Please excuse the messy formatting in my initial mail. Resending with proper formatting.
This patch checks for negative character length in the array constructor, and treats it as LEN=0. A warning message is also printed if bounds checking is enabled. Bootstrapped and regression tested the patch on x86_64-linux-gnu and aarch64-linux-gnu. Index: ChangeLog =================================================================== --- ChangeLog (revision 242906) +++ ChangeLog (working copy) @@ -1,3 +1,9 @@ +2016-11-30 Elizebeth Punnoose <elizebeth.punno...@hpe.com> + + PR fortran/77505 + * trans-array.c (trans_array_constructor): Treat negative character + length as LEN=0. + 2016-11-27 Paul Thomas <pa...@gcc.gnu.org> PR fortran/78474 Index: trans-array.c =================================================================== --- trans-array.c (revision 242906) +++ trans-array.c (working copy) @@ -2226,6 +2226,8 @@ trans_array_constructor (gfc_ss * ss, lo gfc_ss_info *ss_info; gfc_expr *expr; gfc_ss *s; + tree neg_len; + char *msg; /* Save the old values for nested checking. */ old_first_len = first_len; @@ -2271,6 +2273,28 @@ trans_array_constructor (gfc_ss * ss, lo gfc_conv_expr_type (&length_se, expr->ts.u.cl->length, gfc_charlen_type_node); ss_info->string_length = length_se.expr; + + /* Check if the character length is negative, + if so consider it as LEN=0. */ + neg_len = fold_build2_loc (input_location, LT_EXPR, + boolean_type_node, ss_info->string_length, + build_int_cst (gfc_charlen_type_node, 0)); + /* Print a warning if bounds checking is enabled. */ + if (gfc_option.rtcheck & GFC_RTCHECK_BOUNDS) + { + msg = xasprintf ("Negative character length will be treated" + " as LEN=0"); + gfc_trans_runtime_check (false, true, neg_len, &length_se.pre, + where, msg); + free (msg); + } + ss_info->string_length = fold_build3_loc (input_location, COND_EXPR, + gfc_charlen_type_node, neg_len, + build_int_cst (gfc_charlen_type_node, 0), + ss_info->string_length); + ss_info->string_length = gfc_evaluate_now (ss_info->string_length, + &length_se.pre); + gfc_add_block_to_block (&outer_loop->pre, &length_se.pre); gfc_add_block_to_block (&outer_loop->post, &length_se.post); } Index: ChangeLog =================================================================== --- ChangeLog (revision 242906) +++ ChangeLog (working copy) @@ -1,3 +1,9 @@ +2016-11-30 Elizebeth Punnoose <elizebeth.punno...@hpe.com> + + PR fortran/77505 + * gfortran.dg/pr77505_1.f90: New test. + * gfortran.dg/pr77505_2.f90: New test. + 2016-11-27 Paul Thomas <pa...@gcc.gnu.org> PR fortran/78474 Index: pr77505_1.f90 =================================================================== --- pr77505_1.f90 (nonexistent) +++ pr77505_1.f90 (working copy) @@ -0,0 +1,13 @@ +! { dg-do run } +program rabbithole +implicit none +character(len=:),allocatable :: text_block(:) integer +:: i integer :: ii +character(len=10) :: cten='abcdefghij' +character(len=20) :: ctwenty='abcdefghijabcdefghij' +ii=-6 +text_block=[ character(len=ii) :: cten, ctwenty ] write(*,*)'WRITE IT' +write(*,'(a)')(trim(text_block(i)),i=1,size(text_block)) +end program rabbithole Index: pr77505_2.f90 =================================================================== --- pr77505_2.f90 (nonexistent) +++ pr77505_2.f90 (working copy) @@ -0,0 +1,14 @@ +! { dg-options "-fcheck=bounds" } +! { dg-do run } +program rabbithole +implicit none +character(len=:),allocatable :: text_block(:) +integer :: i +integer :: ii +character(len=10) :: cten='abcdefghij' +character(len=20) :: ctwenty='abcdefghijabcdefghij' +ii=-6 +text_block=[ character(len=ii) :: cten, ctwenty ] +write(*,*)'WRITE IT' +write(*,'(a)')(trim(text_block(i)),i=1,size(text_block)) +end program rabbithole Thanks, Elizebeth