[gcc r17-1158] Fortran: Fix submodule access to private symbols in parent module [PR88632, 104630]

[Paul Thomas]

https://gcc.gnu.org/g:9fc5a7a25e9e29f58359c6363c9b10a99c6f99f0

commit r17-1158-g9fc5a7a25e9e29f58359c6363c9b10a99c6f99f0
Author: Paul Thomas <pault@gcc.gnu.org>
Date:   Mon Jun 1 12:40:53 2026 +0100

    Fortran: Fix submodule access to private symbols in parent module [PR88632,104630]
    
    PRs 88632 and 104630 both suffered link a problem, where a private procedure
    in a parent module was not visible in a descendent submodule if they were
    compiled separately.
    
    The fix is to not filter out private symbols when writing the .smod file.
    Submodules are descendants of their ancestor module and access private symbols
    in the module's contains section via host association (F2018 14.2.2).
    
    The testcase here is that of PR104630. However, it is functionally identical
    to that of PR88632.
    
    2026-06-02  Paul Thomas  <pault@gcc.gnu.org>
    
    gcc/fortran
            PR fortran/88632
            PR fortran/104630
            * module.cc (write_symtree): Do not filter out private symbols
            when writing a submodule interface file (.smod).  Submodules are
            descendants of their ancestor module and access private symbols
            in the module's contains section via host association per
            Fortran 2018 section 14.2.2.
    
    gcc/testsuite/
            PR fortran/88632
            PR fortran/104630
            * gfortran.dg/submodule_35.f90: New test.
            * gfortran.dg/submodule_35_aux.f90: Submodule and program for
            for the new test.
    
            Assisted by: Claude Sonnet 4.6

Diff:
---
 gcc/fortran/module.cc                          |  3 ++-
 gcc/testsuite/gfortran.dg/submodule_35.f90     | 32 ++++++++++++++++++++++++++
 gcc/testsuite/gfortran.dg/submodule_35_aux.f90 | 19 +++++++++++++++
 3 files changed, 53 insertions(+), 1 deletion(-)

diff --git a/gcc/fortran/module.cc b/gcc/fortran/module.cc
index ac071cd276bc..fa560f7ef467 100644
--- a/gcc/fortran/module.cc
+++ b/gcc/fortran/module.cc
@@ -6643,7 +6643,8 @@ write_symtree (gfc_symtree *st)
 	&& sym->ns->proc_name->attr.if_source == IFSRC_IFBODY)
     return;
 
-  if (!gfc_check_symbol_access (sym)
+  if ((!gfc_check_symbol_access (sym)
+       && (!sym->attr.public_used || submodule_name == NULL))
       || (sym->attr.flavor == FL_PROCEDURE && sym->attr.generic
 	  && !sym->attr.subroutine && !sym->attr.function))
     return;
diff --git a/gcc/testsuite/gfortran.dg/submodule_35.f90 b/gcc/testsuite/gfortran.dg/submodule_35.f90
new file mode 100644
index 000000000000..8bced2e2d7fb
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/submodule_35.f90
@@ -0,0 +1,32 @@
+! { dg-do run )
+!
+! Test the fix for prs 88632 and 104630, in which the private procedure
+! 'my_number' was not visible in the submodule 'decendent'.
+!
+! Contributed by Joerg Stiller <joerg.stiller@tu-dresden.de>
+!             and Neil Carlson  <neil.n.carlson@gmail.com>
+!
+module parent
+  private
+  public :: my_type
+  
+  type my_type
+    integer :: i = 1
+  contains
+    procedure :: my_method
+  end type my_type
+  
+  interface
+    module subroutine my_method(this)
+      class(my_type), intent(inout) :: this
+    end subroutine my_method
+  end interface
+  
+contains
+  
+  ! common helper function to be used in different submodules
+  integer function my_number()
+    my_number = 42
+  end function my_number
+
+end module parent
diff --git a/gcc/testsuite/gfortran.dg/submodule_35_aux.f90 b/gcc/testsuite/gfortran.dg/submodule_35_aux.f90
new file mode 100644
index 000000000000..0330b8f06d73
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/submodule_35_aux.f90
@@ -0,0 +1,19 @@
+! { dg-do run }
+! { dg-compile-aux-modules "submodule_35.f90" }
+! { dg-additional-sources submodule_35.f90 }
+!
+submodule(parent) decendent
+contains
+  module subroutine my_method(this)
+    class(my_type), intent(inout) :: this
+    this%i = my_number()
+  end subroutine my_method
+end submodule decendent
+
+program main
+  use parent
+  type(my_type) :: my
+  call my % my_method()
+  if (my%i /= 42) stop 1
+end program main
+! { dg-final { cleanup-modules "parent" } }