[gcc r16-1576] fortran: Statically initialize length of SAVEd character arrays

[Mikael Morin via Gcc-cvs]

https://gcc.gnu.org/g:95cc39dd47419d0544a0e1b32292ba250155a112

commit r16-1576-g95cc39dd47419d0544a0e1b32292ba250155a112
Author: Mikael Morin <mik...@gcc.gnu.org>
Date:   Wed Jun 18 22:11:43 2025 +0200

    fortran: Statically initialize length of SAVEd character arrays
    
            PR fortran/120713
    
    gcc/fortran/ChangeLog:
    
            * trans-array.cc (gfc_trans_deferred_array): Statically
            initialize deferred length variable for SAVEd character arrays.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/save_alloc_character_1.f90: New test.

Diff:
---
 gcc/fortran/trans-array.cc                         | 12 +++++++++--
 .../gfortran.dg/save_alloc_character_1.f90         | 23 ++++++++++++++++++++++
 2 files changed, 33 insertions(+), 2 deletions(-)

diff --git a/gcc/fortran/trans-array.cc b/gcc/fortran/trans-array.cc
index 960613167f72..3d274439895d 100644
--- a/gcc/fortran/trans-array.cc
+++ b/gcc/fortran/trans-array.cc
@@ -12067,8 +12067,16 @@ gfc_trans_deferred_array (gfc_symbol * sym, 
gfc_wrapped_block * block)
       && !INTEGER_CST_P (sym->ts.u.cl->backend_decl))
     {
       if (sym->ts.deferred && !sym->ts.u.cl->length && !sym->attr.dummy)
-       gfc_add_modify (&init, sym->ts.u.cl->backend_decl,
-                       build_zero_cst (TREE_TYPE 
(sym->ts.u.cl->backend_decl)));
+       {
+         tree len_expr = sym->ts.u.cl->backend_decl;
+         tree init_val = build_zero_cst (TREE_TYPE (len_expr));
+         if (VAR_P (len_expr)
+             && sym->attr.save
+             && !DECL_INITIAL (len_expr))
+           DECL_INITIAL (len_expr) = init_val;
+         else
+           gfc_add_modify (&init, len_expr, init_val);
+       }
       gfc_conv_string_length (sym->ts.u.cl, NULL, &init);
       gfc_trans_vla_type_sizes (sym, &init);
 
diff --git a/gcc/testsuite/gfortran.dg/save_alloc_character_1.f90 
b/gcc/testsuite/gfortran.dg/save_alloc_character_1.f90
new file mode 100644
index 000000000000..e26919f83bea
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/save_alloc_character_1.f90
@@ -0,0 +1,23 @@
+! { dg-do run }
+!
+! PR fortran/120713
+! Check that the length variable of SAVEd allocatable character arrays are
+! not initialized at function entry.
+
+program p
+  implicit none
+  call s(1)
+  call s(2)
+contains
+  subroutine s(i)
+    integer, intent(in) :: i
+    character(len=:), allocatable, save :: a(:)
+    integer :: j
+    if (i == 1) then
+      allocate(a, source= [ ('x' // achar(ichar('0') + j), j=1,7) ])
+    else
+      if (len(a) /= 2) error stop 1
+      if (any(a /= ['x1','x2','x3','x4','x5','x6','x7'])) error stop 2
+    end if
+  end subroutine s
+end program p