[Patch] Fortran: Fix intrinsic null() handling [PR99651]

[Tobias Burnus]

See PR for some analysis. The problem is that during
gfc_intrinsic_func_interface, sym->attr.flavor == FL_PROCEDURE,
hence, attr.intrinsic is not set – but later when parsing
'null()', gfortran calls:

  if (sym->attr.proc != PROC_INTRINSIC
      && !(sym->attr.use_assoc && sym->attr.intrinsic)
      && (!gfc_add_procedure(&sym->attr, PROC_INTRINSIC, sym->name, NULL)
          || !gfc_add_function (&sym->attr, sym->name, NULL)))
    return MATCH_ERROR;

The gfc_add_procedure call fails as 'sym' is use-associated and
may not be modified.

The obvious solution to also set attr.intrinsic for FL_PROCEDURE fails
in multiple ways, e.g. for gfortran.dg/char_length_16.f90 which has:
  CHARACTER (LEN(ITEMVAL)) :: ITEM
  INTRINSIC LEN
the error is that INTRINSIC has been speicified twice. It also affects
the error diagnostic in for generic resolution due to  (I think):
  if (sym->attr.intrinsic)
    return gfc_intrinsic_func_interface (expr, 0);
For gfortran.dg/allocatable_scalar_11.f90 the specific
  ‘array’ argument of ‘allocated’ intrinsic at (1) must be a variable
gets replaced by the generic
  Generic function 'allocated' at (1) is not consistent with a specific 
intrinsic interface

I have now tried it as shown. I think attr.function was not set, but
am not sure. But setting it again for FL_PROCEDURE looks sensible.

I am far from certain that now everything fits together, but I do hope
that nothing fails which did work before ...

OK for mainline? And after waiting a while for GCC 10?

Tobias

PS: I did see once a fail for pr93792.f90 (additional error as 't' in type(t)
is not known) – but I could not reproduce it; the error is valid but later runs
stopped with 'cannot open module file' and did not reach that follow-up error.

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Fortran: Fix intrinsic null() handling [PR99651]

gcc/fortran/ChangeLog:

	PR fortran/99651
	* intrinsic.c (gfc_intrinsic_func_interface): Set
	attr.proc = PROC_INTRINSIC if FL_PROCEDURE.

gcc/testsuite/ChangeLog:

	PR fortran/99651
	* gfortran.dg/null_11.f90: New test.

 gcc/fortran/intrinsic.c               |  5 +++++
 gcc/testsuite/gfortran.dg/null_11.f90 | 16 ++++++++++++++++
 2 files changed, 21 insertions(+)

diff --git a/gcc/fortran/intrinsic.c b/gcc/fortran/intrinsic.c
index e68eff8bdbb..17fd92eb462 100644
--- a/gcc/fortran/intrinsic.c
+++ b/gcc/fortran/intrinsic.c
@@ -5071,6 +5071,11 @@ got_specific:
       sym->attr.intrinsic = 1;
       sym->attr.flavor = FL_PROCEDURE;
     }
+  if (sym->attr.flavor == FL_PROCEDURE)
+    {
+      sym->attr.function = 1;
+      sym->attr.proc = PROC_INTRINSIC;
+    }
 
   if (!sym->module)
     gfc_intrinsic_symbol (sym);
diff --git a/gcc/testsuite/gfortran.dg/null_11.f90 b/gcc/testsuite/gfortran.dg/null_11.f90
new file mode 100644
index 00000000000..040cc260b5d
--- /dev/null
+++ b/gcc/testsuite/gfortran.dg/null_11.f90
@@ -0,0 +1,16 @@
+! { dg-do compile }
+!
+! PR fortran/99651
+!
+module m
+    type :: CHAR_STAR
+      character(len=1),dimension(:),pointer :: ptr
+    end type
+    type(CHAR_STAR), parameter ::CHAR_STAR_NULL = CHAR_STAR(NULL())
+end module m
+
+use m
+type typeNode
+    type(typeNode),   pointer       :: Next => null()
+end type typeNode
+end