If you could change meaning of int to be 64-bit type, then your code ABI (<a href="https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Application_binary_interface" rel="nofollow">https:&#x2F;&#x2F;en.wikipedia.org&#x2F;wiki&#x2F;Application_binary_interface</a>) would be essentially incompatible, and you wouldn&#x27;t be able to use code (such as standard library, or other headers provided by operating system libraries) that was compiled on a compiler where int was 32-bit, as for instance wrong structure fields would be read.<p>If you would try to &quot;solve&quot; that by assuming headers use 32-bit int definition, then you would break calling your own code, as you would use 32-bit int definition provided in headers, while your code was called with 64-bit int convention.<p>It&#x27;s probably just easier to define your own int meaning type, say, a shorter alias of int_fast32_t.