game-activity: tolerate the NULL pre-IME GameTextInput buffer - #252
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mudbungie wants to merge 1 commit into
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game-activity: tolerate the NULL pre-IME GameTextInput buffer#252mudbungie wants to merge 1 commit into
mudbungie wants to merge 1 commit into
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GameTextInput's initial state, delivered before the IME has attached, carries a NULL text pointer with length 0. The conversion callback fed it straight to slice::from_raw_parts, which requires a non-null pointer even for an empty slice: undefined behavior in release builds, and under debug_assertions the standard library's precondition check aborts the process (a non-unwinding panic inside an extern "C" callback) on the first frame of every debug build using the game-activity backend. Treat the NULL buffer as the empty text it represents.
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The defect
GameTextInputdelivers its initial state — before the IME has attached —with a NULL
text_UTF8pointer andtext_length == 0.map_input_state_to_text_event_callbackfeeds that pointer straight tostd::slice::from_raw_parts, whose contract requires a non-null pointereven for a zero-length slice. That is undefined behavior in release builds,
and under
debug_assertionsthe standard library's precondition checkfires: a non-unwinding panic inside an
extern "C"callback, i.e. animmediate abort.
Observed
Every debug build of a
game-activity-backend app closes on its firstframe (observed with android-activity 0.6.1 + androidx games-activity
4.4.0, egui/winit app, current-generation Pixel, SDK 35). The tombstone
points at the stdlib's
from_raw_partsprecondition inside the callback.Release builds compile the check out and happen to survive the len-0 read,
which makes the failure look like a debug-only mystery rather than what it
is — UB reached on every launch.
The fix
Treat the NULL buffer as the empty text it represents before constructing
the slice. One guard, no behavior change for any non-null buffer.