Back in the 1990s, Borland Turbo C permitted this -- it even worked in some DOS memory models, because it depended on the 8088 or 80286 segment registers not be

Back in the 1990s, Borland Turbo C permitted this -- it even worked in some DOS memory models, because it depended on the 8088 or 80286 segment registers not being reused. I had to teach a cohort of developers who were migrating from Turbo C to a C89-compliant compiler. In C89 this was "undefined behavior".