added COW_ERR_POISON

include/cow.h

@@ -18,6 +18,8 @@ enum cow_err_kind {
 	COW_ERR_SIZE,
 	/// `mmap()` failed.
 	COW_ERR_MAP,
+	/// Trying to use a poisoned cow
+	COW_ERR_POISONED,
 
 	_COW_ERR_SIZE,
 };

src/cow.c

@@ -122,7 +122,9 @@ void cow_free(cow_t* restrict cow)
 cow_t* cow_clone(const cow_t* cow)
 {
 	if(UNLIKELY(cow->poisoned)) {
+		_cow_set_err(COW_ERR_POISONED);
 		TRACE("WARNING: attempted to clone poisoned object at %p", (const void*)cow);
+	
 		return NULL;
 	}
 	cow_t clone;

src/error.cpp

@@ -21,6 +21,7 @@ namespace _cow_error {
 		setmsg(ret, COW_ERR_FDCREATE, "failed to create shmfd (memfd_create())");
 		setmsg(ret, COW_ERR_SIZE, "failed to set shmfd size (ftruncate())");
 		setmsg(ret, COW_ERR_MAP, "failed to map shmfd (mmap())");
+		setmsg(ret, COW_ERR_POISONED, "trying to use a poisoned cow");
 
 		return ret;
 	}