[PATCH] PR fortran/69101 -- IEEE_SELECTED_REAL_KIND part I

[Steve Kargl <sgk at troutmask dot apl dot washington dot edu>]

2019-01-04  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/69101
	* expr.c (gfc_check_init_expr): If errors were emitted during
	simplification of ieee_selected_real_kind(), clear any additional
	errors anre return false.
	* simplify.c (simplify_ieee_selected_real_kind): make
        ieee_selected_real_kind() generic in an initialization expression, and
	check for conformance of actual arguments.

 2019-01-04  Steven G. Kargl  <kargl@gcc.gnu.org>

	PR fortran/69101
	* gfortran.dg/ieee/ieee_7.f90: Remove invalid code.
	* gfortran.dg/ieee/pr69101_1.f90: Check for errors in actual
	arguments of ieee_selected_real_kind().
	* gfortran.dg/ieee/pr69101_2.f90: Test -std=f2003.  RADIX was added
	in F2008.

TL;DR version

The attached patch fixes ieee_selected_real_kind (ISRK) when
used in an initialization expression, where either keywords are
mixed up compared to their position or the actual arguments are
not default integer kind.  It does not fix the use of ISRK in
an ordinary expression.

Test on i586-*-freebsd and x86_64-*-freebsd.  OK to commit?


Long version

ISRK is a function with a generic interface.  It is available from
the ieee_arithmetic intrinsic module.  The problem is that the
Fortran standard has specified a generic interface that is not
expressable in Fortran; and hence, gfortran cannot express it in the
file ieee_arithmetic.F90.  If one thinks about the situation, ISRK
is then neither a module procedure nor an intrinsic subprogram.

This patch expands upon the original simplification process when
an ISRK is seen.  It inspects the actual arguments for keywords
and provides a proper ordering.  It checks that each argument, if
present, is a scalar integer entity, and whether -std=F2008 or
later is in effect.  Because gfortran is performing simplification
in an initialization expression, queuing error messages with gfc_error()
is disabled.  Thus, errors are emitted with gfc_error_now().  If one
or more error is emitted, the portion of the patch in expr.c short
circuits simplification to prevent run-on errors.

It is now possible to do 

   program foo
      use ieee_arithmetic, only : isrk => ieee_selected_real_kind
      integer, parameter :: rknd = isrk(radix=2_1, p=6_8, r=200_2)
      print *, rknd
   end program foo

Note, ISRK must be available from the module to allow the renaming
that occurs above, but ideally gfortran should use its machinery
for intrinsic function.

The patch only fixes the use in initialization expression.  If ISRK
appears in a non-initialization expression, gfortran keels over.
Fixes that is Part II of addressing shortcoming with ISRK.

Finally, things are going to even more interesting when F2018's
ieee_real() and ieee_int() are added to gfortran.

-- 
Steve

Index: gcc/fortran/expr.c
===================================================================
--- gcc/fortran/expr.c	(revision 267591)
+++ gcc/fortran/expr.c	(working copy)
@@ -2768,11 +2768,20 @@ gfc_check_init_expr (gfc_expr *e)
 	  mod = sym->generic->sym->from_intmod;
 	if (mod == INTMOD_IEEE_ARITHMETIC || mod == INTMOD_IEEE_EXCEPTIONS)
 	  {
+	    int ecnt;
+
 	    gfc_expr *new_expr = gfc_simplify_ieee_functions (e);
 	    if (new_expr)
 	      {
 		gfc_replace_expr (e, new_expr);
 		t = true;
+		break;
+	      }
+	    gfc_get_errors (NULL, &ecnt);
+	    if (ecnt > 0)
+ 	      {
+		t = false;
+		gfc_clear_error ();
 		break;
 	      }
 	  }
Index: gcc/fortran/simplify.c
===================================================================
--- gcc/fortran/simplify.c	(revision 267591)
+++ gcc/fortran/simplify.c	(working copy)
@@ -8521,25 +8521,129 @@ gfc_simplify_compiler_version (void)
 
 /* Simplification routines for intrinsics of IEEE modules.  */
 
+/* IEEE_SELECTED_REAL_KIND is generic, but cannot be specified in the
+   intrinsic module ieee_arithmetic.mod due to ambiguous interfaces.  When
+   it appears in an initialization expression, the checking must be done
+   here.  */
+
 gfc_expr *
 simplify_ieee_selected_real_kind (gfc_expr *expr)
 {
-  gfc_actual_arglist *arg;
-  gfc_expr *p = NULL, *q = NULL, *rdx = NULL;
+  gfc_actual_arglist *arg0, *arg1, *arg2;
+  gfc_expr *p, *r, *rdx;
 
-  arg = expr->value.function.actual;
-  p = arg->expr;
-  if (arg->next)
+  arg1 = arg2 = NULL;
+  p = r = rdx = NULL;
+
+  arg0 = expr->value.function.actual;
+  if (arg0->next)
+    { 
+      arg1 = arg0->next;
+      if (arg1->next) arg2 = arg1->next;
+    }
+
+  if (!arg0->expr && arg1 && !arg1->expr && arg2 && !arg2->expr)
+   {
+      gfc_error_now ("At least one of P, R, or RADIX must be present in "
+		     "IEEE_SELECTED_REAL_KIND at %C");
+      gfc_clear_error ();
+      return NULL;
+   }
+
+  /* Look at first argument.  */
+  if (!arg0->name || strcmp(arg0->name, "p") == 0)
+    p = arg0->expr;
+  else if (strcmp(arg0->name, "r") == 0)
+    r = arg0->expr;
+  else if (strcmp(arg0->name, "radix") == 0)
+    rdx = arg0->expr;
+  else
+    goto invalid;
+
+  /* Look at second argument, if it exists.  */
+  if (arg1)
     {
-      q = arg->next->expr;
-      if (arg->next->next)
-	rdx = arg->next->next->expr;
+      if (!arg1->name || strcmp(arg1->name, "r") == 0)
+ 	{
+	  if (r)
+	    return NULL;
+	  r = arg1->expr;
+	}
+      else if (strcmp(arg1->name, "p") == 0)
+	{
+	  if (p)
+	    return NULL;
+	  p = arg1->expr;
+	}
+      else if (strcmp(arg1->name, "radix") == 0)
+	{
+	  if (rdx)
+	    return NULL;
+	  rdx = arg1->expr;
+	}
+      else
+	goto invalid;
     }
 
-  /* Currently, if IEEE is supported and this module is built, it means
-     all our floating-point types conform to IEEE. Hence, we simply handle
-     IEEE_SELECTED_REAL_KIND like SELECTED_REAL_KIND.  */
-  return gfc_simplify_selected_real_kind (p, q, rdx);
+  /* Look at third argument, if it exists.  */
+  if (arg2)
+    {
+      if (!arg2->name || strcmp(arg2->name, "radix") == 0)
+	{
+	  if (rdx)
+	    return NULL;
+	  rdx = arg2->expr;
+	}
+      else if (strcmp(arg2->name, "p") == 0)
+	{
+	  if (p)
+	    return NULL;
+	  p = arg2->expr;
+	}
+      else if (strcmp(arg2->name, "r") == 0)
+	{
+	  if (r)
+	    return NULL;
+	  r = arg2->expr;
+	}
+      else
+	goto invalid;
+    }
+
+  /* Check for scalar integer expressions.  */
+  if (p && (p->ts.type != BT_INTEGER || p->rank != 0))
+    goto mismatch;
+
+  if (r && (r->ts.type != BT_INTEGER || r->rank != 0))
+    goto mismatch;
+
+  if (rdx)
+    {
+      if (GFC_STD_F2008 & ~gfc_option.allow_std)
+	{
+	  gfc_error_now ("Fortran 2008: RADIX argument specified in "
+			 "IEEE_SELECTED_REAL_KIND at %C");
+	  return NULL;
+	}
+
+      if (rdx->ts.type != BT_INTEGER || rdx->rank != 0)
+	goto mismatch;
+    }
+
+  return gfc_simplify_selected_real_kind (p, r, rdx);
+
+mismatch:
+
+  gfc_error_now ("Scalar integer argument expected in "
+		 "IEEE_SELECTED_REAL_KIND at %C");
+  return NULL;
+
+invalid:
+
+  /* This should be unreachable.  */
+  gfc_fatal_error ("Invalid uses of IEEE_SELECTED_REAL_KIND at %C");
+  return NULL;
+
 }
 
 gfc_expr *
Index: gcc/testsuite/gfortran.dg/ieee/ieee_7.f90
===================================================================
--- gcc/testsuite/gfortran.dg/ieee/ieee_7.f90	(revision 267591)
+++ gcc/testsuite/gfortran.dg/ieee/ieee_7.f90	(working copy)
@@ -11,7 +11,6 @@
 
   ! Test IEEE_SELECTED_REAL_KIND in specification expressions
 
-  integer(kind=ieee_selected_real_kind()) :: i1
   integer(kind=ieee_selected_real_kind(10)) :: i2
   integer(kind=ieee_selected_real_kind(10,10)) :: i3
   integer(kind=ieee_selected_real_kind(10,10,2)) :: i4
@@ -19,7 +18,6 @@
   ! Test IEEE_SELECTED_REAL_KIND
 
   if (ieee_support_datatype(0.)) then
-    if (ieee_selected_real_kind() /= kind(0.)) STOP 1
     if (ieee_selected_real_kind(0) /= kind(0.)) STOP 2
     if (ieee_selected_real_kind(0,0) /= kind(0.)) STOP 3
     if (ieee_selected_real_kind(0,0,2) /= kind(0.)) STOP 4
Index: gcc/testsuite/gfortran.dg/ieee/pr69101_1.f90
===================================================================
--- gcc/testsuite/gfortran.dg/ieee/pr69101_1.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/ieee/pr69101_1.f90	(working copy)
@@ -0,0 +1,10 @@
+! { dg-do compile }
+program foo
+   use ieee_arithmetic
+   implicit none
+   integer, parameter :: n(3) = [ 1, 2, 3]
+   integer, parameter :: i1 = ieee_selected_real_kind()        ! { dg-error "must be present in" }
+   integer, parameter :: j2 = ieee_selected_real_kind(p=6,p=7) ! { dg-error "has already appeared in" }
+   integer, parameter :: j3 = ieee_selected_real_kind(r=7.)    ! { dg-error "Scalar integer argument" }
+   integer, parameter :: j4 = ieee_selected_real_kind(n)       ! { dg-error "Scalar integer argument" }
+end program foo
Index: gcc/testsuite/gfortran.dg/ieee/pr69101_2.f90
===================================================================
--- gcc/testsuite/gfortran.dg/ieee/pr69101_2.f90	(nonexistent)
+++ gcc/testsuite/gfortran.dg/ieee/pr69101_2.f90	(working copy)
@@ -0,0 +1,7 @@
+! { dg-do compile }
+! { dg-additional-options "-std=f2003" }
+program foo
+   use ieee_arithmetic
+   implicit none
+   integer, parameter :: jr = ieee_selected_real_kind(radix=2) ! { dg-error "RADIX argument" }
+end program foo