&gt; Sometimes C compilers can&#x27;t even agree on what counts as &quot;correct&quot;!<p>This comes primarily from the fact the C standard itself is hard to interpret right. Standard ML has less issues in this department: since the Definition is clearer and less ambiguous, implementations disagree less on what counts as correct code and what its meaning is. So having only one major language implementation isn&#x27;t the only way to prevent compatibility issues.