[PULL 7/8] meson: document why we don't generate trace events for tests/ and qga/

[Markus Armbruster <armbru@redhat.com>]

From: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>

Making trace generation work for tests/ and qga/ would involve some
Meson hackery to ensure we generate the trace-events files before
trace-tool uses them. Since we don't actually support tracing there
anyway, we bypass that problem.

Let's add corresponding comments.

Signed-off-by: Vladimir Sementsov-Ogievskiy <vsementsov@virtuozzo.com>
Message-Id: <20220126161130.3240892-7-vsementsov@virtuozzo.com>
Reviewed-by: Stefan Hajnoczi <stefanha@redhat.com>
Reviewed-by: Markus Armbruster <armbru@redhat.com>
[Pasto fixed, commit message punctuation tidied up]
Signed-off-by: Markus Armbruster <armbru@redhat.com>
---
 qga/meson.build   | 7 +++++++
 tests/meson.build | 7 +++++++
 2 files changed, 14 insertions(+)

diff --git a/qga/meson.build b/qga/meson.build
index cfb1fbc085..724d5a667b 100644
--- a/qga/meson.build
+++ b/qga/meson.build
@@ -15,6 +15,13 @@ qga_qapi_outputs = [
   'qga-qapi-visit.h',
 ]
 
+# Problem: to generate trace events, we'd have to add the .trace-events
+# file to qapi_trace_events like we do in qapi/meson.build.  Since
+# qapi_trace_events is used by trace/meson.build, we'd have to move
+# subdir('qga') above subdir('trace') in the top-level meson.build.
+# Can't, because it would break the dependency of qga on qemuutil (which
+# depends on trace_ss).  Not worth solving now; simply suppress trace
+# event generation instead.
 qga_qapi_files = custom_target('QGA QAPI files',
                                output: qga_qapi_outputs,
                                input: 'qapi-schema.json',
diff --git a/tests/meson.build b/tests/meson.build
index 3f3882748a..c8ab6272d1 100644
--- a/tests/meson.build
+++ b/tests/meson.build
@@ -31,6 +31,13 @@ test_qapi_outputs = [
   'test-qapi-visit.h',
 ]
 
+# Problem: to generate trace events, we'd have to add the .trace-events
+# file to qapi_trace_events like we do in qapi/meson.build.  Since
+# qapi_trace_events is used by trace/meson.build, we'd have to move
+# subdir('tests') above subdir('trace') in the top-level meson.build.
+# Can't, because it would break the dependency of qga on qemuutil (which
+# depends on trace_ss).  Not worth solving now; simply suppress trace
+# event generation instead.
 test_qapi_files = custom_target('Test QAPI files',
                                 output: test_qapi_outputs,
                                 input: files('qapi-schema/qapi-schema-test.json',
-- 
2.31.1