Percetto is using designated struct initializers, but those are not
supported in standard C++ before C++20, resulting in some compilation
warnings.
The previous fix for that was using a diagnostic valid for clang but not
for g++ resulting in another warning when building with g++:
-----------------------------------------------------------------------
In file included from ../monado/src/xrt/auxiliary/math/m_relation_history.cpp:19:
../monado/src/xrt/auxiliary/util/u_trace_marker.h:21:32: warning: unknown option after ‘#pragma GCC diagnostic’ kind [-Wpragmas]
21 | #pragma GCC diagnostic ignored "-Wc99-designator"
| ^~~~~~~~~~~~~~~~~~
-----------------------------------------------------------------------
For GCC the diagnostics to disable is actually "-Wpedantic", as shown
below:
-----------------------------------------------------------------------
In file included from ../monado/src/xrt/auxiliary/util/u_trace_marker.h:25,
from ../monado/src/xrt/auxiliary/math/m_relation_history.cpp:19:
../external/percetto/src/percetto.h: In function ‘void percetto_event_with_args(percetto_category*, uint32_t, const char*, int32_t, const percetto_track*, int64_t, uint64_t)’:
../external/percetto/src/percetto.h:424:5: warning: C++ designated initializers only available with ‘-std=c++2a’ or ‘-std=gnu++2a’ [-Wpedantic]
424 | .track = track,
| ^
-----------------------------------------------------------------------
And for clang "-Wc++20-designator" should be slightly more accurate:
-----------------------------------------------------------------------
In file included from ../monado/src/xrt/auxiliary/util/u_trace_marker.h:29:
../external/percetto/src/percetto.h:424:5: warning: designated initializers are a C++20 extension [-Wc++20-designator]
.track = track,
^
-----------------------------------------------------------------------
Fix all the warnings by ignoring the right diagnostics depending on the
compiler, taking care of differentiating clang++ from g++ as they both
define __GNUC__.
Should a application load and unload the OpenXR runtime driver multiple times
the Perfetto code becomes unstable and eventually crashes. This unfortunately
happens with the CTS, to avoid having to recompile Monado and a env variable
to control if tracing should be used.
Only the camera tracking config writes and uses the version field.
Unfortunately the tracking override config is written into the same json
object while not making use of the version field.
If the last returned display time shifts backwards slightly with respect to the
last sampled display time from the compositor, the next predicted display time
will not move forward by one frame. Adding half the display period to the
comparison makes the pacing robust to this case.
Add some missing returns pointed out by -Wreturn-type:
-----------------------------------------------------------------------
[75/1571] Building C object src/xrt/auxiliary/CMakeFiles/aux_util.dir/util/u_config_json.c.o
.../src/xrt/auxiliary/util/u_config_json.c: In function ‘u_gui_state_scene_to_string’:
.../src/xrt/auxiliary/util/u_config_json.c:524:1: warning: control reaches end of non-void function [-Wreturn-type]
524 | }
| ^
-----------------------------------------------------------------------
Some variables are only used in asserts, so they may be unused
depending on the build type:
-----------------------------------------------------------------------
[68/315] Building C object src/xrt/auxiliary/CMakeFiles/aux_util.dir/util/u_sink_combiner.c.o
.../src/xrt/auxiliary/util/u_sink_combiner.c:188:11: warning: unused variable 'diff_ns' [-Wunused-variable]
int64_t diff_ns = frames[0]->timestamp - frames[1]->timestamp;
^
1 warning generated.
[205/315] Building C object src/xrt/compositor/CMakeFiles/comp_main.dir/main/comp_renderer.c.o
.../src/xrt/compositor/main/comp_renderer.c:872:17: warning: unused variable 'layer_count' [-Wunused-variable]
const uint32_t layer_count = c->base.slot.layer_count;
^
1 warning generated.
-----------------------------------------------------------------------
Mark them as XRT_MAYBE_UNUSED to fix the build warnings.
