Files opened without an explicit ACTION= specifier (The GNU Fortran Compiler)

### 4.7 Files opened without an explicit `ACTION=` specifier ¶

The Fortran standard says that if an `OPEN` statement is executed without an explicit `ACTION=` specifier, the default value is processor dependent. GNU Fortran behaves as follows:

1. Attempt to open the file with `ACTION='READWRITE'`
2. If that fails, try to open with `ACTION='READ'`
3. If that fails, try to open with `ACTION='WRITE'`
4. If that fails, generate an error