[gcc r14-4147] fortran: fix checking of CHARACTER lengths in array constructors [PR70231]

[gcc r14-4147] fortran: fix checking of CHARACTER lengths in array constructors [PR70231]

[Harald Anlauf]

https://gcc.gnu.org/g:15acabb80f91b12836bcf4ffcb92ea10fe4e8272

commit r14-4147-g15acabb80f91b12836bcf4ffcb92ea10fe4e8272
Author: Harald Anlauf <anlauf@gmx.de>
Date:   Mon Sep 18 22:11:40 2023 +0200

    fortran: fix checking of CHARACTER lengths in array constructors [PR70231]
    
    gcc/fortran/ChangeLog:
    
            PR fortran/70231
            * trans-array.cc (trans_array_constructor): In absence of a typespec,
            use string length determined by get_array_ctor_strlen() to reasonably
            initialize auxiliary variable for bounds-checking.
    
    gcc/testsuite/ChangeLog:
    
            PR fortran/70231
            * gfortran.dg/bounds_check_fail_7.f90: New test.

Diff:
---
 gcc/fortran/trans-array.cc                        | 17 +++++++++++++++++
 gcc/testsuite/gfortran.dg/bounds_check_fail_7.f90 | 20 ++++++++++++++++++++
 2 files changed, 37 insertions(+)

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index 1640587cd71..e0fc8ebc46b 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -2852,6 +2852,23 @@ trans_array_constructor (gfc_ss * ss, locus * where)
 	  const_string = get_array_ctor_strlen (&outer_loop->pre, c,
 						&ss_info->string_length);
 	  force_new_cl = true;
+
+	  /* Initialize "len" with string length for bounds checking.  */
+	  if ((gfc_option.rtcheck & GFC_RTCHECK_BOUNDS)
+	      && !typespec_chararray_ctor
+	      && ss_info->string_length)
+	    {
+	      gfc_se length_se;
+
+	      gfc_init_se (&length_se, NULL);
+	      gfc_add_modify (&length_se.pre, first_len_val,
+			      fold_convert (TREE_TYPE (first_len_val),
+					    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);
+	    }
 	}
 
       /* Complex character array constructors should have been taken care of
diff --git a/gcc/testsuite/gfortran.dg/bounds_check_fail_7.f90 b/gcc/testsuite/gfortran.dg/bounds_check_fail_7.f90
new file mode 100644
index 00000000000..6a8dafc27a8
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/bounds_check_fail_7.f90
@@ -0,0 +1,20 @@
+! { dg-do run }
+! { dg-additional-options "-fcheck=bounds -g" }
+! { dg-output "At line 18 .*" }
+! { dg-shouldfail "Different CHARACTER lengths (32/0) in array constructor" }
+!
+! PR fortran/70231 - CHARACTER lengths in array constructors
+
+program p
+  implicit none
+  integer, parameter  :: char_len = 32
+  integer             :: l = 0
+  character(char_len) :: ch = "a"
+  character(char_len), allocatable :: ch_array(:), res1(:), res2(:)
+
+  allocate(ch_array(0))
+  res1 = [ ch_array, ch ]               ! was false positive
+  print *, res1
+  res2 = [[ch_array, ch(1:l)], ch(1:l)] ! was false negative on x86
+  print *, res2
+end