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authorEric Blake <eblake@redhat.com>2015-10-26 16:34:51 -0600
committerMarkus Armbruster <armbru@redhat.com>2015-11-02 08:30:27 +0100
commitf51d8fab44b231aa299d8de24cfdf9ba41ef4a21 (patch)
treed1844c9b206001641e82271484233695138f19b8 /scripts/qapi.py
parent5c5e51a05b567fd48fb155d94ca6f7679dd0d478 (diff)
qapi: Start converting to new qapi union layout
We have two issues with our qapi union layout: 1) Even though the QMP wire format spells the tag 'type', the C code spells it 'kind', requiring some hacks in the generator. 2) The C struct uses an anonymous union, which places all tag values in the same namespace as all non-variant members. This leads to spurious collisions if a tag value matches a non-variant member's name. This patch is the front end for a series that converts to a saner qapi union layout. By the end of the series, we will no longer have the type/kind mismatch, and all tag values will be under a named union, which requires clients to access 'obj->u.value' instead of 'obj->value'. But since the conversion touches a number of files, it is easiest if we temporarily support BOTH layouts simultaneously. Given a simple union qapi type: { 'union':'Foo', 'data': { 'a':'int', 'b':'bool' } } make the following changes in generated qapi-types.h: | struct Foo { |- FooKind kind; |- union { /* union tag is @kind */ |+ union { |+ FooKind kind; |+ FooKind type; |+ }; |+ union { /* union tag is @type */ | void *data; | int64_t a; | bool b; |+ union { /* union tag is @type */ |+ void *data; |+ int64_t a; |+ bool b; |+ } u; | }; | }; Flat unions do not need the anonymous union for the tag member, as we already fixed that to use the member name instead of 'kind' back in commit 0f61af3e. One additional change is needed in qapi.py: check_union() now needs to check for collisions with 'type' in addition to those with 'kind'. Later, when the conversions are complete, we will remove the duplication hacks, and also drop the check_union() restrictions. Note, however, that we do not rename the generated enum, which is still 'FooKind'. A further patch could generate implicit enums as 'FooType', but while the generator already reserved the '*Kind' namespace (commit 4dc2e69), there are already QMP constructs with '*Type' naming, which means changing our reservation namespace would have lots of churn to C code to deal with a forced name change. Signed-off-by: Eric Blake <eblake@redhat.com> Message-Id: <1445898903-12082-13-git-send-email-eblake@redhat.com> [Commit message tweaked slightly] Signed-off-by: Markus Armbruster <armbru@redhat.com>
Diffstat (limited to 'scripts/qapi.py')
-rw-r--r--scripts/qapi.py3
1 files changed, 2 insertions, 1 deletions
diff --git a/scripts/qapi.py b/scripts/qapi.py
index 3ff7b11e61..00a16203df 100644
--- a/scripts/qapi.py
+++ b/scripts/qapi.py
@@ -548,7 +548,8 @@ def check_union(expr, expr_info):
base = expr.get('base')
discriminator = expr.get('discriminator')
members = expr['data']
- values = {'MAX': '(automatic)', 'KIND': '(automatic)'}
+ values = {'MAX': '(automatic)', 'KIND': '(automatic)',
+ 'TYPE': '(automatic)'}
# Two types of unions, determined by discriminator.