before
their first use.  Used by visit_type_STRUCT_fields() when STRUCT has
base FOO, and by visit_type_UNION() when flat UNION has member a FOO.

If the schema defines FOO after its first use as struct base or flat
union member, visit_type_implicit_FOO() calls
visit_type_implicit_FOO() before its definition, which doesn't
compile.

Rearrange qapi-schema-test.json to demonstrate the bug.

Fix by generating the necessary forward declaration.

Signed-off-by: Markus Armbruster <armbru@redhat.com>
Reviewed-by: Eric Blake <eblake@redhat.com>

1 files changed, 17 insertions, 13 deletions

diff --git a/tests/qapi-schema/qapi-schema-test.json b/tests/qapi-schema/qapi-schema-test.json
index c7eaa865da..ccadb13785 100644
--- a/tests/qapi-schema/qapi-schema-test.json
+++ b/tests/qapi-schema/qapi-schema-test.json
@@ -7,13 +7,13 @@
   'data': { 'enum1': 'EnumOne', '*enum2': 'EnumOne', 'enum3': 'EnumOne', '*enum4': 'EnumOne' } }
 
 # for testing nested structs
-{ 'struct': 'UserDefZero',
-  'data': { 'integer': 'int' } }
-
 { 'struct': 'UserDefOne',
-  'base': 'UserDefZero',
+  'base': 'UserDefZero',        # intentional forward reference
   'data': { 'string': 'str', '*enum1': 'EnumOne' } }
 
+{ 'struct': 'UserDefZero',
+  'data': { 'integer': 'int' } }
+
 { 'struct': 'UserDefTwoDictDict',
   'data': { 'userdef': 'UserDefOne', 'string': 'str' } }
 
@@ -33,29 +33,33 @@
 { 'struct': 'UserDefB',
   'data': { 'integer': 'int' } }
 
-{ 'struct': 'UserDefC',
-  'data': { 'string1': 'str', 'string2': 'str' } }
-
-{ 'struct': 'UserDefUnionBase',
-  'data': { 'string': 'str', 'enum1': 'EnumOne' } }
-
 { 'union': 'UserDefFlatUnion',
-  'base': 'UserDefUnionBase',
+  'base': 'UserDefUnionBase',   # intentional forward reference
   'discriminator': 'enum1',
-  'data': { 'value1' : 'UserDefA', 'value2' : 'UserDefB', 'value3' : 'UserDefB' } }
+  'data': { 'value1' : 'UserDefA',
+            'value2' : 'UserDefB',
+            'value3' : 'UserDefB' } }
 # FIXME generated struct UserDefFlatUnion has members for direct base
 # UserDefOne, but lacks members for indirect base UserDefZero
 
+{ 'struct': 'UserDefUnionBase',
+  'data': { 'string': 'str', 'enum1': 'EnumOne' } }
+
 # this variant of UserDefFlatUnion defaults to a union that uses fields with
 # allocated types to test corner cases in the cleanup/dealloc visitor
 { 'union': 'UserDefFlatUnion2',
   'base': 'UserDefUnionBase',
   'discriminator': 'enum1',
-  'data': { 'value1' : 'UserDefC', 'value2' : 'UserDefB', 'value3' : 'UserDefA' } }
+  'data': { 'value1' : 'UserDefC', # intentional forward reference
+            'value2' : 'UserDefB',
+            'value3' : 'UserDefA' } }
 
 { 'alternate': 'UserDefAlternate',
   'data': { 'uda': 'UserDefA', 's': 'str', 'i': 'int' } }
 
+{ 'struct': 'UserDefC',
+  'data': { 'string1': 'str', 'string2': 'str' } }
+
 # for testing native lists
 { 'union': 'UserDefNativeListUnion',
   'data': { 'integer': ['int'],