gcc/testsuite/gfortran.dg/char_length_20.f90

! { dg-do run }
! { dg-options "-fcheck=bounds" }
program rabbithole
   implicit none
   character(len=:), allocatable :: text_block(:)
   integer i, ii
   character(len=10) :: cten='abcdefghij'
   character(len=20) :: ctwenty='abcdefghijabcdefghij'
   ii = -6
   text_block=[ character(len=ii) :: cten, ctwenty ]
   if (any(len_trim(text_block) /= 0)) STOP 1
end program rabbithole
! { dg-output "At line 10 of file .*char_length_20.f90.*Fortran runtime warning: Negative character length treated as LEN = 0" }