fix(core/remio): use of zero-sized array

The specific error is triggered in the macro expansion for
OBJPOOL_ALLOC when the value CONFIG_REMIO_DEV_NUM assumes the
value of 0.
To solve this problem, we allocate only one slot if the user
does not configure any Remote I/O device.

Note: While we could use the #if macro to define the object pool
only when a Remote I/O is configured, this approach would clutter
the code with constant checks for device configuration whenever
accessing certain variables.

Signed-off-by: João Peixoto <[email protected]>

src/core/remio.c

@@ -138,7 +138,8 @@ static void remio_cpu_handler(uint32_t event, uint64_t data);
 CPU_MSG_HANDLER(remio_cpu_handler, REMIO_CPUMSG_ID)
 
 /** Object pool to allocate Remote I/O devices */
-OBJPOOL_ALLOC(remio_device_pool, struct remio_device, CONFIG_REMIO_DEV_NUM);
+OBJPOOL_ALLOC(remio_device_pool, struct remio_device,
+    CONFIG_REMIO_DEV_NUM ? CONFIG_REMIO_DEV_NUM : 1);
 
 /** Object pool to allocate pending Remote I/O requests events */
 OBJPOOL_ALLOC(remio_request_event_pool, struct remio_request_event, REMIO_VCPU_NUM);

src/core/vm.c

@@ -11,7 +11,7 @@
 #include <shmem.h>
 #include <objpool.h>
 
-OBJPOOL_ALLOC(emul_cache, struct emul_mem, CONFIG_REMIO_DEV_NUM);
+OBJPOOL_ALLOC(emul_cache, struct emul_mem, CONFIG_REMIO_DEV_NUM ? CONFIG_REMIO_DEV_NUM : 1);
 
 static void vm_master_init(struct vm* vm, const struct vm_config* vm_config, vmid_t vm_id)
 {