macOS: Fix macOS 27 os_log compile errors, improve TRACE_VSYNC (#191238)
Suppress `-Wignored-attributes` triggered when compiling macOS-specific
logging and vsync tracing code.
In the macOS 27 SDK that's part of Xcode 27, Apple appears to have added
an `OS_LOG_UNINITIALIZED` macro inside their logging and signposting
headers (`os/log.h`, `os/signpost.h`, `os/trace_base.h`). This macro
expands to include: `__attribute__((stack_protector_ignore))`.
Because of this, we skip stack protection checks on local formatting
buffers generated by logging macros such as `os_log_with_type` and
`os_signpost_event_emit`. However, in Flutter, we compile the engine
with `-fstack-protector-all`, which causes the build to error out
complaining the `stack_protector_ignore` attribute is being ignored:
error: 'stack_protector_ignore' attribute ignored due to
'-fstack-protector-all' option [-Werror,-Wignored-attributes]
This wraps these usages in ignore pragmas to avoid disabling it across
the board, which is the same as the approach that was taken in:
*
https://github.com/dart-lang/sdk/commit/6bea1b7321870ddcccdf5274563b64977a115e5b
*
https://github.com/google/angle/commit/918b93f4c0f145b82871a6c515dce8ed90e7d6e0
This also creates the vsync log once and caches it statically as Apple
recommends. `os_log` is already multi-tenant safe.
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diff --git a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.mm b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.mm
index d5133cb..247fa20 100644
--- a/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.mm
+++ b/engine/src/flutter/shell/platform/darwin/macos/framework/Source/FlutterVSyncWaiter.mm
@@ -20,10 +20,12 @@
// Trace vsync events using os_signpost so that they can be seen in Instruments "Points of
// Interest".
-#define TRACE_VSYNC(event_type, baton) \
- do { \
- os_log_t log = os_log_create("FlutterVSync", "PointsOfInterest"); \
- os_signpost_event_emit(log, OS_SIGNPOST_ID_EXCLUSIVE, event_type, "baton %lx", baton); \
+#define TRACE_VSYNC(event_type, baton) \
+ do { \
+ static os_log_t log = os_log_create("FlutterVSync", "PointsOfInterest"); \
+ _Pragma("GCC diagnostic push") _Pragma("GCC diagnostic ignored \"-Wignored-attributes\"") \
+ os_signpost_event_emit(log, OS_SIGNPOST_ID_EXCLUSIVE, event_type, "baton %lx", baton); \
+ _Pragma("GCC diagnostic pop") \
} while (0)
#else
#define TRACE_VSYNC(event_type, baton) \
