[Flang] Compilation error of interface and end interface statement with read (formatted) as defined-io-generic-spec

[ohno-fj]

Version of flang : 21.0.0(b2b3cb5f76f15d38e67f70124d275a5696bfdb83)/AArch64

interface and end interface statement with read (formatted) as defined-io-generic-spec fails the linker command.
When read (formatted) is removed from interface and end interface statement, the compilation is successful.

The following are the test program, Flang, Gfortran and ifx compilation/execution result.

sngg521n_21.f90:

PROGRAM MAIN
  TYPE T
     INTEGER::A
  END TYPE T
  INTERFACE READ(FORMATTED)
     SUBROUTINE SUB1 (DTV, UNIT, IOTYPE, V_LIST, IOSTAT, IOMSG)
       IMPORT T
       CLASS(T), INTENT(INOUT)         :: DTV
       INTEGER, INTENT(IN)             :: UNIT
       CHARACTER(LEN=*), INTENT(IN)    :: IOTYPE
       INTEGER, INTENT(IN)             :: V_LIST (:)
       INTEGER, INTENT(OUT)            :: IOSTAT
       CHARACTER(LEN=*), INTENT(INOUT) :: IOMSG
     END SUBROUTINE SUB1
  END INTERFACE READ(FORMATTED)
  print *,'pass'
END PROGRAM MAIN

$ flang sngg521n_21.f90
/opt/rh/gcc-toolset-12/root/usr/lib/gcc/aarch64-redhat-linux/12/../../../../bin/ld: /tmp/sngg521n_21-1789ed.o:(.data.rel.ro._QFEXsXt[_QFEXsXt]+0x8): undefined reference to `sub1_'
flang-20: error: linker command failed with exit code 1 (use -v to see invocation)
$

$ gfortran sngg521n_21.f90; ./a.out
 pass
$

$ ifx sngg521n_21.f90; ./a.out
 pass
$

[klausler]

You declared a defined I/O procedure for a type, but never defined it.