Fortran GCC interface compiler bug?

Why does GCC not warn me when I forget to specify the return type of a interface function? For me this behavior seams unexpected. What do you say to this?

This is the test-program (uncoment Line 6 and it works as it should):

program returntest
 implicit none
     interface
     function givehalf(Y)
       double precision :: Y
       !double precision :: givehalf !<-- Uncomment this line
     end function givehalf
     end interface
     double precision :: temp
 
 temp=givehalf(5.151515d0)
 print*, 'result=   ',temp
 
 end program returntest
 
 function givehalf(Y)
     implicit none
     double precision :: Y
     double precision :: givehalf
 
     print*, 'Y=        ',Y
     givehalf=Y/2.0d0
     print*, 'return Y/2',givehalf
 
     return
 end function givehalf
 

The result is this:

user@bapf028dl:/media/disk> gfortran44 -Wall return-test.f90
 user@bapf028dl:/media/disk> ./a.out
   Y=           5.1515149999999998     
   return Y/2   2.5757574999999999     
   result=     -1.0579199790954590     
 user@bapf028dl:/media/disk> ifort return-test.f90
 user@bapf028dl:/media/disk> ./a.out 
   Y=           5.15151500000000     
   return Y/2   2.57575750000000     
   result=      2.57575750350952 
 

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