C, Fortran, and single-character strings

To pass an integer that is to be interpreted as an enumeration value, you also pass just a pointer. In Fortran, enumeration values are conventionally assigned character codes. They're not strings, they're just convenient literal notation for a symbol. Passing a pointer to a character is just the language idiom for an enumerated-value argument.

But passing a pointer to a character is not wrong or fragile code. Changing a library to fail without an extra length argument, after conventional usage is well-established, would be. If, in fact, maintainers of Fortran libraries are doing that, shame on THEM. I see no reason for C users of Fortran libraries to be embarrassed. Their code is not wrong or fragile, absent specific documentation of the original library to the contrary. Changing the compiler to forbid this usage would be wrong.

If you look at the libraries in question, you will probably find places where an argument interpreted as an enumerator is followed by another actual argument, where inserting another, length, argument would produce the wrong result, or a crash.

This attitude is accepting reality and not naming something inconvenient fake facts. If something works than it works - fact. The goal isn't simply to get something to work, it is to get something to work safe and reliable. This distinction between simply working (maybe only backed by luck) and good engineering is the topic of the woodpecker comment.