selftests/bpf: Fix "expression result unused" warnings with icecc

tools/lib/bpf/bpf_helpers.h

@@ -69,6 +69,10 @@
  */
 #define __hidden __attribute__((visibility("hidden")))
 
+#ifndef __must_check
+#define __must_check __attribute__((__warn_unused_result__))
+#endif
+
 /* When utilizing vmlinux.h with BPF CO-RE, user BPF programs can't include
  * any system-level headers (such as stddef.h, linux/version.h, etc), and
  * commonly-used macros like NULL and KERNEL_VERSION aren't available through

tools/testing/selftests/bpf/bpf_experimental.h

@@ -20,7 +20,7 @@
  *	A pointer to an object of the type corresponding to the passed in
  *	'local_type_id', or NULL on failure.
  */
-extern void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
+extern __must_check void *bpf_obj_new_impl(__u64 local_type_id, void *meta) __ksym;
 
 /* Convenience macro to wrap over bpf_obj_new_impl */
 #define bpf_obj_new(type) ((type *)bpf_obj_new_impl(bpf_core_type_id_local(type), NULL))

tools/testing/selftests/bpf/progs/bpf_arena_spin_lock.h

@@ -302,7 +302,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
 	 * barriers.
 	 */
 	if (val & _Q_LOCKED_MASK)
-		smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
+		(void)smp_cond_load_acquire_label(&lock->locked, !VAL, release_err);
 
 	/*
 	 * take ownership and clear the pending bit.
@@ -380,7 +380,7 @@ int arena_spin_lock_slowpath(arena_spinlock_t __arena __arg_arena *lock, u32 val
 		/* Link @node into the waitqueue. */
 		WRITE_ONCE(prev->next, node);
 
-		arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
+		(void)arch_mcs_spin_lock_contended_label(&node->locked, release_node_err);
 
 		/*
 		 * While waiting for the MCS lock, the next pointer may have

tools/testing/selftests/bpf/progs/linked_list_fail.c

@@ -212,22 +212,22 @@ int map_compat_raw_tp_w(void *ctx)
 SEC("?tc")
 int obj_type_id_oor(void *ctx)
 {
-	bpf_obj_new_impl(~0UL, NULL);
+	(void)bpf_obj_new_impl(~0UL, NULL);
 	return 0;
 }
 
 SEC("?tc")
 int obj_new_no_composite(void *ctx)
 {
-	bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
+	(void)bpf_obj_new_impl(bpf_core_type_id_local(int), (void *)42);
 	return 0;
 }
 
 SEC("?tc")
 int obj_new_no_struct(void *ctx)
 {
 
-	bpf_obj_new(union { int data; unsigned udata; });
+	(void)bpf_obj_new(union { int data; unsigned udata; });
 	return 0;
 }
 
@@ -252,7 +252,7 @@ int new_null_ret(void *ctx)
 SEC("?tc")
 int obj_new_acq(void *ctx)
 {
-	bpf_obj_new(struct foo);
+	(void)bpf_obj_new(struct foo);
 	return 0;
 }