software_revoker: revoker_tick return 0

Quiet the compiler's warning of void cross-compartment calls

sdk/core/allocator/revoker.h

diff --git a/sdk/core/allocator/revoker.h b/sdk/core/allocator/revoker.h
index e484b4f..891445d 100644
--- a/sdk/core/allocator/revoker.h
+++ b/sdk/core/allocator/revoker.h
@@ -389,7 +389,7 @@
 			// time that it's queried.
 			if ((current & 1) == 1)
 			{
-				revoker_tick();
+				(void)revoker_tick();
 				current = *epoch;
 			}
 			// We want to know if current is greater than epoch, but current
@@ -415,7 +415,7 @@
 		/// Start revocation running.
 		void system_bg_revoker_kick()
 		{
-			revoker_tick();
+			(void)revoker_tick();
 		}
 	};
 

sdk/core/allocator/software_revoker.h

diff --git a/sdk/core/allocator/software_revoker.h b/sdk/core/allocator/software_revoker.h
index 561e021..11066ca 100644
--- a/sdk/core/allocator/software_revoker.h
+++ b/sdk/core/allocator/software_revoker.h
@@ -6,10 +6,14 @@
 
 /**
  * Prod the software revoker to do some work.  This does not do a complete
- * revocation pass, it will scan a region of memory and then return.
+ * revocation pass; it will scan a region of memory and then return.
+ *
+ * Returns 0 on success, a compartment invocation failure indication
+ * (-ENOTENOUGHSTACK, -ENOTENOUGHTRUSTEDSTACK) if it cannot be invoked, or
+ * possibly -ECOMPARTMENTFAIL if the software revoker compartment is damaged.
  */
 [[cheri::interrupt_state(disabled)]] __cheri_compartment(
-  "software_revoker") void revoker_tick();
+  "software_revoker") int revoker_tick();
 
 /**
  * Returns a read-only capability to the current revocation epoch.  If the low

sdk/core/software_revoker/revoker.cc

diff --git a/sdk/core/software_revoker/revoker.cc b/sdk/core/software_revoker/revoker.cc
index 445c778..3db6041 100644
--- a/sdk/core/software_revoker/revoker.cc
+++ b/sdk/core/software_revoker/revoker.cc
@@ -159,7 +159,7 @@
 
 } // namespace
 
-void revoker_tick()
+int revoker_tick()
 {
 	// If we've been asked to run, make sure that we're running.
 	if (state == State::NotRunning)
@@ -167,7 +167,9 @@
 		advance();
 	}
 	// Do some work.
-	return scan_range();
+	scan_range();
+
+	return 0;
 }
 
 const uint32_t *revoker_epoch_get()