Why does the arrow (->) operator in C exist?

And BTW, that global namespace for struct members is why old Unix style (still used today) prefixes all the member names. All the struct tm members start with tm_, and so forth.

This doesn’t really answer the question.

In order to dereference a pointer, the * operator needs to know the type of its operand. So C of that era had enough type information to know whether a variable was a pointer or not, and what type it pointed to.

So (in theory) it also had enough type information to know whether . should offset (if the left operand is a struct type) or indirect (otherwise). But in practice it didn’t pay attention to types in that manner, because of the way it gradually evolved from BCPL via B and NB.

This weirdness is also (weirdly) related to C’s weird treatment of arrays that decay to pointers. In BCPL, when you declare v[10] you get 10 slots for the array elements but also a -1th slot containing pointer to the start of the array (ie, v == &v + 1). So v!5 always treats v as a pointer to an array, and offsets the contents of the variable v (ie, its rvalue not its lvalue) by 5 words before fetching a value. In C there’s magic that avoids creating an explicit slot for the address of the array by magically making v evaluate to &v (ie, its rvalue is its lvalue) so that v[5] doesn’t waste a word for the indirection.

C could have done a similar thing for structs, so that s magically evaluates to &s such that s->m works when s is not a pointer. Or rather it would have used . for the indirection operator instead of -> because the decay-to-pointer would have made the non-dereferencing . redundant.

So the mystery is why C treats arrays and structs differently.

In 2026 this would be a bonkers language design, but I think the individual steps make sense in context. The original behavior of -> must have made the compiler implementation simpler or something? TIL, thanks for sharing!

Also, choice quote:

Needless to say, things like this could easily result in memory overrun, but the language did not concern itself with such matters.