Merge remote-tracking branch 'remotes/armbru/tags/pull-qapi-2018-07-03' into staging

QAPI patches for 2018-07-03

# gpg: Signature made Tue 03 Jul 2018 21:52:55 BST
# gpg:                using RSA key 3870B400EB918653
# gpg: Good signature from "Markus Armbruster <armbru@redhat.com>"
# gpg:                 aka "Markus Armbruster <armbru@pond.sub.org>"
# Primary key fingerprint: 354B C8B3 D7EB 2A6B 6867  4E5F 3870 B400 EB91 8653

* remotes/armbru/tags/pull-qapi-2018-07-03:
  qapi: add conditions to SPICE type/commands/events on the schema
  qapi: add conditions to VNC type/commands/events on the schema
  qapi: add 'If:' section to generated documentation
  qapi-types: add #if conditions to types & visitors
  qapi/events: add #if conditions to events
  qapi/commands: add #if conditions to commands
  qapi-introspect: add preprocessor conditions to generated QLit
  qapi-introspect: modify to_qlit() to append ',' on level > 0
  qapi: add #if/#endif helpers
  qapi: mcgen() shouldn't indent # lines
  qapi: add 'ifcond' to visitor methods
  qapi: leave the ifcond attribute undefined until check()
  qapi: pass 'if' condition into QAPISchemaEntity objects
  qapi: add 'if' to top-level expressions

Signed-off-by: Peter Maydell <peter.maydell@linaro.org>

1 files changed, 29 insertions, 0 deletions

diff --git a/docs/devel/qapi-code-gen.txt b/docs/devel/qapi-code-gen.txt
index 94a7e8f4d0..d3b0990983 100644
--- a/docs/devel/qapi-code-gen.txt
+++ b/docs/devel/qapi-code-gen.txt
@@ -744,6 +744,35 @@ Example: Red Hat, Inc. controls redhat.com, and may therefore add a
 downstream command __com.redhat_drive-mirror.
 
 
+=== Configuring the schema ===
+
+The 'struct', 'enum', 'union', 'alternate', 'command' and 'event'
+top-level expressions can take an 'if' key.  Its value must be a string
+or a list of strings.  A string is shorthand for a list containing just
+that string.  The code generated for the top-level expression will then
+be guarded by #if COND for each COND in the list.
+
+Example: a conditional struct
+
+ { 'struct': 'IfStruct', 'data': { 'foo': 'int' },
+   'if': ['defined(CONFIG_FOO)', 'defined(HAVE_BAR)'] }
+
+gets its generated code guarded like this:
+
+ #if defined(CONFIG_FOO)
+ #if defined(HAVE_BAR)
+ ... generated code ...
+ #endif /* defined(HAVE_BAR) */
+ #endif /* defined(CONFIG_FOO) */
+
+Please note that you are responsible to ensure that the C code will
+compile with an arbitrary combination of conditions, since the
+generators are unable to check it at this point.
+
+The presence of 'if' keys in the schema is reflected through to the
+introspection output depending on the build configuration.
+
+
 == Client JSON Protocol introspection ==
 
 Clients of a Client JSON Protocol commonly need to figure out what