/* Expression parser.
   Copyright (C) 2000-2021 Free Software Foundation, Inc.
   Contributed by Andy Vaught

This file is part of GCC.

GCC is free software; you can redistribute it and/or modify it under
the terms of the GNU General Public License as published by the Free
Software Foundation; either version 3, or (at your option) any later
version.

GCC is distributed in the hope that it will be useful, but WITHOUT ANY
WARRANTY; without even the implied warranty of MERCHANTABILITY or
FITNESS FOR A PARTICULAR PURPOSE.  See the GNU General Public License
for more details.

You should have received a copy of the GNU General Public License
along with GCC; see the file COPYING3.  If not see
<http://www.gnu.org/licenses/>.  */

#include "config.h"
#include "system.h"
#include "coretypes.h"
#include "gfortran.h"
#include "arith.h"
#include "match.h"

static const char expression_syntax[] = N_("Syntax error in expression at %C");


/* Match a user-defined operator name.  This is a normal name with a
   few restrictions.  The error_flag controls whether an error is
   raised if 'true' or 'false' are used or not.  */

match
gfc_match_defined_op_name (char *result, int error_flag)
{
  static const char * const badops[] = {
    "and", "or", "not", "eqv", "neqv", "eq", "ne", "ge", "le", "lt", "gt",
      NULL
  };

  char name[GFC_MAX_SYMBOL_LEN + 1];
  locus old_loc;
  match m;
  int i;

  old_loc = gfc_current_locus;

  m = gfc_match (" . %n .", name);
  if (m != MATCH_YES)
    return m;

  /* .true. and .false. have interpretations as constants.  Trying to
     use these as operators will fail at a later time.  */

  if (strcmp (name, "true") == 0 || strcmp (name, "false") == 0)
    {
      if (error_flag)
	goto error;
      gfc_current_locus = old_loc;
      return MATCH_NO;
    }

  for (i = 0; badops[i]; i++)
    if (strcmp (badops[i], name) == 0)
      goto error;

  for (i = 0; name[i]; i++)
    if (!ISALPHA (name[i]))
      {
	gfc_error ("Bad character %qc in OPERATOR name at %C", name[i]);
	return MATCH_ERROR;
      }

  strcpy (result, name);
  return MATCH_YES;

error:
  gfc_error ("The name %qs cannot be used as a defined operator at %C",
	     name);

  gfc_current_locus = old_loc;
  return MATCH_ERROR;
}


/* Match a user defined operator.  The symbol found must be an
   operator already.  */

static match
match_defined_operator (gfc_user_op **result)
{
  char name[GFC_MAX_SYMBOL_LEN + 1];
  match m;

  m = gfc_match_defined_op_name (name, 0);
  if (m != MATCH_YES)
    return m;

  *result = gfc_get_uop (name);
  return MATCH_YES;
}


/* Check to see if the given operator is next on the input.  If this
   is not the case, the parse pointer remains where it was.  */

static int
next_operator (gfc_intrinsic_op t)
{
  gfc_intrinsic_op u;
  locus old_loc;

  old_loc = gfc_current_locus;
  if (gfc_match_intrinsic_op (&u) == MATCH_YES && t == u)
    return 1;

  gfc_current_locus = old_loc;
  return 0;
}


/* Call the INTRINSIC_PARENTHESES function.  This is both
   used explicitly, as below, or by resolve.c to generate
   temporaries.  */

gfc_expr *
gfc_get_parentheses (gfc_expr *e)
{
  gfc_expr *e2;

  e2 = gfc_get_operator_expr (&e->where, INTRINSIC_PARENTHESES, e, NULL);
  e2->ts = e->ts;
  e2->rank = e->rank;

  return e2;
}


/* Match a primary expression.  */

static match
match_primary (gfc_expr **result)
{
  match m;
  gfc_expr *e;

  m = gfc_match_literal_constant (result, 0);
  if (m != MATCH_NO)
    return m;

  m = gfc_match_array_constructor (result);
  if (m != MATCH_NO)
    return m;

  m = gfc_match_rvalue (result);
  if (m != MATCH_NO)
    return m;

  /* Match an expression in parentheses.  */
  if (gfc_match_char ('(') != MATCH_YES)
    return MATCH_NO;

  m = gfc_match_expr (&e);
  if (m == MATCH_NO)
    goto syntax;
  if (m == MATCH_ERROR)
    return m;

  m = gfc_match_char (')');
  if (m == MATCH_NO)
    gfc_error ("Expected a right parenthesis in expression at %C");

  /* Now we have the expression inside the parentheses, build the
     expression pointing to it. By 7.1.7.2, any expression in
     parentheses shall be treated as a data entity.  */
  *result = gfc_get_parentheses (e);

  if (m != MATCH_YES)
    {
      gfc_free_expr (*result);
      return MATCH_ERROR;
    }

  return MATCH_YES;

syntax:
  gfc_error (expression_syntax);
  return MATCH_ERROR;
}


/* Match a level 1 expression.  */

static match
match_level_1 (gfc_expr **result)
{
  gfc_user_op *uop;
  gfc_expr *e, *f;
  locus where;
  match m;

  gfc_gobble_whitespace ();
  where = gfc_current_locus;
  uop = NULL;
  m = match_defined_operator (&uop);
  if (m == MATCH_ERROR)
    return m;

  m = match_primary (&e);
  if (m != MATCH_YES)
    return m;

  if (uop == NULL)
    *result = e;
  else
    {
      f = gfc_get_operator_expr (&where, INTRINSIC_USER, e, NULL);
      f->value.op.uop = uop;
      *result = f;
    }

  return MATCH_YES;
}


/* As a GNU extension we support an expanded level-2 expression syntax.
   Via this extension we support (arbitrary) nesting of unary plus and
   minus operations following unary and binary operators, such as **.
   The grammar of section 7.1.1.3 is effectively rewritten as:

	R704  mult-operand     is level-1-expr [ power-op ext-mult-operand ]
	R704' ext-mult-operand is add-op ext-mult-operand
			       or mult-operand
	R705  add-operand      is add-operand mult-op ext-mult-operand
			       or mult-operand
	R705' ext-add-operand  is add-op ext-add-operand
			       or add-operand
	R706  level-2-expr     is [ level-2-expr ] add-op ext-add-operand
			       or add-operand
 */

static match match_ext_mult_operand (gfc_expr **result);
static match match_ext_add_operand (gfc_expr **result);

static int
match_add_op (void)
{
  if (next_operator (INTRINSIC_MINUS))
    return -1;
  if (next_operator (INTRINSIC_PLUS))
    return 1;
  return 0;
}


static match
match_mult_operand (gfc_expr **result)
{
  /* Workaround -Wmaybe-uninitialized false positive during
     profiledbootstrap by initializing them.  */
  gfc_expr *e = NULL, *exp, *r;
  locus where;
  match m;

  m = match_level_1 (&e);
  if (m != MATCH_YES)
    return m;

  if (!next_operator (INTRINSIC_POWER))
    {
      *result = e;
      return MATCH_YES;
    }

  where = gfc_current_locus;

  m = match_ext_mult_operand (&exp);
  if (m == MATCH_NO)
    gfc_error ("Expected exponent in expression at %C");
  if (m != MATCH_YES)
    {
      gfc_free_expr (e);
      return MATCH_ERROR;
    }

  r = gfc_power (e, exp);
  if (r == NULL)
    {
      gfc_free_expr (e);
      gfc_free_expr (exp);
      return MATCH_ERROR;
    }

  r->where = where;
  *result = r;

  return MATCH_YES;
}


static match
match_ext_mult_operand (gfc_expr **result)
{
  gfc_expr *all, *e;
  locus where;
  match m;
  int i;

  where = gfc_current_locus;
  i = match_add_op ();

  if (i == 0)
    return match_mult_operand (result);

  if (gfc_notification_std (GFC_STD_GNU) == ERROR)
    {
      gfc_error ("Extension: Unary operator following "
		 "arithmetic operator (use parentheses) at %C");
      return MATCH_ERROR;
    }
  else
    gfc_warning (0, "Extension: Unary operator following "
		 "arithmetic operator (use parentheses) at %C");

  m = match_ext_mult_operand (&e);
  if (m != MATCH_YES)
    return m;

  if (i == -1)
    all = gfc_uminus (e);
  else
    all = gfc_uplus (e);

  if (all == NULL)
    {
      gfc_free_expr (e);
      return MATCH_ERROR;
    }

  all->where = where;
  *result = all;
  return MATCH_YES;
}


static match
match_add_operand (gfc_expr **result)
{
  gfc_expr *all, *e, *total;
  locus where, old_loc;
  match m;
  gfc_intrinsic_op i;

  m = match_mult_operand (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      /* Build up a string of products or quotients.  */

      old_loc = gfc_current_locus;

      if (next_operator (INTRINSIC_TIMES))
	i = INTRINSIC_TIMES;
      else
	{
	  if (next_operator (INTRINSIC_DIVIDE))
	    i = INTRINSIC_DIVIDE;
	  else
	    break;
	}

      where = gfc_current_locus;

      m = match_ext_mult_operand (&e);
      if (m == MATCH_NO)
	{
	  gfc_current_locus = old_loc;
	  break;
	}

      if (m == MATCH_ERROR)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      if (i == INTRINSIC_TIMES)
	total = gfc_multiply (all, e);
      else
	total = gfc_divide (all, e);

      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


static match
match_ext_add_operand (gfc_expr **result)
{
  gfc_expr *all, *e;
  locus where;
  match m;
  int i;

  where = gfc_current_locus;
  i = match_add_op ();

  if (i == 0)
    return match_add_operand (result);

  if (gfc_notification_std (GFC_STD_GNU) == ERROR)
    {
      gfc_error ("Extension: Unary operator following "
		 "arithmetic operator (use parentheses) at %C");
      return MATCH_ERROR;
    }
  else
    gfc_warning (0, "Extension: Unary operator following "
		"arithmetic operator (use parentheses) at %C");

  m = match_ext_add_operand (&e);
  if (m != MATCH_YES)
    return m;

  if (i == -1)
    all = gfc_uminus (e);
  else
    all = gfc_uplus (e);

  if (all == NULL)
    {
      gfc_free_expr (e);
      return MATCH_ERROR;
    }

  all->where = where;
  *result = all;
  return MATCH_YES;
}


/* Match a level 2 expression.  */

static match
match_level_2 (gfc_expr **result)
{
  gfc_expr *all, *e, *total;
  locus where;
  match m;
  int i;

  where = gfc_current_locus;
  i = match_add_op ();

  if (i != 0)
    {
      m = match_ext_add_operand (&e);
      if (m == MATCH_NO)
	{
	  gfc_error (expression_syntax);
	  m = MATCH_ERROR;
	}
    }
  else
    m = match_add_operand (&e);

  if (m != MATCH_YES)
    return m;

  if (i == 0)
    all = e;
  else
    {
      if (i == -1)
	all = gfc_uminus (e);
      else
	all = gfc_uplus (e);

      if (all == NULL)
	{
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}
    }

  all->where = where;

  /* Append add-operands to the sum.  */

  for (;;)
    {
      where = gfc_current_locus;
      i = match_add_op ();
      if (i == 0)
	break;

      m = match_ext_add_operand (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      if (i == -1)
	total = gfc_subtract (all, e);
      else
	total = gfc_add (all, e);

      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


/* Match a level three expression.  */

static match
match_level_3 (gfc_expr **result)
{
  gfc_expr *all, *e, *total = NULL;
  locus where;
  match m;

  m = match_level_2 (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      if (!next_operator (INTRINSIC_CONCAT))
	break;

      where = gfc_current_locus;

      m = match_level_2 (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      total = gfc_concat (all, e);
      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


/* Match a level 4 expression.  */

static match
match_level_4 (gfc_expr **result)
{
  gfc_expr *left, *right, *r;
  gfc_intrinsic_op i;
  locus old_loc;
  locus where;
  match m;

  m = match_level_3 (&left);
  if (m != MATCH_YES)
    return m;

  old_loc = gfc_current_locus;

  if (gfc_match_intrinsic_op (&i) != MATCH_YES)
    {
      *result = left;
      return MATCH_YES;
    }

  if (i != INTRINSIC_EQ && i != INTRINSIC_NE && i != INTRINSIC_GE
      && i != INTRINSIC_LE && i != INTRINSIC_LT && i != INTRINSIC_GT
      && i != INTRINSIC_EQ_OS && i != INTRINSIC_NE_OS && i != INTRINSIC_GE_OS
      && i != INTRINSIC_LE_OS && i != INTRINSIC_LT_OS && i != INTRINSIC_GT_OS)
    {
      gfc_current_locus = old_loc;
      *result = left;
      return MATCH_YES;
    }

  where = gfc_current_locus;

  m = match_level_3 (&right);
  if (m == MATCH_NO)
    gfc_error (expression_syntax);
  if (m != MATCH_YES)
    {
      gfc_free_expr (left);
      return MATCH_ERROR;
    }

  switch (i)
    {
    case INTRINSIC_EQ:
    case INTRINSIC_EQ_OS:
      r = gfc_eq (left, right, i);
      break;

    case INTRINSIC_NE:
    case INTRINSIC_NE_OS:
      r = gfc_ne (left, right, i);
      break;

    case INTRINSIC_LT:
    case INTRINSIC_LT_OS:
      r = gfc_lt (left, right, i);
      break;

    case INTRINSIC_LE:
    case INTRINSIC_LE_OS:
      r = gfc_le (left, right, i);
      break;

    case INTRINSIC_GT:
    case INTRINSIC_GT_OS:
      r = gfc_gt (left, right, i);
      break;

    case INTRINSIC_GE:
    case INTRINSIC_GE_OS:
      r = gfc_ge (left, right, i);
      break;

    default:
      gfc_internal_error ("match_level_4(): Bad operator");
    }

  if (r == NULL)
    {
      gfc_free_expr (left);
      gfc_free_expr (right);
      return MATCH_ERROR;
    }

  r->where = where;
  *result = r;

  return MATCH_YES;
}


static match
match_and_operand (gfc_expr **result)
{
  gfc_expr *e, *r;
  locus where;
  match m;
  int i;

  i = next_operator (INTRINSIC_NOT);
  where = gfc_current_locus;

  m = match_level_4 (&e);
  if (m != MATCH_YES)
    return m;

  r = e;
  if (i)
    {
      r = gfc_not (e);
      if (r == NULL)
	{
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}
    }

  r->where = where;
  *result = r;

  return MATCH_YES;
}


static match
match_or_operand (gfc_expr **result)
{
  gfc_expr *all, *e, *total;
  locus where;
  match m;

  m = match_and_operand (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      if (!next_operator (INTRINSIC_AND))
	break;
      where = gfc_current_locus;

      m = match_and_operand (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      total = gfc_and (all, e);
      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


static match
match_equiv_operand (gfc_expr **result)
{
  gfc_expr *all, *e, *total;
  locus where;
  match m;

  m = match_or_operand (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      if (!next_operator (INTRINSIC_OR))
	break;
      where = gfc_current_locus;

      m = match_or_operand (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      total = gfc_or (all, e);
      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


/* Match a level 5 expression.  */

static match
match_level_5 (gfc_expr **result)
{
  gfc_expr *all, *e, *total;
  locus where;
  match m;
  gfc_intrinsic_op i;

  m = match_equiv_operand (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      if (next_operator (INTRINSIC_EQV))
	i = INTRINSIC_EQV;
      else
	{
	  if (next_operator (INTRINSIC_NEQV))
	    i = INTRINSIC_NEQV;
	  else
	    break;
	}

      where = gfc_current_locus;

      m = match_equiv_operand (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      if (i == INTRINSIC_EQV)
	total = gfc_eqv (all, e);
      else
	total = gfc_neqv (all, e);

      if (total == NULL)
	{
	  gfc_free_expr (all);
	  gfc_free_expr (e);
	  return MATCH_ERROR;
	}

      all = total;
      all->where = where;
    }

  *result = all;
  return MATCH_YES;
}


/* Match an expression.  At this level, we are stringing together
   level 5 expressions separated by binary operators.  */

match
gfc_match_expr (gfc_expr **result)
{
  gfc_expr *all, *e;
  gfc_user_op *uop;
  locus where;
  match m;

  m = match_level_5 (&all);
  if (m != MATCH_YES)
    return m;

  for (;;)
    {
      uop = NULL;
      m = match_defined_operator (&uop);
      if (m == MATCH_NO)
	break;
      if (m == MATCH_ERROR)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      where = gfc_current_locus;

      m = match_level_5 (&e);
      if (m == MATCH_NO)
	gfc_error (expression_syntax);
      if (m != MATCH_YES)
	{
	  gfc_free_expr (all);
	  return MATCH_ERROR;
	}

      all = gfc_get_operator_expr (&where, INTRINSIC_USER, all, e);
      all->value.op.uop = uop;
    }

  *result = all;
  return MATCH_YES;
}