diff mbox series

[fortran] PR112407 - [13/14 Regression] Fix for PR37336 triggers an ICE in gfc_format_decoder while constructing a vtab

Message ID CAGkQGi+aQ+u-rkEsp=tX8vfW8wabDMotRvte+N7pqcTT5iM_Yg@mail.gmail.com
State New
Headers show
Series [fortran] PR112407 - [13/14 Regression] Fix for PR37336 triggers an ICE in gfc_format_decoder while constructing a vtab | expand

Commit Message

Paul Richard Thomas March 30, 2024, 9:06 a.m. UTC
Hi All,

This bug emerged in a large code and involves possible recursion with a
"hidden" module procedure; ie. where the symtree name starts with '@'. This
throws the format decoder. As the last message in the PR shows, I have
vacillated between silently passing on the possible recursion or adding an
alternative warning message. In the end, as a conservative choice I went
for emitting the message.

In the course of trying to develop a compact test case, I found that type
bound procedures were not being tested for recursion and that class
dummies, with intent out, were being incorrectly initialized with an empty
default initializer. Both of these have been fixed.

Unfortunately, the most compact reproducer that Tomas was able to come up
with required more than 100kbytes of module files. I tried from the bottom
up but failed. Both the tests check the fixes for the other bugs.

Regtests on x86_64 - OK for mainline and, in a couple of weeks, 13-branch?

Paul

Fortran: Fix wrong recursive errors and class initialization [PR112407]

2024-03-30  Paul Thomas  <pault@gcc.gnu.org>

gcc/fortran
PR fortran/112407
*resolve.cc (resolve_procedure_expression): Change the test for
for recursion in the case of hidden procedures from modules.
(resolve_typebound_static): Add warning for possible recursive
calls to typebound procedures.
* trans-expr.cc (gfc_trans_class_init_assign): Do not apply
default initializer to class dummy where component initializers
are all null.

gcc/testsuite/
PR fortran/112407
* gfortran.dg/pr112407a.f90: New test.
* gfortran.dg/pr112407b.f90: New test.

Comments

Harald Anlauf March 30, 2024, 2:52 p.m. UTC | #1
Hi Paul,

I had only a quick glance at your patch.  I guess you unintentionally
forgot to remove those parts that you already committed for PR110987,
along with the finalize-testcases.

I am still trying to find the precise paragraph in the standard
you refer to regarding INTENT(OUT) and default initialization.

While at it, I think I found a minor nit in testcase pr112407a.f90:
component x%i appears undefined the first time it is printed.
This can be verified by either adding an explicit

   x% i = -42

in the main after the allocate(x).  Alternatively, running the
code with Intel and using MALLOC_PERTURB_ shows a random arg1%i,
but is otherwise fine.  However, if by chance (random memory)

   x% i = +42

then the test would likely fail everywhere.

Cheers,
Harald


Am 30.03.24 um 10:06 schrieb Paul Richard Thomas:
> Hi All,
>
> This bug emerged in a large code and involves possible recursion with a
> "hidden" module procedure; ie. where the symtree name starts with '@'. This
> throws the format decoder. As the last message in the PR shows, I have
> vacillated between silently passing on the possible recursion or adding an
> alternative warning message. In the end, as a conservative choice I went
> for emitting the message.
>
> In the course of trying to develop a compact test case, I found that type
> bound procedures were not being tested for recursion and that class
> dummies, with intent out, were being incorrectly initialized with an empty
> default initializer. Both of these have been fixed.
>
> Unfortunately, the most compact reproducer that Tomas was able to come up
> with required more than 100kbytes of module files. I tried from the bottom
> up but failed. Both the tests check the fixes for the other bugs.
>
> Regtests on x86_64 - OK for mainline and, in a couple of weeks, 13-branch?
>
> Paul
>
> Fortran: Fix wrong recursive errors and class initialization [PR112407]
>
> 2024-03-30  Paul Thomas  <pault@gcc.gnu.org>
>
> gcc/fortran
> PR fortran/112407
> *resolve.cc (resolve_procedure_expression): Change the test for
> for recursion in the case of hidden procedures from modules.
> (resolve_typebound_static): Add warning for possible recursive
> calls to typebound procedures.
> * trans-expr.cc (gfc_trans_class_init_assign): Do not apply
> default initializer to class dummy where component initializers
> are all null.
>
> gcc/testsuite/
> PR fortran/112407
> * gfortran.dg/pr112407a.f90: New test.
> * gfortran.dg/pr112407b.f90: New test.
>
Paul Richard Thomas March 31, 2024, 12:08 p.m. UTC | #2
Hi Harald,

>
> I had only a quick glance at your patch.  I guess you unintentionally
> forgot to remove those parts that you already committed for PR110987,
> along with the finalize-testcases.
>

Guilty as charged. I guess I got out of the wrong side of the bed :-)

>
> I am still trying to find the precise paragraph in the standard
> you refer to regarding INTENT(OUT) and default initialization.
>

Page 114 of the draft F2023 standard:
"The INTENT (OUT) attribute for a nonpointer dummy argument specifies that
the dummy argument becomes undefined on invocation of the procedure, except
for any subcomponents that are default-initialized (7.5.4.6)."
With the fix, gfortran behaves in the same way as ifort and nagfor.

On rereading the patch, I think that s/"and use the passed value"/"and
leave undefined"/ or some such is in order.


> While at it, I think I found a minor nit in testcase pr112407a.f90:
> component x%i appears undefined the first time it is printed.
>

Fixed - thanks for pointing it out.

A correct patch is attached.

Thanks for looking at the previous, overloaded version.

Paul



>
> > 2024-03-30  Paul Thomas  <pault@gcc.gnu.org>
> >
> > gcc/fortran
> > PR fortran/112407
> > *resolve.cc (resolve_procedure_expression): Change the test for
> > for recursion in the case of hidden procedures from modules.
> > (resolve_typebound_static): Add warning for possible recursive
> > calls to typebound procedures.
> > * trans-expr.cc (gfc_trans_class_init_assign): Do not apply
> > default initializer to class dummy where component initializers
> > are all null.
> >
> > gcc/testsuite/
> > PR fortran/112407
> > * gfortran.dg/pr112407a.f90: New test.
> > * gfortran.dg/pr112407b.f90: New test.
> >
>
>
Harald Anlauf April 1, 2024, 8:04 p.m. UTC | #3
Hi Paul!

Am 31.03.24 um 14:08 schrieb Paul Richard Thomas:
> Hi Harald,
> 
>>
>> I had only a quick glance at your patch.  I guess you unintentionally
>> forgot to remove those parts that you already committed for PR110987,
>> along with the finalize-testcases.
>>
> 
> Guilty as charged. I guess I got out of the wrong side of the bed :-)
> 
>>
>> I am still trying to find the precise paragraph in the standard
>> you refer to regarding INTENT(OUT) and default initialization.
>>
> 
> Page 114 of the draft F2023 standard:
> "The INTENT (OUT) attribute for a nonpointer dummy argument specifies that
> the dummy argument becomes undefined on invocation of the procedure, except
> for any subcomponents that are default-initialized (7.5.4.6)."
> With the fix, gfortran behaves in the same way as ifort and nagfor.
> 
> On rereading the patch, I think that s/"and use the passed value"/"and
> leave undefined"/ or some such is in order.

Yes, something along this line is better.

I also did test with NAG and Intel, and was surprised (confused?) at how
the count of finalizer calls changes if component "i" gets a default
value or not.  Something one wouldn't do right after getting out of bed!

So the patch looks good to me - except for one philosophical question:

Fortran 2018 makes procedures recursive by default, but this is not
yet implemented as such, and NON_RECURSIVE is not yet implemented.

The new testcase pr112407b.f90 compiles with nagfor -f2018 without
any warnings, and gives an error with nagfor -f2008.  It appears
that it works in the testsuite after the patch and when adding
"-std=f2008" instead of using the default "-std=gnu".

Would you mind adding "-std=f2008" as dg-option to that testcase?
This would avoid one bogus regression when gfortran moves forward.

Thanks for the patch!

Harald

> 
>> While at it, I think I found a minor nit in testcase pr112407a.f90:
>> component x%i appears undefined the first time it is printed.
>>
> 
> Fixed - thanks for pointing it out.
> 
> A correct patch is attached.
> 
> Thanks for looking at the previous, overloaded version.
> 
> Paul
> 
> 
> 
>>
>>> 2024-03-30  Paul Thomas  <pault@gcc.gnu.org>
>>>
>>> gcc/fortran
>>> PR fortran/112407
>>> *resolve.cc (resolve_procedure_expression): Change the test for
>>> for recursion in the case of hidden procedures from modules.
>>> (resolve_typebound_static): Add warning for possible recursive
>>> calls to typebound procedures.
>>> * trans-expr.cc (gfc_trans_class_init_assign): Do not apply
>>> default initializer to class dummy where component initializers
>>> are all null.
>>>
>>> gcc/testsuite/
>>> PR fortran/112407
>>> * gfortran.dg/pr112407a.f90: New test.
>>> * gfortran.dg/pr112407b.f90: New test.
>>>
>>
>>
>
diff mbox series

Patch

diff --git a/gcc/fortran/resolve.cc b/gcc/fortran/resolve.cc
index 50d51b06c92..43315a6a550 100644
--- a/gcc/fortran/resolve.cc
+++ b/gcc/fortran/resolve.cc
@@ -1963,12 +1963,20 @@  resolve_procedure_expression (gfc_expr* expr)
       || (sym->attr.function && sym->result == sym))
     return true;
 
-  /* A non-RECURSIVE procedure that is used as procedure expression within its
+   /* A non-RECURSIVE procedure that is used as procedure expression within its
      own body is in danger of being called recursively.  */
   if (is_illegal_recursion (sym, gfc_current_ns))
-    gfc_warning (0, "Non-RECURSIVE procedure %qs at %L is possibly calling"
-		 " itself recursively.  Declare it RECURSIVE or use"
-		 " %<-frecursive%>", sym->name, &expr->where);
+    {
+      if (sym->attr.use_assoc && expr->symtree->name[0] == '@')
+	gfc_warning (0, "Non-RECURSIVE procedure %qs from module %qs is "
+		     " possibly calling itself recursively in procedure %qs. "
+		     " Declare it RECURSIVE or use %<-frecursive%>",
+		     sym->name, sym->module, gfc_current_ns->proc_name->name);
+      else
+	gfc_warning (0, "Non-RECURSIVE procedure %qs at %L is possibly calling"
+		     " itself recursively.  Declare it RECURSIVE or use"
+		     " %<-frecursive%>", sym->name, &expr->where);
+    }
 
   return true;
 }
@@ -6820,6 +6828,13 @@  resolve_typebound_static (gfc_expr* e, gfc_symtree** target,
       if (st)
 	*target = st;
     }
+
+  if (is_illegal_recursion ((*target)->n.sym, gfc_current_ns)
+      && !e->value.compcall.tbp->deferred)
+    gfc_warning (0, "Non-RECURSIVE procedure %qs at %L is possibly calling"
+		 " itself recursively.  Declare it RECURSIVE or use"
+		 " %<-frecursive%>", (*target)->n.sym->name, &e->where);
+
   return true;
 }
 
diff --git a/gcc/fortran/trans-expr.cc b/gcc/fortran/trans-expr.cc
index 76bed9830c4..3b54874cf1f 100644
--- a/gcc/fortran/trans-expr.cc
+++ b/gcc/fortran/trans-expr.cc
@@ -1719,6 +1719,7 @@  gfc_trans_class_init_assign (gfc_code *code)
   tree tmp;
   gfc_se dst,src,memsz;
   gfc_expr *lhs, *rhs, *sz;
+  gfc_component *cmp;
 
   gfc_start_block (&block);
 
@@ -1735,6 +1736,21 @@  gfc_trans_class_init_assign (gfc_code *code)
   /* The _def_init is always scalar.  */
   rhs->rank = 0;
 
+  /* Check def_init for initializers.  If this is a dummy with all default
+     initializer components NULL, return NULL_TREE and use the passed value as
+     required by F2018(8.5.10).  */
+  if (!lhs->ref && lhs->symtree->n.sym->attr.dummy)
+    {
+      cmp = rhs->ref->next->u.c.component->ts.u.derived->components;
+      for (; cmp; cmp = cmp->next)
+	{
+	  if (cmp->initializer)
+	    break;
+	  else if (!cmp->next)
+	    return build_empty_stmt (input_location);
+	}
+    }
+
   if (code->expr1->ts.type == BT_CLASS
       && CLASS_DATA (code->expr1)->attr.dimension)
     {
@@ -12511,11 +12527,14 @@  gfc_trans_assignment_1 (gfc_expr * expr1, gfc_expr * expr2, bool init_flag,
   gfc_add_block_to_block (&body, &lse.pre);
   gfc_add_expr_to_block (&body, tmp);
 
-  /* Add the post blocks to the body.  */
-  if (!l_is_temp)
+  /* Add the post blocks to the body.  Scalar finalization must appear before
+     the post block in case any dellocations are done.  */
+  if (rse.finalblock.head
+      && (!l_is_temp || (expr2->expr_type == EXPR_FUNCTION
+			 && gfc_expr_attr (expr2).elemental)))
     {
-      gfc_add_block_to_block (&rse.finalblock, &rse.post);
       gfc_add_block_to_block (&body, &rse.finalblock);
+      gfc_add_block_to_block (&body, &rse.post);
     }
   else
     gfc_add_block_to_block (&body, &rse.post);
diff --git a/gcc/fortran/trans.cc b/gcc/fortran/trans.cc
index 7f50b16aee9..badad6ae892 100644
--- a/gcc/fortran/trans.cc
+++ b/gcc/fortran/trans.cc
@@ -1624,7 +1624,7 @@  gfc_finalize_tree_expr (gfc_se *se, gfc_symbol *derived,
     }
   else if (derived && gfc_is_finalizable (derived, NULL))
     {
-      if (derived->attr.zero_comp && !rank)
+      if (!derived->components && (!rank || attr.elemental))
 	{
 	  /* Any attempt to assign zero length entities, causes the gimplifier
 	     all manner of problems. Instead, a variable is created to act as
@@ -1675,7 +1675,7 @@  gfc_finalize_tree_expr (gfc_se *se, gfc_symbol *derived,
 					      final_fndecl);
   if (!GFC_DESCRIPTOR_TYPE_P (TREE_TYPE (desc)))
     {
-      if (is_class)
+      if (is_class || attr.elemental)
 	desc = gfc_conv_scalar_to_descriptor (se, desc, attr);
       else
 	{
@@ -1685,7 +1685,7 @@  gfc_finalize_tree_expr (gfc_se *se, gfc_symbol *derived,
 	}
     }
 
-  if (derived && derived->attr.zero_comp)
+  if (derived && !derived->components)
     {
       /* All the conditions below break down for zero length derived types.  */
       tmp = build_call_expr_loc (input_location, final_fndecl, 3,
diff --git a/gcc/testsuite/gfortran.dg/finalize_54.f90 b/gcc/testsuite/gfortran.dg/finalize_54.f90
new file mode 100644
index 00000000000..73d32b1b333
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/finalize_54.f90
@@ -0,0 +1,47 @@ 
+! { dg-do compile }
+! Test the fix for PR113885, where not only was there a gimplifier ICE
+! for a derived type 't' with no components but, with a component, gfortran
+! gave wrong results.
+! Contributed by David Binderman  <dcb314@hotmail.com>
+!
+module types
+  type t
+   contains
+     final :: finalize
+  end type t
+contains
+  pure subroutine finalize(x)
+    type(t), intent(inout) :: x
+  end subroutine finalize
+end module types
+
+subroutine test1(x)
+  use types
+  interface
+     elemental function elem(x)
+       use types
+       type(t), intent(in) :: x
+       type(t) :: elem
+     end function elem
+  end interface
+  type(t) :: x(:)
+  x = elem(x)
+end subroutine test1
+
+subroutine test2(x)
+  use types
+  interface
+     elemental function elem(x)
+       use types
+       type(t), intent(in) :: x
+       type(t) :: elem
+     end function elem
+     elemental function elem2(x, y)
+       use types
+       type(t), intent(in) :: x, y
+       type(t) :: elem2
+     end function elem2
+  end interface
+  type(t) :: x(:)
+  x = elem2(elem(x), elem(x))
+end subroutine test2
diff --git a/gcc/testsuite/gfortran.dg/finalize_55.f90 b/gcc/testsuite/gfortran.dg/finalize_55.f90
new file mode 100644
index 00000000000..fa7e552eea5
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/finalize_55.f90
@@ -0,0 +1,89 @@ 
+! { dg-do run }
+! Test the fix for PR113885, where not only was there a gimplifier ICE
+! for a derived type 't' with no components but this version gave wrong
+! results.
+! Contributed by David Binderman  <dcb314@hotmail.com>
+!
+module types
+  type t
+     integer :: i
+   contains
+     final :: finalize
+  end type t
+  integer :: ctr = 0
+contains
+  impure elemental subroutine finalize(x)
+    type(t), intent(inout) :: x
+    ctr = ctr + 1
+  end subroutine finalize
+end module types
+
+impure elemental function elem(x)
+  use types
+  type(t), intent(in) :: x
+  type(t) :: elem
+  elem%i = x%i + 1
+end function elem
+
+impure elemental function elem2(x, y)
+  use types
+  type(t), intent(in) :: x, y
+  type(t) :: elem2
+  elem2%i = x%i + y%i
+end function elem2
+
+subroutine test1(x)
+  use types
+  interface
+     impure elemental function elem(x)
+       use types
+       type(t), intent(in) :: x
+       type(t) :: elem
+     end function elem
+  end interface
+  type(t) :: x(:)
+  type(t), allocatable :: y(:)
+  y = x
+  x = elem(y)
+end subroutine test1
+
+subroutine test2(x)
+  use types
+  interface
+     impure elemental function elem(x)
+       use types
+       type(t), intent(in) :: x
+       type(t) :: elem
+     end function elem
+     impure elemental function elem2(x, y)
+       use types
+       type(t), intent(in) :: x, y
+       type(t) :: elem2
+     end function elem2
+  end interface
+  type(t) :: x(:)
+  type(t), allocatable :: y(:)
+  y = x
+  x = elem2(elem(y), elem(y))
+end subroutine test2
+
+program test113885
+  use types
+  interface
+    subroutine test1(x)
+      use types
+      type(t) :: x(:)
+    end subroutine
+    subroutine test2(x)
+      use types
+      type(t) :: x(:)
+    end subroutine
+  end interface
+  type(t) :: x(2) = [t(1),t(2)]
+  call test1 (x)
+  if (any (x%i .ne. [2,3])) stop 1
+  if (ctr .ne. 6) stop 2
+  call test2 (x)
+  if (any (x%i .ne. [6,8])) stop 3
+  if (ctr .ne. 16) stop 4
+end
diff --git a/gcc/testsuite/gfortran.dg/finalize_56.f90 b/gcc/testsuite/gfortran.dg/finalize_56.f90
new file mode 100644
index 00000000000..bd350a3bc1c
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/finalize_56.f90
@@ -0,0 +1,168 @@ 
+! { dg-do run }
+! Test the fix for PR110987
+! Segfaulted in runtime, as shown below.
+! Contributed by Kirill Chankin  <chilikin.k@gmail.com>
+! and John Haiducek  <jhaiduce@gmail.com> (comment 5)
+!
+MODULE original_mod
+  IMPLICIT NONE
+
+  TYPE T1_POINTER
+    CLASS(T1), POINTER :: T1
+  END TYPE
+
+  TYPE T1
+    INTEGER N_NEXT
+    CLASS(T1_POINTER), ALLOCATABLE :: NEXT(:)
+  CONTAINS
+    FINAL :: T1_DESTRUCTOR
+    PROCEDURE :: SET_N_NEXT => T1_SET_N_NEXT
+    PROCEDURE :: GET_NEXT => T1_GET_NEXT
+  END TYPE
+
+  INTERFACE T1
+    PROCEDURE T1_CONSTRUCTOR
+  END INTERFACE
+
+  TYPE, EXTENDS(T1) :: T2
+    REAL X
+  CONTAINS
+  END TYPE
+
+  INTERFACE T2
+    PROCEDURE T2_CONSTRUCTOR
+  END INTERFACE
+
+  TYPE, EXTENDS(T1) :: T3
+  CONTAINS
+    FINAL :: T3_DESTRUCTOR
+  END TYPE
+
+  INTERFACE T3
+    PROCEDURE T3_CONSTRUCTOR
+  END INTERFACE
+
+  INTEGER :: COUNTS = 0
+
+CONTAINS
+
+  TYPE(T1) FUNCTION T1_CONSTRUCTOR() RESULT(L)
+    IMPLICIT NONE
+    L%N_NEXT = 0
+  END FUNCTION
+
+  SUBROUTINE T1_DESTRUCTOR(SELF)
+    IMPLICIT NONE
+    TYPE(T1), INTENT(INOUT) :: SELF
+    IF (ALLOCATED(SELF%NEXT)) THEN
+      DEALLOCATE(SELF%NEXT)
+    ENDIF
+  END SUBROUTINE
+
+  SUBROUTINE T3_DESTRUCTOR(SELF)
+    IMPLICIT NONE
+    TYPE(T3), INTENT(IN) :: SELF
+    if (.NOT.ALLOCATED (SELF%NEXT)) COUNTS = COUNTS + 1
+  END SUBROUTINE
+
+  SUBROUTINE T1_SET_N_NEXT(SELF, N_NEXT)
+    IMPLICIT NONE
+    CLASS(T1), INTENT(INOUT) :: SELF
+    INTEGER, INTENT(IN) :: N_NEXT
+    INTEGER I
+    SELF%N_NEXT = N_NEXT
+    ALLOCATE(SELF%NEXT(N_NEXT))
+    DO I = 1, N_NEXT
+      NULLIFY(SELF%NEXT(I)%T1)
+    ENDDO
+  END SUBROUTINE
+
+  FUNCTION T1_GET_NEXT(SELF) RESULT(NEXT)
+    IMPLICIT NONE
+    CLASS(T1), TARGET, INTENT(IN) :: SELF
+    CLASS(T1), POINTER :: NEXT
+    CLASS(T1), POINTER :: L
+    INTEGER I
+    IF (SELF%N_NEXT .GE. 1) THEN
+      NEXT => SELF%NEXT(1)%T1
+      RETURN
+    ENDIF
+    NULLIFY(NEXT)
+  END FUNCTION
+
+  TYPE(T2) FUNCTION T2_CONSTRUCTOR() RESULT(L)
+    IMPLICIT NONE
+    L%T1 = T1()
+    CALL L%T1%SET_N_NEXT(1)
+  END FUNCTION
+
+  TYPE(T3) FUNCTION T3_CONSTRUCTOR() RESULT(L)
+    IMPLICIT NONE
+    L%T1 = T1()
+  END FUNCTION
+
+END MODULE original_mod
+
+module comment5_mod
+  type::parent
+     character(:), allocatable::name
+  end type parent
+  type, extends(parent)::child
+   contains
+     final::child_finalize
+  end type child
+  interface child
+     module procedure new_child
+  end interface child
+  integer :: counts = 0
+
+contains
+
+  type(child) function new_child(name)
+    character(*)::name
+    new_child%name=name
+  end function new_child
+
+  subroutine child_finalize(this)
+    type(child), intent(in)::this
+    counts = counts + 1
+  end subroutine child_finalize
+end module comment5_mod
+
+PROGRAM TEST_PROGRAM
+  call original
+  call comment5
+contains
+  subroutine original
+    USE original_mod
+    IMPLICIT NONE
+    TYPE(T1), TARGET :: X1
+    TYPE(T2), TARGET :: X2
+    TYPE(T3), TARGET :: X3
+    CLASS(T1), POINTER :: L
+    X1 = T1()
+    X2 = T2()
+    X2%NEXT(1)%T1 => X1
+    X3 = T3()
+    CALL X3%SET_N_NEXT(1)
+    X3%NEXT(1)%T1 => X2
+    L => X3
+    DO WHILE (.TRUE.)
+      L => L%GET_NEXT()                 ! Used to segfault here in runtime
+      IF (.NOT. ASSOCIATED(L)) EXIT
+      COUNTS = COUNTS + 1
+    ENDDO
+! Two for T3 finalization and two for associated 'L's
+    IF (COUNTS .NE. 4) STOP 1
+  end subroutine original
+
+  subroutine comment5
+    use comment5_mod, only: child, counts
+    implicit none
+    type(child)::kid
+    kid = child("Name")
+    if (.not.allocated (kid%name)) stop 2
+    if (kid%name .ne. "Name") stop 3
+    if (counts .ne. 2) stop 4
+  end subroutine comment5
+END PROGRAM
diff --git a/gcc/testsuite/gfortran.dg/pr112407a.f90 b/gcc/testsuite/gfortran.dg/pr112407a.f90
new file mode 100644
index 00000000000..81ef8bd55a4
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr112407a.f90
@@ -0,0 +1,70 @@ 
+! { dg-do run }
+! Test of an issue found in the investigation of PR112407
+! Contributed by Tomas Trnka  <trnka@scm.com>
+!
+module m
+  private new_t
+
+  type s
+    procedure(),pointer,nopass :: op
+  end type
+
+  type :: t
+    integer :: i
+    type (s) :: s
+  contains
+    procedure :: new_t
+    procedure :: bar
+    procedure :: add_t
+    generic :: new => new_t, bar
+    generic, public :: assignment(=) => add_t
+    final :: final_t
+  end type
+
+  integer :: i = 0, finals = 0
+
+contains
+  recursive subroutine new_t (arg1, arg2)
+    class(t), intent(out) :: arg1
+    type(t), intent(in)  :: arg2
+    i = i + 1
+
+    print "(a,2i4)", "new_t", arg1%i, arg2%i
+    if (i .ge. 10) return
+
+! According to F2018(8.5.10), arg1 should be undefined on invocation, unless
+! any sub-components are default initialised. gfc used to set arg1%i = 0.
+    if (arg1%i .ne. arg2%i) then
+      arg1%i = arg2%i
+      call arg1%new(arg2)
+    endif
+  end
+
+  subroutine bar(arg)
+    class(t), intent(out) :: arg
+    call arg%new(t(42, s(new_t)))
+  end
+
+  subroutine add_t (arg1, arg2)
+    class(t), intent(out) :: arg1
+    type(t), intent(in)  :: arg2
+    call arg1%new (arg2)
+  end
+
+  impure elemental subroutine final_t (arg1)
+    type(t), intent(in) :: arg1
+    finals = finals + 1
+  end
+end
+
+  use m
+  class(t), allocatable :: x
+  allocate(x)
+  call x%new()                   ! gfortran used to output 10*'new_t'
+  print "(3i4)", x%i, i, finals  !           -||-          0 10 11
+!
+! The other brands output 2*'new_t' + 42 2 3 and now so does gfc :-)
+  if (x%i .ne. 42) stop 1
+  if (i .ne. 2) stop 2
+  if (finals .ne. 3) stop 3
+end
diff --git a/gcc/testsuite/gfortran.dg/pr112407b.f90 b/gcc/testsuite/gfortran.dg/pr112407b.f90
new file mode 100644
index 00000000000..e541825d616
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/pr112407b.f90
@@ -0,0 +1,56 @@ 
+! { dg-do compile }
+! Test of an issue found in the investigation of PR112407
+! Contributed by Tomas Trnka  <trnka@scm.com>
+!
+module m
+  private new_t
+
+  type s
+    procedure(),pointer,nopass :: op
+  end type
+
+  type :: t
+    integer :: i
+    type (s) :: s
+  contains
+    procedure :: new_t
+    procedure :: bar
+    procedure :: add_t
+    generic :: new => new_t, bar
+    generic, public :: assignment(=) => add_t
+    final :: final_t
+  end type
+
+  integer :: i = 0, finals = 0
+
+contains
+  subroutine new_t (arg1, arg2)            ! gfortran didn't detect the recursion
+    class(t), intent(out) :: arg1
+    type(t), intent(in)  :: arg2
+    i = i + 1
+
+    print *, "new_t", arg1%i, arg2%i
+    if (i .ge. 10) return
+
+    if (arg1%i .ne. arg2%i) then
+      arg1%i = arg2%i
+      call arg1%new(arg2)  ! { dg-warning "possibly calling itself recursively" }
+    endif
+  end
+
+  subroutine bar(arg)
+    class(t), intent(out) :: arg
+    call arg%new(t(42, s(new_t)))
+  end
+
+  subroutine add_t (arg1, arg2)
+    class(t), intent(out) :: arg1
+    type(t), intent(in)  :: arg2
+    call arg1%new (arg2)
+  end
+
+  impure elemental subroutine final_t (arg1)
+    type(t), intent(in) :: arg1
+    finals = finals + 1
+  end
+end