core: Add xmalloc() implementation

Signed-off-by: Chloe M. <chloe@mirocom.org>

core/xmalloc.c

@@ -0,0 +1,24 @@
+/*
+ * Copyright (c) 2026, Chloe M.
+ * Provided under the BSD-3 clause
+ */
+
+#include <stdio.h>
+#include <stdlib.h>
+#include <stddef.h>
+#include <assert.h>
+#include "blobchain/memlib.h"
+
+void *
+xmalloc(size_t sz)
+{
+    void *p;
+
+    assert(sz != 0 && "xmalloc size cannot be zero!");
+    if ((p = malloc(sz)) == NULL) {
+        printf("fatal: out of memory\n");
+        exit(1);
+    }
+
+    return p;
+}