[gcc r17-3339] fortran: [PR95542] Fix ICE for deferred-length CHARACTER result via host association

https://gcc.gnu.org/g:47ec169c00cd1da6a9b0cecf871ccfb2a26fd63c

commit r17-3339-g47ec169c00cd1da6a9b0cecf871ccfb2a26fd63c
Author: Jerry DeLisle <[email protected]>
Date:   Sun Jul 12 15:25:18 2026 -0700

    fortran: [PR95542] Fix ICE for deferred-length CHARACTER result via host association
    
    gfc_get_symbol_decl has an assert meant to verify that a deferred-length
    string's length variable lives in the same scope as the symbol it
    belongs to.  This is wrong when sym->backend_decl is itself the enclosing
    function's FUNCTION_DECL.  The correct comparison is
    DECL_CONTEXT (length) == sym->backend_decl directly.
    
    This was hit when a deferred-length CHARACTER function's own result
    was assigned to or read from a CONTAINED subprocedure via host
    association.
    
            PR fortran/95542
    
    gcc/fortran/ChangeLog:
    
            * trans-decl.cc (gfc_get_symbol_decl): When checking that a
            deferred-length string's length variable shares the symbol's
            scope, special-case sym->backend_decl being a FUNCTION_DECL
            (an implicit function-result variable): compare against
            sym->backend_decl directly instead of its own DECL_CONTEXT.
    
    gcc/testsuite/ChangeLog:
    
            * gfortran.dg/pr95542.f90: New test.

Diff:
---
 gcc/fortran/trans-decl.cc             |  7 +++++--
 gcc/testsuite/gfortran.dg/pr95542.f90 | 21 +++++++++++++++++++++
 2 files changed, 26 insertions(+), 2 deletions(-)

diff --git a/gcc/fortran/trans-decl.cc b/gcc/fortran/trans-decl.cc
index e277f2b2ccc6..5678f69df9ca 100644
--- a/gcc/fortran/trans-decl.cc
+++ b/gcc/fortran/trans-decl.cc
@@ -1846,8 +1846,11 @@ gfc_get_symbol_decl (gfc_symbol * sym)
 		    gfc_add_decl_to_parent_function (length);
 		}
 
-	      gcc_assert (sym->backend_decl == current_function_decl
-			  ? DECL_CONTEXT (length) == current_function_decl
+	      /* When the symbol's own backend_decl is a FUNCTION_DECL, its
+		 DECL_CONTEXT is where that function itself is declared, not
+		 where its locals live.  */
+	      gcc_assert (TREE_CODE (sym->backend_decl) == FUNCTION_DECL
+			  ? DECL_CONTEXT (length) == sym->backend_decl
 			  : (DECL_CONTEXT (sym->backend_decl)
 			     == DECL_CONTEXT (length)));
 
diff --git a/gcc/testsuite/gfortran.dg/pr95542.f90 b/gcc/testsuite/gfortran.dg/pr95542.f90
new file mode 100644
index 000000000000..7bb541e7cba1
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr95542.f90
@@ -0,0 +1,21 @@
+! { dg-do run }
+! PR95542 - ICE in gfc_get_symbol_decl, at fortran/trans-decl.cc:1851
+!
+function f()
+  character(:), allocatable :: f
+  f = 'xyz'
+  call s
+contains
+  subroutine s
+    if (f /= 'xyz') stop 1
+  end subroutine s
+end function f
+
+program pr95542
+  interface
+    function f()
+      character(:), allocatable :: f
+    end function f
+  end interface
+  if (f() /= 'xyz') stop 2
+end program pr95542