/**
 * mds — A micro-display server
 * Copyright © 2014  Mattias Andrée (maandree@member.fsf.org)
 * 
 * This program 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 of the License, or
 * (at your option) any later version.
 * 
 * This program 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 this program.  If not, see <http://www.gnu.org/licenses/>.
 */
#include "compile-layout.h"
/* TODO add call stack */

#include "include-stack.h"
#include "builtin-functions.h"
#include "string.h"
#include "variables.h"
#include "callables.h"

#include <stdlib.h>
#include <errno.h>
#include <string.h>



/**
 * This process's value for `mds_kbdc_tree_t.processed`
 */
#define PROCESS_LEVEL  6

/**
 * Tree type constant shortener
 */
#define C(TYPE)  MDS_KBDC_TREE_TYPE_##TYPE

/**
 * Add an error with “included from here”-notes to the error list
 * 
 * @param  NODE:const mds_kbdc_tree_t*    The node the triggered the error
 * @param  SEVERITY:identifier            * in `MDS_KBDC_PARSE_ERROR_*` to indicate severity
 * @param  ...:const char*, ...           Error description format string and arguments
 * @scope  error:mds_kbdc_parse_error_t*  Variable where the new error will be stored
 */
#define NEW_ERROR(NODE, SEVERITY, ...)					\
  NEW_ERROR_WITH_INCLUDES(NODE, includes_ptr, SEVERITY, __VA_ARGS__)

/**
 * Beginning of failure clause
 */
#define FAIL_BEGIN  pfail: saved_errno = errno

/**
 * End of failure clause
 */
#define FAIL_END  return errno = saved_errno, -1



/**
 * Variable whether the latest created error is stored
 */
static mds_kbdc_parse_error_t* error;

/**
 * The parameter of `compile_layout`
 */
static mds_kbdc_parsed_t* restrict result;

/**
 * 3:   `return` is being processed
 * 2:    `break` is being processed
 * 1: `continue` is being processed
 * 0:    Neither is being processed
 */
static int break_level = 0;

/**
 * Whether a second variant has already been encountered
 */
static int multiple_variants = 0;

/**
 * The previous value-statement, which has no effect
 * if we can find another value statemnt that is
 * sure to be evaluated
 * 
 * (We will not look too hard.)
 */
static mds_kbdc_tree_t* last_value_statement = NULL;

/**
 * Address of the current return value
 */
static char32_t** current_return_value = NULL;

/**
 * Whether ‘\set/3’ has been called
 */
static int have_side_effect = 0;



/**
 * Compile a subtree
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_subtree(mds_kbdc_tree_t* restrict tree);

/**
 * Check that a function used in a part of a literal is defined
 * 
 * @param  tree     The statement where the literal is located
 * @param  raw      The beginning of the function call in the literal
 * @param  lineoff  The offset on the line where the function call in the literal beings
 * @param  end      Output parameter for the end of the function call
 * @param  rc       Success status output parameter: zero on success,
 *                  -1 on error, 1 if an undefined function is used
 */
static void check_function_call(const mds_kbdc_tree_t* restrict tree, const char* restrict raw,
				size_t lineoff, const char* restrict* restrict end, int* restrict rc);

/**
 * Parse an argument in a function call
 * 
 * @param   tree     The statement where the function call appear
 * @param   raw      The beginning of the argument for the function call
 * @param   lineoff  The offset for `raw` on line in which it appears
 * @param   end      Output parameter for the end of the argument
 * @param   value    Output parameter for the value to which the argument evaulates
 * @return           Zero on success, -1 on error
 */
static int parse_function_argument(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff,
				   const char* restrict* restrict end, char32_t** restrict value);



/*** Macro-, function- and variable-support, string-parsing and value- and mapping-compilation. ***/
/*                           (Basically everything except tree-walking.)                          */


/**
 * Assign a value to a variable, and define or shadow it in the process
 * 
 * @param   variable                  The variable index
 * @param   string                    The variable's new value, must be `NULL` iff `value != NULL`
 * @param   value                     The variable's new value, must be `NULL` iff `string != NULL`
 * @param   statement                 The statement where the variable is assigned, may be `NULL`
 * @param   lineoff                   The offset of the line for where the string selecting the variable begins
 * @param   possibile_shadow_attempt  Whether `statement` is of a type that does not shadow variables,
 *                                    but could easily be mistaked for one that does
 * @return                            Zero on success, -1 on error
 */
static int let(size_t variable, const char32_t* restrict string, const mds_kbdc_tree_t* restrict value,
	       mds_kbdc_tree_t* restrict statement, size_t lineoff, int possibile_shadow_attempt)
{
  mds_kbdc_tree_t* tree = NULL;
  int saved_errno;
  
  /* Warn if this is a possible shadow attempt. */
  if (possibile_shadow_attempt && variables_let_will_override(variable) &&
      statement && (statement->processed != PROCESS_LEVEL))
    {
      statement->processed = PROCESS_LEVEL;
      NEW_ERROR(statement, WARNING, "does not shadow existing definition");
      error->start = lineoff;
      error->end = lineoff + (size_t)snprintf(NULL, 0, "\\%zu", variable);
    }
  
  /* Duplicate value. */
  if (value)
    fail_if ((tree = mds_kbdc_tree_dup(value), tree == NULL));
  if (value == NULL)
    {
      fail_if ((tree = mds_kbdc_tree_create(C(COMPILED_STRING)), tree == NULL));
      tree->compiled_string.string = string_dup(string);
      fail_if (tree->compiled_string.string == NULL);
    }
  
  /* Assign variable. */
  fail_if (variables_let(variable, tree));
  return 0;
  FAIL_BEGIN;
  mds_kbdc_tree_free(tree);
  FAIL_END;
}


/**
 * Check that a call to set/3 or get/2 is valid
 * 
 * @param   tree          The statement from where the function is called
 * @param   is_set        Whether a call to set/3 is being checked
 * @param   variable_arg  The first argument
 * @param   index_arg     The second argument
 * @param   start         The offset on the line where the function call begins
 * @param   end           The offset on the line where the function call ends
 * @return                Zero on success, -1 on error, 1 if the call is invalid
 */
static int check_set_3_get_2_call(mds_kbdc_tree_t* restrict tree, int is_set, const char32_t* variable_arg,
				  const char32_t* index_arg, size_t start, size_t end)
{
#define F  (is_set ? "set/3" : "get/2")
#define FUN_ERROR(...)			\
  do					\
    {					\
      NEW_ERROR(__VA_ARGS__);		\
      error->start = start;		\
      error->end = end;			\
      return 1;				\
    }					\
  while(0);
  
  mds_kbdc_tree_t* variable;
  mds_kbdc_tree_t* element;
  size_t index;
  
  if ((variable_arg[0] <= 0) || (variable_arg[1] != -1))
    FUN_ERROR(tree, ERROR, "first argument in call to function ‘%s’ must be a variable index", F);
  
  if ((index_arg[0] < 0) || (index_arg[1] != -1))
    FUN_ERROR(tree, ERROR, "second argument in call to function ‘%s’ must be an element index", F);
  
  variable = variables_get((size_t)*variable_arg);
  if (variable == NULL)
    FUN_ERROR(tree, ERROR, "‘\\%zu’ is not declared", (size_t)*variable_arg);
  if (variable->type != C(ARRAY))
    FUN_ERROR(tree, ERROR, "‘\\%zu’ is not an array", (size_t)*variable_arg);
  
  index = (size_t)*index_arg;
  element = variable->array.elements;
  while (element && index--)
    element = element->next;
  
  if (element == NULL)
    FUN_ERROR(tree, ERROR, "‘\\%zu’ does not hold %zu elements", (size_t)*variable_arg, (size_t)*index_arg);
  
  return 0;
 pfail:
  return -1;
#undef FUN_ERROR
#undef F
}


/**
 * Call a function
 * 
 * @param   tree          The statement from where the function is called
 * @param   name          The name of the function, suffixless
 * @param   arguments     The arguments to pass to the function, `NULL`-terminated
 * @param   start         The offset on the line where the function call begins
 * @param   end           The offset on the line where the function call ends
 * @param   return_value  Output parameter for the return value, `NULL` if the
 *                        function did not return, was not defined or otherwise
 *                        invoked an error, which is true will be reported to the
 *                        user from this function and the statement will be marked
 *                        as containing an error
 * @return                Zero on success, -1 on error
 */
static int call_function(mds_kbdc_tree_t* restrict tree, const char* restrict name,
			 const char32_t** restrict arguments, size_t start, size_t end,
			 char32_t** restrict return_value)
{
#define FUN_ERROR(...)					\
  do							\
    {							\
      NEW_ERROR(__VA_ARGS__);				\
      error->start = start;				\
      error->end = end;					\
      tree->processed = PROCESS_LEVEL;			\
      free(*return_value), *return_value = NULL;	\
      goto done;					\
    }							\
  while(0);
  
  size_t i, arg_count = 0, empty_count = 0;
  char32_t** old_return_value;
  mds_kbdc_tree_function_t* function = NULL;
  mds_kbdc_include_stack_t* function_include_stack = NULL;
  mds_kbdc_include_stack_t* our_include_stack = NULL;
  int r, is_set, builtin, saved_errno;
  
  /* Count the number of arguments we have. */
  while (arguments[arg_count])
    arg_count++;
  
  /* Push return-stack. */
  *return_value = NULL;
  old_return_value = current_return_value;
  current_return_value = return_value;
  
  /* Get function definition. */
  builtin = builtin_function_defined(name, arg_count);
  if (builtin == 0)
    callables_get(name, arg_count, (mds_kbdc_tree_t**)&function, &function_include_stack);
  if ((builtin == 0) && (function == NULL))
    FUN_ERROR(tree, ERROR, "function ‘%s/%zu’ has not been defined yet", name, arg_count);
  
  
  /* Call non-builtin function. */
  if (builtin == 0)
    {
      /* Push call stack and set parameters. */
      variables_stack_push();
      for (i = 0; i < arg_count; i++)
	fail_if (let(i, arguments[i], NULL, NULL, 0, 0));
      
      /* Switch include-stack to the function's. */
      fail_if ((our_include_stack = mds_kbdc_include_stack_save(), our_include_stack == NULL));
      fail_if (mds_kbdc_include_stack_restore(function_include_stack));
      
      /* Call the function. */
      fail_if (compile_subtree(function->inner));
      
      /* Switch back the include-stack to ours. */
      fail_if (mds_kbdc_include_stack_restore(our_include_stack));
      mds_kbdc_include_stack_free(our_include_stack), our_include_stack = NULL;
      
      /* Pop call stack. */
      variables_stack_pop();
      
      /* Check that the function returned a value. */
      if (*return_value == NULL)
	FUN_ERROR(tree, ERROR, "function ‘%s/%zu’ did not return a value", name, arg_count);
      
      goto done;
    }
  
  
  /* Call builtin function. */
  
  /* Check argument sanity. */
  is_set = (arg_count == 3) && !strcmp(name, "set");
  if (is_set || ((arg_count == 2) && !strcmp(name, "get")))
    {
      fail_if ((r = check_set_3_get_2_call(tree, is_set, arguments[0], arguments[1], start, end), r < 0));
      if (r)
	{
	  tree->processed = PROCESS_LEVEL;
	  free(*return_value), *return_value = NULL;
	  goto done;
	}
    }
  else
    {
      for (i = 0; i < arg_count; i++)
	empty_count += string_length(arguments[i]) == 0;
      if (empty_count && (empty_count != arg_count))
	FUN_ERROR(tree, ERROR,
		  "built-in function ‘%s/%zu’ requires that either none of"
		  " the arguments are empty strings or that all of them are",
		  name, arg_count);
    }
  
  /* Call the function. */
  *return_value = builtin_function_invoke(name, arg_count, arguments);
  fail_if (*return_value == NULL);
  have_side_effect |= is_set;
  
  
 done:
  /* Pop return-stack. */
  current_return_value = old_return_value;
  return 0;
  
  FAIL_BEGIN;
  mds_kbdc_include_stack_free(our_include_stack);
  free(*return_value), *return_value = NULL;
  current_return_value = old_return_value;
  FAIL_END;
#undef FUN_ERROR
}


/**
 * Parse a function call escape
 * 
 * @param   tree     The statement where the escape is located
 * @param   raw      The escape to parse
 * @param   lineoff  The offset on the line where the escape beings
 * @param   escape   Will be set to zero if the escape ended,
 *                   will be set to anything but zero otherwise
 * @param   end      Output parameter for the end of the escape
 * @return           The text the escape represents, `NULL` on error
 */
static char32_t* parse_function_call(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff,
				     int* restrict escape, const char* restrict* restrict end)
{
#define R(LOWER, UPPER)  (((LOWER) <= c) && (c <= (UPPER)))
#define GROW_ARGS									\
  if (arguments_ptr == arguments_size)							\
    fail_if (xxrealloc(old_arguments, arguments, arguments_size += 4, char32_t*))
  
  const char* restrict bracket = raw + 1;
  char32_t* rc = NULL;
  const char32_t** restrict arguments_;
  char32_t** restrict arguments = NULL;
  char32_t** restrict old_arguments = NULL;
  size_t arguments_ptr = 0, arguments_size = 0;
  char* restrict name;
  char c;
  int r, saved_errno;
  
  /* Find the opening bracket associated with the function call and validate the escape. */
  while ((c = *bracket++))
    if ((c == '_') || R('0', '9') || R('a', 'z') || R('A', 'Z'));
    else if (c == '(')
      break;
    else
      {
	*end = --bracket;
	NEW_ERROR(tree, ERROR, "invalid escape");
	goto error;
      }
  
  /* Copy the name of the function. */
  name = alloca((size_t)(bracket - raw) * sizeof(char));
  memcpy(name, raw + 1, (size_t)(bracket - raw - 1) * sizeof(char));
  name[bracket - raw - 1] = 0;
  
  /* Get arguments. */
  for (*end = ++bracket;;)
    {
      while (**end == ' ')
	(*end)++;
      GROW_ARGS;
      arguments[arguments_ptr] = NULL;
      if (**end == ')')
	{
	  arguments_ptr++;
	  break;
	}
      r = parse_function_argument(tree, *end, lineoff + (size_t)(*end - raw), end, arguments + arguments_ptr++);
      fail_if (r < 0);
    }
  
  /* Call the function. */
  if (tree->processed == PROCESS_LEVEL)
    goto stop;
  arguments_ = alloca(arguments_ptr * sizeof(const char32_t*));
  memcpy(arguments_, arguments, arguments_ptr * sizeof(const char32_t*));
  fail_if (call_function(tree, name, arguments_, lineoff, lineoff + (size_t)(*end - raw), &rc));
  if (rc == NULL)
    goto stop;
  
  while (arguments_ptr--)
    free(arguments[arguments_ptr]);
  free(arguments);
  *escape = (**end == ')') ? 0 : 1;
  if (*escape == 0)
    (*end)++;
  return rc;
  
 error:
  error->start = lineoff;
  error->end = lineoff + (size_t)(*end - raw);
 stop:
  *escape = 0;
  tree->processed = PROCESS_LEVEL;
  fail_if (xmalloc(rc, 1, char32_t));
  return *rc = -1, rc;
  
 pfail:
  saved_errno = errno;
  free(rc);
  if (old_arguments)
    arguments = old_arguments;
  while (arguments_ptr--)
    free(arguments[arguments_ptr]);
  free(arguments);
  return errno = saved_errno, NULL;
#undef GROW_ARGS
#undef R
}


/**
 * Check that all functions used in a part of a literal are defined
 * 
 * @param   tree     The statement where the literal is located
 * @param   raw      The beginning of the part of the literal to check
 * @param   lineoff  The offset on the line where the part of the literal beings
 * @param   end      Output parameter for the part of the literal
 * @param   rc       Success status output parameter: zero on success,
 *                   -1 on error, 1 if an undefined function is used
 * @return           The number of arguments the part of the literal contains
 */
static size_t check_function_calls_in_literal_(const mds_kbdc_tree_t* restrict tree,
					       const char* restrict raw, size_t lineoff,
					       const char* restrict* restrict end, int* restrict rc)
{
#define R(LOWER, UPPER)  (((LOWER) <= c) && (c <= (UPPER)))
  const char* restrict raw_ = raw;
  size_t count = 0;
  int space = 1, quote = 0, escape = 0;
  char c;
  
  while ((c = *raw++))
    {
      if ((c != ' ') && space)
	space = 0, count++;
      
      if (escape)
	{
	  escape = 0;
	  if ((c == '_') || R('a', 'z') || R('A', 'Z'))
	    if (check_function_call(tree, raw - 2, lineoff + (size_t)(raw - 2 - raw_), &raw, rc), *rc < 0)
	      break;
	}
      else if (c == '\\')  escape = 1;
      else if (c == '"')   quote ^= 1;
      else if (!quote)
	{
	  space = (c == ' ');
	  if (c == ')')
	    break;
	}
    }
  
  *end = raw;
  return count;
#undef R
}


/**
 * Check that a function used in a part of a literal is defined
 * 
 * @param  tree     The statement where the literal is located
 * @param  raw      The beginning of the function call in the literal
 * @param  lineoff  The offset on the line where the function call in the literal beings
 * @param  end      Output parameter for the end of the function call
 * @param  rc       Success status output parameter: zero on success,
 *                  -1 on error, 1 if an undefined function is used
 */
static void check_function_call(const mds_kbdc_tree_t* restrict tree, const char* restrict raw,
				size_t lineoff, const char* restrict* restrict end, int* restrict rc)
{
  mds_kbdc_tree_t* function = NULL;
  mds_kbdc_include_stack_t* _function_include_stack;
  char* restrict bracket = strchr(raw, '(');
  char* restrict name;
  size_t arg_count;
  
  /* Check that it is a function call by check that it has an opening bracket. */
  if (bracket == NULL)
    {
      *end = raw + strlen(raw);
      return;
    }
  
  /* Copy the name of the function. */
  name = alloca((size_t)(bracket - raw) * sizeof(char));
  memcpy(name, raw + 1, (size_t)(bracket - raw - 1) * sizeof(char));
  name[bracket++ - raw - 1] = 0;
  
  /* Get the number of arguments used, and check function calls there too. */
  arg_count = check_function_calls_in_literal_(tree, bracket, lineoff + (size_t)(bracket - raw), end, rc);
  if (*rc < 0)  return;
  
  /* Check that the function is defined. */
  if (builtin_function_defined(name, arg_count))
    return;
  callables_get(name, arg_count, &function, &_function_include_stack);
  if (function != NULL)
    return;
  *rc |= 1;
  NEW_ERROR(tree, ERROR, "function ‘%s/%zu’ has not been defined yet", name, arg_count);
  error->start = lineoff;
  error->end = lineoff + (size_t)(*end - raw);
  return;
  
 pfail:
  *rc |= -1;
}


/**
 * Check that all functions used in a literal are defined
 * 
 * @param   tree     The statement where the literal is located
 * @param   raw      The literal to check
 * @param   lineoff  The offset on the line where the literal beings
 * @return           Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls_in_literal(const mds_kbdc_tree_t* restrict tree,
					   const char* restrict raw, size_t lineoff)
{
  int rc = 0;
  (void) check_function_calls_in_literal_(tree, raw, lineoff, &raw, &rc);
  return rc;
}


/**
 * Parse an escape, variable dereference or function call
 * 
 * @param   tree     The statement where the escape is located
 * @param   raw      The escape to parse
 * @param   lineoff  The offset on the line where the escape beings
 * @param   escape   Will be set to zero if the escape ended,
 *                   will be set to anything but zero otherwise
 * @param   end      Output parameter for the end of the escape
 * @return           The text the escape represents, `NULL` on error
 */
static char32_t* parse_escape(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff,
			      int* restrict escape, const char* restrict* restrict end)
{
#define R(LOWER, UPPER)         (((LOWER) <= c) && (c <= (UPPER)))
#define CR(COND, LOWER, UPPER)  ((COND) && ((LOWER) <= c) && (c <= (UPPER)))
#define VARIABLE                (int)(raw - raw_) - (c == '.'), raw_
#define RETURN_ERROR(...)					\
  do								\
    {								\
      NEW_ERROR(__VA_ARGS__);					\
      error->start = lineoff;					\
      error->end = lineoff + (size_t)(raw - raw_);		\
      tree->processed = PROCESS_LEVEL;				\
      *escape = 0;						\
      if (rc)							\
	goto done;						\
      fail_if ((rc = malloc(sizeof(char32_t)), rc == NULL));	\
      *rc = -1;							\
      goto done;						\
    }								\
  while (0)
  
  const char* restrict raw_ = raw++;
  char c = *raw++;
  uintmax_t numbuf = 0;
  char32_t* rc = NULL;
  mds_kbdc_tree_t* value;
  int have = 0, saved_errno;
  
  
  /* Get escape type. */
  if (c == '0')
    /* Octal representation. */
    *escape = 8;
  else if (c == 'u')
    /* Hexadecimal representation. */
    *escape = 16;
  else if (R('1', '9'))
    /* Variable dereference. */
    *escape = 10;
  else if ((c == '_') || R('a', 'z') || R('A', 'Z'))
    /* Function call. */
    *escape = 100;
  else
    RETURN_ERROR(tree, ERROR, "invalid escape");
  
  
  /* Read escape. */
  if (*escape == 100)
    /* Function call. */
    return parse_function_call(tree, raw_, lineoff, escape, end);
  /* Octal or hexadecimal representation, or variable dereference. */
  for (; (c = *raw++) && (c != '.'); have = 1)
    if      (CR(*escape ==  8, '0', '7'))  numbuf =  8 * numbuf + (c & 15);
    else if (CR(*escape == 16, '0', '9'))  numbuf = 16 * numbuf + (c & 15);
    else if (CR(*escape == 16, 'a', 'f'))  numbuf = 16 * numbuf + (c & 15) + 9;
    else if (CR(*escape == 16, 'A', 'F'))  numbuf = 16 * numbuf + (c & 15) + 9;
    else if (CR(*escape == 10, '0', '9'))  numbuf = 10 * numbuf + (c & 15);
    else
      {
	raw--;
	break;
      }
  if (have == 0)
    RETURN_ERROR(tree, ERROR, "invalid escape");
  
  
  /* Evaluate escape. */
  if (*escape == 10)
    {
      /* Variable dereference. */
      if (value = variables_get((size_t)numbuf), value == NULL)
	RETURN_ERROR(tree, ERROR, "variable ‘%.*s’ is not defined", VARIABLE);
      if (value->type == C(ARRAY))
	RETURN_ERROR(tree, ERROR, "variable ‘%.*s’ is an array", VARIABLE);
      if (value->type != C(COMPILED_STRING))
	NEW_ERROR(tree, INTERNAL_ERROR, "variable ‘%.*s’ is of impossible type", VARIABLE);
      fail_if ((rc = string_dup(tree->compiled_string.string), rc == NULL));
    }
  else
    {
      /* Octal or hexadecimal representation. */
      fail_if ((rc = malloc(2 * sizeof(char32_t)), rc == NULL));
      rc[0] = (char32_t)numbuf, rc[1] = -1;
    }
  
  
 done:
  *escape = 0;
  *end = raw;
  return rc;
 pfail:
  saved_errno = errno;
  free(rc);
  return errno = saved_errno, NULL;
#undef RETURN_ERROR
#undef VARIABLE
#undef CR
#undef R
}


/**
 * Parse a quoted string
 * 
 * @param   tree     The statement where the string is located
 * @param   raw      The string to parse
 * @param   lineoff  The offset on the line where the string beings
 * @return           The string as pure text, `NULL` on error
 */
static char32_t* parse_quoted_string(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff)
{
#define GROW_BUF								\
  if (buf_ptr == buf_size)							\
    fail_if (xxrealloc(old_buf, buf, buf_size ? (buf_size <<= 1) : 16, char))
#define COPY							\
  n = string_length(subrc);					\
  if (rc_ptr + n > rc_size)					\
    fail_if (xxrealloc(old_rc, rc, rc_ptr + n, char32_t));	\
  memcpy(rc + rc_ptr, subrc, n * sizeof(char32_t));		\
  free(subrc), subrc = NULL
#define STORE							\
  GROW_BUF;							\
  buf[buf_ptr] = '\0', buf_ptr = 0;				\
  fail_if ((subrc = string_decode(buf), subrc == NULL));	\
  COPY
#define CHAR_ERROR(...)					\
  do							\
    {							\
      NEW_ERROR(__VA_ARGS__);				\
      error->end = lineoff + (size_t)(raw - raw_);	\
      error->start = error->end - 1;			\
    }							\
  while (0)
  
  const char* restrict raw_ = raw;
  char32_t* restrict subrc = NULL;
  char32_t* restrict rc = NULL;
  char32_t* restrict old_rc = NULL;
  char* restrict buf = NULL;
  char* restrict old_buf = NULL;
  size_t rc_ptr = 0, rc_size = 0, n;
  size_t buf_ptr = 0, buf_size = 0;
  int quote = 0, escape = 0;
  char c;
  int saved_errno;
  
  /* Parse the string. */
  while ((c = *raw++))
    if (escape && quote && strchr("()[]{}<>\"\\,", c))
      {
	/* Buffer UTF-8 text for convertion to UTF-32. */
	GROW_BUF;
	buf[buf_ptr++] = c;
	escape = 0;
      }
    else if (escape)
      {
	/* Parse escape. */
	raw -= 2, subrc = parse_escape(tree, raw, lineoff + (size_t)(raw - raw_), &escape, &raw);
	fail_if (subrc == NULL);
	COPY;
      }
    else if (c == '"')
      {
	/* Close or open quote, of it got closed, convert the buffered UTF-8 text to UTF-32. */
	if (quote ^= 1)  continue;
	if ((quote == 1) && (raw != raw_ + 1))
	  CHAR_ERROR(tree, WARNING, "strings should either be unquoted or unclosed in one large quoted");
	STORE;
      }
    else if (c == '\\')
      {
	/* Convert the buffered UTF-8 text to UTF-32, and start an escape. */
	STORE;
	escape = 1;
      }
    else if ((quote == 0) && (tree->processed != PROCESS_LEVEL))
      {
	/* Only escapes may be used without quotes, if the string contains quotes. */
	if (*raw_ == '"')
	  CHAR_ERROR(tree, ERROR, "only escapes may be outside quotes in quoted strings");
	else
	  CHAR_ERROR(tree, ERROR, "mixing numericals and escapes is not allowed");
	tree->processed = PROCESS_LEVEL;
      }
    else
      {
	/* Buffer UTF-8 text for convertion to UTF-32. */
	GROW_BUF;
	buf[buf_ptr++] = c;
      }
  
  /* Check that no escape is incomplete. */
  if (escape && (tree->processed != PROCESS_LEVEL))
    {
      NEW_ERROR(tree, ERROR, "incomplete escape");
      error->start = lineoff + (size_t)(strrchr(raw_, '\\') - raw);
      error->end = lineoff + strlen(raw_);
      tree->processed = PROCESS_LEVEL;
    }
  
  /* Check that the quote is complete. */
  if (quote && (tree->processed != PROCESS_LEVEL))
    {
      NEW_ERROR(tree, ERROR, "quote is not closed");
      error->start = lineoff;
      error->end = lineoff + strlen(raw_);
      tree->processed = PROCESS_LEVEL;
    }
  
  /* Shrink or grow to string to its minimal size, and -1-terminate it. */
  fail_if (xxrealloc(old_rc, rc, rc_ptr + 1, char32_t));
  rc[rc_ptr] = -1;
  
  free(buf);
  return rc;
 pfail:
  saved_errno = errno;
  free(subrc);
  free(old_rc);
  free(old_buf);
  free(rc);
  free(buf);
  return errno = saved_errno, NULL;
#undef CHAR_ERROR
#undef STORE
#undef COPY
#undef GROW_BUF
}


/**
 * Parse am unquoted string
 * 
 * @param   tree     The statement where the string is located
 * @param   raw      The string to parse
 * @param   lineoff  The offset on the line where the string beings
 * @return           The string as pure text, `NULL` on error
 */
static char32_t* parse_unquoted_string(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff)
{
#define R(LOWER, UPPER)  (((LOWER) <= c) && (c <= (UPPER)))
#define CHAR_ERROR(...)					\
  do							\
    {							\
      NEW_ERROR(__VA_ARGS__);				\
      error->end = lineoff + (size_t)(raw - raw_);	\
      error->start = error->end - 1;			\
      tree->processed = PROCESS_LEVEL;			\
      goto done;					\
    }							\
  while (0)
  
  const char* restrict raw_ = raw;
  char32_t* rc;
  char32_t buf = 0;
  char c;
  
  while ((c = *raw++))
    if (R('0', '9'))     buf = 10 * buf + (c & 15);
    else if (c == '\\')  CHAR_ERROR(tree, ERROR, "mixing numericals and escapes is not allowed");
    else if (c == '"')   CHAR_ERROR(tree, ERROR, "mixing numericals and quotes is not allowed");
    else                 CHAR_ERROR(tree, ERROR, "stray ‘%c’", c);
  
 done:
  fail_if ((rc = malloc(2 * sizeof(char32_t)), rc == NULL));
  return rc[0] = buf, rc[1] = -1, rc;
  
 pfail:
  return NULL;
#undef CHAR_ERROR
#undef R
}


/**
 * Parse a string
 * 
 * @param   tree     The statement where the string is located
 * @param   raw      The string to parse
 * @param   lineoff  The offset on the line where the string beings
 * @return           The string as pure text, `NULL` on error
 */
static char32_t* parse_string(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff)
{
  mds_kbdc_tree_t* old_last_value_statement = last_value_statement;
  char32_t* rc = (strchr("\"\\", *raw) ? parse_quoted_string : parse_unquoted_string)(tree, raw, lineoff);
  return last_value_statement = old_last_value_statement, rc;
}


/**
 * Parse a key-combination string
 * 
 * @param   tree     The statement where the string is located
 * @param   raw      The string to parse
 * @param   lineoff  The offset on the line where the string beings
 * @return           The string as pure text, `NULL` on error
 */
static char32_t* parse_keys(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff)
{
#define GROW_BUF								\
  if (buf_ptr == buf_size)							\
    fail_if (xxrealloc(old_buf, buf, buf_size ? (buf_size <<= 1) : 16, char))
#define COPY							\
  n = string_length(subrc);					\
  if (rc_ptr + n > rc_size)					\
    fail_if (xxrealloc(old_rc, rc, rc_ptr + n, char32_t));	\
  memcpy(rc + rc_ptr, subrc, n * sizeof(char32_t));		\
  free(subrc), subrc = NULL
#define STORE							\
  GROW_BUF;							\
  buf[buf_ptr] = '\0', buf_ptr = 0;				\
  fail_if ((subrc = string_decode(buf), subrc == NULL));	\
  COPY
  
  mds_kbdc_tree_t* old_last_value_statement = last_value_statement;
  const char* restrict raw_ = raw++;
  char32_t* restrict subrc = NULL;
  char32_t* restrict rc = NULL;
  char32_t* restrict old_rc = NULL;
  char* restrict buf = NULL;
  char* restrict old_buf = NULL;
  size_t rc_ptr = 0, rc_size = 0, n;
  size_t buf_ptr = 0, buf_size = 0, i;
  int escape = 0;
  char c;
  int saved_errno;
  
  /* Parse the string. */
  while (c = *raw++, *raw)
    if (escape && strchr("()[]{}<>\"\\,", c))
      {
	/* Buffer UTF-8 text for convertion to UTF-32. */
	GROW_BUF;
	buf[buf_ptr++] = c;
	escape = 0;
      }
    else if (escape)
      {
	/* Parse escape. */
	raw -= 2, subrc = parse_escape(tree, raw, lineoff + (size_t)(raw - raw_), &escape, &raw);
	fail_if (subrc == NULL);
	COPY;
      }
    else if (c == '\\')
      {
	/* Convert the buffered UTF-8 text to UTF-32, and start an escape. */
	STORE;
	escape = 1;
      }
    else if (c == ',')
      {
	/* Include commas as (1 << 31) ^ 1 (above 2³¹, yet guaranteed not to be -1). */
	for (i = 0; i < 7; i++)
	  GROW_BUF;
	buf[buf_ptr++] = (char)0xFE;
	for (i = 0; i < 5; i++)
	  buf[buf_ptr++] = 0x00;
	buf[buf_ptr++] = (char)(((1ULL << 31) ^ 1ULL) & 255);
      }
    else
      {
	/* Buffer UTF-8 text for convertion to UTF-32. */
	GROW_BUF;
	buf[buf_ptr++] = c;
      }
  
  /* Check that no escape is incomplete. */
  if (escape && (tree->processed != PROCESS_LEVEL))
    {
      NEW_ERROR(tree, ERROR, "incomplete escape");
      error->start = lineoff + (size_t)(strrchr(raw_, '\\') - raw);
      error->end = lineoff + strlen(raw_);
      tree->processed = PROCESS_LEVEL;
    }
  
  /* Check that key-combination is complete. */
  if ((c != '>') && (tree->processed != PROCESS_LEVEL))
    {
      NEW_ERROR(tree, ERROR, "key-combination is not closed");
      error->start = lineoff;
      error->end = lineoff + strlen(raw_);
      tree->processed = PROCESS_LEVEL;
    }
  
  /* Shrink or grow to string to its minimal size, and -1-terminate it. */
  fail_if (xxrealloc(old_rc, rc, rc_ptr + 1, char32_t));
  rc[rc_ptr] = -1;
  
  free(buf);
  return last_value_statement = old_last_value_statement, rc;
 pfail:
  saved_errno = errno;
  free(subrc);
  free(old_rc);
  free(old_buf);
  free(rc);
  free(buf);
  errno = saved_errno;
  return last_value_statement = old_last_value_statement, NULL;
#undef STORE
#undef COPY
#undef GROW_BUF
}


/**
 * Parse a variable string
 * 
 * @param   tree     The statement where the variable is selected
 * @param   raw      The variable string
 * @param   lineoff  The offset on the line where the variable string begins
 * @return           The index of the variable, zero on error
 */
static size_t parse_variable(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff)
{
  int bad = 0;
  size_t var;
  const char* restrict raw_ = raw;
  
  /* The variable must begin with \. */
  if (*raw++ != '\\')  bad = 1;
  /* Zero is not a valid varible, nor may there be leading zeroes.  */
  if (*raw++ == '0')  bad = 1;
  for (; *raw; raw++)
    /* Check that the variable consists only of digits. */
    if (('0' <= *raw) && (*raw <= '9'));
    /* However, it may end with a dot. */
    else if ((raw[0] == '.') && (raw[1] == '\0'));
    else
      bad = 1;
  
  /* Report an error but return a variable index if the variable-string is invalid. */
  if (bad)
    {
      NEW_ERROR(tree, ERROR, "not a variable");
      error->start = lineoff;
      error->end = lineoff + strlen(raw_);
      tree->processed = PROCESS_LEVEL;
      return 1;
    }
  
  /* Parse the variable string and check that it did not overflow. */
  var = (size_t)atoll(raw_ + 1);
  if (strlen(raw_ + 1) != (size_t)snprintf(NULL, 0, "%zu", var))
    return errno = ERANGE, (size_t)0;
  return var;
 pfail:
  return 0;
}


/**
 * Parse an argument in a function call
 * 
 * @param   tree     The statement where the function call appear
 * @param   raw      The beginning of the argument for the function call
 * @param   lineoff  The offset for `raw` on line in which it appears
 * @param   end      Output parameter for the end of the argument
 * @param   value    Output parameter for the value to which the argument evaulates
 * @return           Zero on success, -1 on error
 */
static int parse_function_argument(mds_kbdc_tree_t* restrict tree, const char* restrict raw, size_t lineoff,
				   const char* restrict* restrict end, char32_t** restrict value)
{
  size_t size = strlen(raw), ptr = 0, call_end = 0;
  int escape = 0, quote = 0;
  char* raw_argument = NULL;
  int saved_errno;
  
  /* Find the span of the argument. */
  while (ptr < size)
    {
      char c = raw[ptr++];
      
      /* Escapes may be longer than one character,
         but only the first can affect the parsing. */
      if (escape)                escape = 0;
      /* Nested function and nested quotes can appear. */
      else if (ptr <= call_end)  ;
      /* Quotes end with the same symbols as they start with,
         and quotes automatically escape brackets. */
      /* \ can either start a functon call or an escape. */
      else if (c == '\\')
	{
	  /* It may not be an escape, but registering it
	     as an escape cannot harm us since we only
	     skip the first character, and a function call
	     cannot be that short. */
	  escape = 1;
	  /* Nested quotes can appear at function calls. */
	  call_end = get_end_of_call(raw, ptr, size);
	}
      /* " is the quote symbol. */
      else if (quote)            quote = (c != '"');
      else if (c == '"')         quote = 1;
      /* End of argument? */
      else if (strchr(" )", c))
	{
	  ptr--;
	  break;
	}
    }
  *end = raw + ptr;
  
  /* Copy the argument so that we have a NUL-terminates string. */
  fail_if (xmalloc(raw_argument, ptr + 1, char));
  memcpy(raw_argument, raw, ptr * sizeof(char));
  raw_argument[ptr] = '\0';
  
  /* Evaluate argument. */
  *value = parse_string(tree, raw_argument, lineoff);
  fail_if (*value == NULL);
  
  free(raw_argument);
  return 0;
  FAIL_BEGIN;
  free(raw_argument);
  FAIL_END;
}


/**
 * Store a macro
 * 
 * @param   macro                The macro
 * @param   macro_include_stack  The include-stack for the macro
 * @return                       Zero on success, -1 on error
 */
static int set_macro(mds_kbdc_tree_macro_t* restrict macro,
		     mds_kbdc_include_stack_t* macro_include_stack)
{
  return callables_set(macro->name, 0, (mds_kbdc_tree_t*)macro, macro_include_stack);
}


/**
 * Get a stored macro
 * 
 * @param  name                 The name of the macro, with suffix
 * @param  macro                Output parameter for the macro, `NULL` if not found
 * @param  macro_include_stack  Output parameter for the include-stack for the macro
 */
static void get_macro_lax(const char* restrict macro_name, mds_kbdc_tree_macro_t** restrict macro,
			  mds_kbdc_include_stack_t** restrict macro_include_stack)
{
  callables_get(macro_name, 0, (mds_kbdc_tree_t**)macro, macro_include_stack);
}


/**
 * Get a stored macro
 * 
 * The function is similar to `get_macro_lax`, however, this fucntion
 * will report an error if the macro has not yet been defined, and it
 * will pretend that it has not yet been defined if the macro contained
 * an error in an earlier called to it
 * 
 * @param   macro_call           The macro-call
 * @param   macro                Output parameter for the macro, `NULL` if not found or has an error
 * @param   macro_include_stack  Output parameter for the include-stack for the macro
 * @return                       Zero on success, -1 on error
 */
static int get_macro(mds_kbdc_tree_macro_call_t* restrict macro_call,
		     mds_kbdc_tree_macro_t** restrict macro,
		     mds_kbdc_include_stack_t** restrict macro_include_stack)
{
  get_macro_lax(macro_call->name, macro, macro_include_stack);
  if (*macro == NULL)
    {
      NEW_ERROR(macro_call, ERROR, "macro ‘%s’ has not been defined yet", macro_call->name);
      macro_call->processed = PROCESS_LEVEL;
      return 0;
    }
  if ((*macro)->processed == PROCESS_LEVEL)
    *macro = NULL;
  return 0;
 pfail:
  return -1;
}


/**
 * Store a function
 * 
 * @param   function                The function
 * @param   function_include_stack  The include-stack for the function
 * @return                          Zero on success, -1 on error
 */
static int set_function(mds_kbdc_tree_function_t* restrict function,
			mds_kbdc_include_stack_t* function_include_stack)
{
  char* suffixless = function->name;
  char* suffix_start = strchr(suffixless, '/');
  size_t arg_count = (size_t)atoll(suffix_start + 1);
  int r;
  
  *suffix_start = '\0';
  r = callables_set(suffixless, arg_count, (mds_kbdc_tree_t*)function, function_include_stack);
  return *suffix_start = '/', r;
}


/**
 * Get a stored function
 * 
 * @param  name                    The name of the function, suffixless
 * @param  arg_count               The number of arguments the function takes
 * @param  function                Output parameter for the function, `NULL` if not found
 * @param  function_include_stack  Output parameter for the include-stack for the function
 */
static void get_function_lax(const char* restrict function_name, size_t arg_count,
			     mds_kbdc_tree_function_t** restrict function,
			     mds_kbdc_include_stack_t** restrict function_include_stack)
{
  callables_get(function_name, arg_count, (mds_kbdc_tree_t**)function, function_include_stack);
}


/**
 * Store a value for being returned by the current function
 * 
 * @param   value  The value the function should return
 * @return         Zero on success, 1 if no function is currently being called
 */
static int set_return_value(char32_t* restrict value)
{
  if (current_return_value == NULL)
    return free(value), 1;
  free(*current_return_value);
  *current_return_value = value;
  return 0;
}


static int add_mapping(mds_kbdc_tree_map_t* restrict mapping, mds_kbdc_include_stack_t* restrict include_stack)
{
  mds_kbdc_tree_free((mds_kbdc_tree_t*)mapping);
  mds_kbdc_include_stack_free(include_stack);
  return 0; /* TODO */
}



/*** Tree-walking. ***/


/**
 * Compile an include-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_include(mds_kbdc_tree_include_t* restrict tree)
{
  void* data;
  int r;
  if (mds_kbdc_include_stack_push(tree, &data))
    return -1;
  r = compile_subtree(tree->inner);
  mds_kbdc_include_stack_pop(data);
  
  /* For simplicity we set `last_value_statement` on includes,
   * so we are sure `last_value_statement` has the same
   * include-stack as its overriding statement. */
  last_value_statement = NULL;
  
  return r;
}


/**
 * Compile a language-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_language(mds_kbdc_tree_information_language_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict data = NULL;
  char** old = NULL;
  int saved_errno;
  
  /* Make sure the language-list fits another entry. */
  if (result->languages_ptr == result->languages_size)
    {
      result->languages_size = result->languages_size ? (result->languages_size << 1) : 1;
      fail_if (xxrealloc(old, result->languages, result->languages_size, char*));
    }
  
  /* Locate the first character in the language-string. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  /* Evaluate function calls, variable dereferences and escapes in the language-string. */
  fail_if ((data = parse_string((mds_kbdc_tree_t*)tree, tree->data, lineoff), data == NULL));
  if (tree->processed == PROCESS_LEVEL)
    return free(data), 0;
  /* We want the string in UTF-8, not UTF-16. */
  fail_if ((code = string_encode(data), code == NULL));
  free(data);
  
  /* Add the language to the language-list. */
  result->languages[result->languages_ptr++] = code;
  
  return 0;
  FAIL_BEGIN;
  free(old);
  free(data);
  FAIL_END;
}


/**
 * Compile a country-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_country(mds_kbdc_tree_information_country_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict data = NULL;
  char** old = NULL;
  int saved_errno;
  
  /* Make sure the country-list fits another entry. */
  if (result->countries_ptr == result->countries_size)
    {
      result->countries_size = result->countries_size ? (result->countries_size << 1) : 1;
      fail_if (xxrealloc(old, result->countries, result->countries_size, char*));
    }
  
  /* Locate the first character in the country-string. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  /* Evaluate function calls, variable dereferences and escapes in the country-string. */
  fail_if ((data = parse_string((mds_kbdc_tree_t*)tree, tree->data, lineoff), data == NULL));
  if (tree->processed == PROCESS_LEVEL)
    return free(data), 0;
  /* We want the string in UTF-8, not UTF-16. */
  fail_if ((code = string_encode(data), code == NULL));
  free(data);
  
  /* Add the country to the country-list. */
  result->countries[result->countries_ptr++] = code;
  
  return 0;
  FAIL_BEGIN;
  free(old);
  free(data);
  FAIL_END;
}


/**
 * Compile a variant-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_variant(mds_kbdc_tree_information_variant_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict data = NULL;
  int saved_errno;
  
  /* Make sure the variant has not already been set. */
  if (result->variant)
    {
      if (multiple_variants == 0)
	NEW_ERROR(tree, ERROR, "only one ‘variant’ is allowed");
      multiple_variants = 1;
      return 0;
    }
  
  /* Locate the first character in the variant-string. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  /* Evaluate function calls, variable dereferences and escapes in the variant-string. */
  fail_if ((data = parse_string((mds_kbdc_tree_t*)tree, tree->data, lineoff), data == NULL));
  if (tree->processed == PROCESS_LEVEL)
    return free(data), 0;
  /* We want the string in UTF-8, not UTF-16. */
  fail_if ((code = string_encode(data), code == NULL));
  free(data);
  
  /* Store the variant. */
  result->variant = code;
  
  return 0;
  FAIL_BEGIN;
  free(data);
  FAIL_END;
}


/**
 * Compile a have-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_have(mds_kbdc_tree_assumption_have_t* restrict tree)
{
  mds_kbdc_tree_t* node = tree->data;
  char32_t* data = NULL;
  char32_t** old = NULL;
  size_t new_size = 0;
  int saved_errno;
  
  /* Make sure we can fit all assumption in the assumption list (part 1/2). */
  new_size = (node->type == C(STRING)) ? result->assumed_strings_size : result->assumed_keys_size;
  new_size = new_size ? (new_size << 1) : 1;
  
  if (node->type == C(STRING))
    {
      /* Evaluate function calls, variable dereferences and escapes in the string. */
      fail_if ((data = parse_string(node, node->string.string, node->loc_start), data == NULL));
      if (node->processed == PROCESS_LEVEL)
	return free(data), 0;
      /* Make sure we can fit all strings in the assumption list (part 2/2). */
      if (result->assumed_strings_ptr == result->assumed_strings_size)
	fail_if (xxrealloc(old, result->assumed_strings, new_size, char*));
      result->assumed_strings_size = new_size;
      /* Add the assumption to the list. */
      result->assumed_strings[result->assumed_strings_ptr++] = data;
    }
  else
    {
      /* Evaluate function calls, variable dereferences and escapes in the key-combination. */
      fail_if ((data = parse_keys(node, node->keys.keys, node->loc_start), data == NULL));
      if (node->processed == PROCESS_LEVEL)
	return free(data), 0;
      /* Make sure we can fit all key-combinations in the assumption list (part 2/2). */
      if (result->assumed_keys_ptr == result->assumed_keys_size)
	fail_if (xxrealloc(old, result->assumed_keys, new_size, char*));
      result->assumed_keys_size = new_size;
      /* Add the assumption to the list. */
      result->assumed_keys[result->assumed_keys_ptr++] = data;
    }
  
  return 0;
  FAIL_BEGIN;
  free(old);
  free(data);
  FAIL_END;
}


/**
 * Compile a have_chars-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_have_chars(mds_kbdc_tree_assumption_have_chars_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict data = NULL;
  char32_t** old = NULL;
  char32_t* restrict character;
  size_t n;
  int saved_errno;
  
  /* Locate the first character in the list. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  /* Evaluate function calls, variable dereferences
     and escapes in the charcter list. */
  fail_if ((data = parse_string((mds_kbdc_tree_t*)tree, tree->chars, lineoff), data == NULL));
  if (tree->processed == PROCESS_LEVEL)
    return free(data), 0;
  
  /* Make sure we can fit all characters in the assumption list. */
  for (n = 0; data[n] >= 0; n++);
  if (result->assumed_strings_ptr + n > result->assumed_strings_size)
    {
      result->assumed_strings_size += n;
      fail_if (xxrealloc(old, result->assumed_strings, result->assumed_strings_size, char*));
    }
  
  /* Add all characters to the assumption list. */
  while (n--)
    {
      fail_if (xmalloc(character, 2, char32_t));
      character[0] = data[n];
      character[1] = -1;
      result->assumed_strings[result->assumed_strings_ptr++] = character;
    }
  
  free(data);
  return 0;
  FAIL_BEGIN;
  free(data);
  free(old);
  FAIL_END;
}


/**
 * Compile a have_range-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_have_range(mds_kbdc_tree_assumption_have_range_t* restrict tree)
{
  size_t lineoff_first;
  size_t lineoff_last;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict first = NULL;
  char32_t* restrict last = NULL;
  char32_t** old = NULL;
  char32_t* restrict character;
  size_t n;
  int saved_errno;
  
  
  /* Locate the first characters of both bound strings. */
  for (lineoff_first = tree->loc_end; code[lineoff_first] == ' '; lineoff_first++);
  for (lineoff_last = lineoff_first + strlen(tree->first); code[lineoff_last] == ' '; lineoff_last++);
  
  /* Duplicate bounds and evaluate function calls,
     variable dereferences and escapes in the bounds. */
  fail_if ((first = parse_string((mds_kbdc_tree_t*)tree, tree->first, lineoff_first), first == NULL));
  fail_if ((last = parse_string((mds_kbdc_tree_t*)tree, tree->last, lineoff_last), last == NULL));
  
  /* Did one of the bound not evaluate, then stop. */
  if (tree->processed == PROCESS_LEVEL)
    goto done;
  
  
  /* Check that the primary bound is single-character. */
  if ((first[0] < 0) || (first[1] >= 0))
    {
      NEW_ERROR(tree, ERROR, "iteration boundary must be a single character string");
      error->start = lineoff_first, lineoff_first = 0;
      error->end = error->start + strlen(tree->first);
    }
  /* Check that the secondary bound is single-character. */
  if ((last[0] < 0) || (last[1] >= 0))
    {
      NEW_ERROR(tree, ERROR, "iteration boundary must be a single character string");
      error->start = lineoff_last, lineoff_last = 0;
      error->end = error->start + strlen(tree->last);
    }
  
  /* Was one of the bounds not single-character, then stop. */
  if ((lineoff_first == 0) || (lineoff_last == 0))
    goto done;
  
  
  /* If the range is descending, swap the bounds so it is ascending.
     (This cannot be done in for-loops as that may cause side-effects
     to be created in the wrong order.) */
  if (*first > *last)
    *first ^= *last, *last ^= *first, *first ^= *last;
  
  /* Make sure we can fit all characters in the assumption list. */
  n = (size_t)(*last - *first) + 1;
  if (result->assumed_strings_ptr + n > result->assumed_strings_size)
    {
      result->assumed_strings_size += n;
      fail_if (xxrealloc(old, result->assumed_strings, result->assumed_strings_size, char*));
    }
  
  /* Add all characters to the assumption list. */
  while (*first != *last)
    {
      fail_if (xmalloc(character, 2, char32_t));
      character[0] = (*first)++;
      character[1] = -1;
      result->assumed_strings[result->assumed_strings_ptr++] = character;
    }
  
 done:
  free(first);
  free(last);
  return 0;
  FAIL_BEGIN;
  free(first);
  free(last);
  free(old);
  FAIL_END;
}


/**
 * Check that all called macros are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined macro is used
 */
static int check_marco_calls(mds_kbdc_tree_t* restrict tree)
{
#define t(...)   if (rc |= r = (__VA_ARGS__), r < 0)  return r
  mds_kbdc_tree_macro_t* _macro;
  mds_kbdc_include_stack_t* _macro_include_stack;
  void* data;
  int r, rc = 0;
 again:
  if (tree == NULL)
    return rc;
  
  switch (tree->type)
    {
    case C(INCLUDE):
      t (mds_kbdc_include_stack_push(&(tree->include), &data));
      t (r = check_marco_calls(tree->include.inner), mds_kbdc_include_stack_pop(data), r);
      break;
      
    case C(FOR):
      t (check_marco_calls(tree->for_.inner));
      break;
      
    case C(IF):
      t (check_marco_calls(tree->if_.inner));
      t (check_marco_calls(tree->if_.otherwise));
      break;
      
    case C(MACRO_CALL):
      t (get_macro(&(tree->macro_call), &_macro, &_macro_include_stack));
      break;
      
    default:
      break;
    }
  
  tree = tree->next;
  goto again;
  (void) _macro;
  (void) _macro_include_stack;
#undef t
}


/**
 * Check that all called functions in a for-statement are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls_in_for(const mds_kbdc_tree_for_t* restrict tree)
{
#define t(...)  if (rc |= r = check_function_calls_in_literal(__VA_ARGS__), r < 0)  return r
  size_t lineoff_first;
  size_t lineoff_last;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  int r, rc = 0;
  
  for (lineoff_first = tree->loc_end; code[lineoff_first] == ' '; lineoff_first++);
  for (lineoff_last = lineoff_first + strlen(tree->first); code[lineoff_last] == ' '; lineoff_last++);
  
  t ((const mds_kbdc_tree_t*)tree, tree->first, lineoff_first);
  t ((const mds_kbdc_tree_t*)tree, tree->last, lineoff_last);
  
  return rc;
#undef t
}


/**
 * Check that all called functions in an if-statement are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls_in_if(const mds_kbdc_tree_if_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  return check_function_calls_in_literal((const mds_kbdc_tree_t*)tree, tree->condition, lineoff);
}


/**
 * Check that all called functions in a key-combination are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls_in_keys(const mds_kbdc_tree_keys_t* restrict tree)
{
  return check_function_calls_in_literal((const mds_kbdc_tree_t*)tree, tree->keys, tree->loc_end);
}


/**
 * Check that all called functions in a string are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls_in_string(const mds_kbdc_tree_string_t* restrict tree)
{
  return check_function_calls_in_literal((const mds_kbdc_tree_t*)tree, tree->string, tree->loc_end);
}


/**
 * Check that all called functions are already defined
 * 
 * @param   tree  The tree to evaluate
 * @return        Zero on success, -1 on error, 1 if an undefined function is used
 */
static int check_function_calls(const mds_kbdc_tree_t* restrict tree)
{
#define t(...)   if (rc |= r = (__VA_ARGS__), r < 0)  return r
  void* data;
  int r, rc = 0;
 again:
  if (tree == NULL)
    return rc;
  
  switch (tree->type)
    {
    case C(INCLUDE):
      t (mds_kbdc_include_stack_push(&(tree->include), &data));
      t (r = check_function_calls(tree->include.inner), mds_kbdc_include_stack_pop(data), r);
      break;
      
    case C(FOR):
      t (check_function_calls_in_for(&(tree->for_)));
      t (check_function_calls(tree->for_.inner));
      break;
      
    case C(IF):
      t (check_function_calls_in_if(&(tree->if_)));
      t (check_function_calls(tree->if_.inner));
      t (check_function_calls(tree->if_.otherwise));
      break;
      
    case C(LET):     t (check_function_calls(tree->let.value));            break;
    case C(ARRAY):   t (check_function_calls(tree->array.elements));       break;
    case C(KEYS):    t (check_function_calls_in_keys(&(tree->keys)));      break;
    case C(STRING):  t (check_function_calls_in_string(&(tree->string)));  break;
    case C(MAP):     t (check_function_calls(tree->map.sequence));         break;
    default:
      break;
    }
  
  tree = tree->next;
  goto again;
#undef t
}


/**
 * Check that a callable's name-suffix is correct
 * 
 * @param   tree  The tree to inspect
 * @return        Zero on sucess, -1 on error, 1 if the name-suffix in invalid
 */
static int check_name_suffix(struct mds_kbdc_tree_callable* restrict tree)
{
  const char* restrict name = strchr(tree->name, '/');
  const char* restrict code = result->source_code->real_lines[tree->loc_line];
  
  /* A "/" must exist in the name to tell us how many parameters there are. */
  if (name == NULL)
    {
      NEW_ERROR(tree, ERROR, "name-suffix is missing");
      goto name_error;
    }
  /* Do not let the suffix by just "/". */
  if (*++name == '\0')
    {
      NEW_ERROR(tree, ERROR, "empty name-suffix");
      goto name_error;
    }
  
  /* We are all good if the suffix is simply "/0" */
  if (!strcmp(name, "0"))
    return 0;
  
  /* The suffix may not have leading zeroes. */
  if (*name == '\0')
    {
      NEW_ERROR(tree, ERROR, "leading zero in name-suffix");
      goto name_error;
    }
  /* The suffix must be a decimal, non-negative number. */
  for (; *name; name++)
    if ((*name < '0') || ('0' < *name))
      {
	NEW_ERROR(tree, ERROR, "name-suffix may only contain digits");
	goto name_error;
      }
  
  return 0;
 pfail:
  return -1;
 name_error:
  error->start = tree->loc_end;
  while (code[error->start] == ' ')
    error->start++;
  error->end = error->start + strlen(tree->name);
  tree->processed = PROCESS_LEVEL;
  return 1;
}


/**
 * Compile a function
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_function(mds_kbdc_tree_function_t* restrict tree)
{
#define t(expr)  fail_if ((r = (expr), r < 0));  if (r)  tree->processed = PROCESS_LEVEL
  mds_kbdc_tree_function_t* function;
  mds_kbdc_include_stack_t* function_include_stack;
  mds_kbdc_include_stack_t* our_include_stack = NULL;
  char* suffixless;
  char* suffix_start = NULL;
  size_t arg_count;
  int r, saved_errno;
  
  /* Check that the suffix if properly formatted. */
  t (check_name_suffix((struct mds_kbdc_tree_callable*)tree));
  
  /* Get the function's name without suffix, and parse the suffix. */
  suffixless = tree->name;
  suffix_start = strchr(suffixless, '/');
  *suffix_start++ = '\0';
  arg_count = (size_t)atoll(suffix_start--);
  
  /* Check that the function is not already defined as a builtin function. */
  if (builtin_function_defined(suffixless, arg_count))
    {
      NEW_ERROR(tree, ERROR, "function ‘%s’ is already defined as a builtin function", tree->name);
      *suffix_start = '/';
      return 0;
    }
  /* Check that the function is not already defined,
     the include-stack is used in the error-clause as
     well as later when we list the function as defined. */
  get_function_lax(suffixless, arg_count, &function, &function_include_stack);
  fail_if ((our_include_stack = mds_kbdc_include_stack_save(), our_include_stack == NULL));
  if (function)
    {
      *suffix_start = '/';
      NEW_ERROR(tree, ERROR, "function ‘%s’ is already defined", tree->name);
      fail_if (mds_kbdc_include_stack_restore(function_include_stack));
      NEW_ERROR(function, NOTE, "previously defined here");
      fail_if (mds_kbdc_include_stack_restore(our_include_stack));
      mds_kbdc_include_stack_free(our_include_stack);
      return 0;
    }
  
  /* Check the the function does not call macros or functions
   * before they are defined, otherwise they may get defined
   * between the definition of the function and calls to it. */
  t (check_marco_calls(tree->inner));
  t (check_function_calls(tree->inner));
  
  /* List the function as defined. */
  *suffix_start = '/', suffix_start = NULL;
  t (set_function(tree, our_include_stack));
  
  return 0;
  FAIL_BEGIN;
  if (suffix_start)
    *suffix_start = '/';
  mds_kbdc_include_stack_free(our_include_stack);
  FAIL_END;
#undef t
}


/**
 * Compile a macro
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_macro(mds_kbdc_tree_macro_t* restrict tree)
{
#define t(expr)  fail_if ((r = (expr), r < 0));  if (r)  tree->processed = PROCESS_LEVEL
  mds_kbdc_tree_macro_t* macro;
  mds_kbdc_include_stack_t* macro_include_stack;
  mds_kbdc_include_stack_t* our_include_stack = NULL;
  int r, saved_errno;
  
  /* Check that the suffix if properly formatted. */
  t (check_name_suffix((struct mds_kbdc_tree_callable*)tree));
  
  /* Check that the macro is not already defined,
     the include-stack is used in the error-clause as
     well as later when we list the macro as defined. */
  fail_if ((our_include_stack = mds_kbdc_include_stack_save(), our_include_stack == NULL));
  get_macro_lax(tree->name, &macro, &macro_include_stack);
  if (macro)
    {
      NEW_ERROR(tree, ERROR, "macro ‘%s’ is already defined", tree->name);
      fail_if (mds_kbdc_include_stack_restore(macro_include_stack));
      NEW_ERROR(macro, NOTE, "previously defined here");
      fail_if (mds_kbdc_include_stack_restore(our_include_stack));
      mds_kbdc_include_stack_free(our_include_stack);
      return 0;
    }
  
  /* Check the the macro does not call macros or functions
   * before they are defined, otherwise they may get defined
   * between the definition of the macro and calls to it. */
  t (check_marco_calls(tree->inner));
  t (check_function_calls(tree->inner));
  
  /* List the macro as defined. */
  t (set_macro(tree, our_include_stack));
  
  return 0;
  FAIL_BEGIN;
  mds_kbdc_include_stack_free(our_include_stack);
  FAIL_END;
#undef t
}


/**
 * Compile a for-loop
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_for(mds_kbdc_tree_for_t* restrict tree)
{
  size_t lineoff_first;
  size_t lineoff_last;
  size_t lineoff_var;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict first = NULL;
  char32_t* restrict last = NULL;
  char32_t diff;
  char32_t character[2];
  size_t variable;
  int saved_errno;
  
  
  last_value_statement = NULL;
  
  
  /* Locate the first character of the primary bound's string. */
  for (lineoff_first = tree->loc_end; code[lineoff_first] == ' '; lineoff_first++);
  /* Locate the first character of the secondary bound's string. */
  for (lineoff_last = lineoff_first + strlen(tree->first); code[lineoff_last] == ' '; lineoff_last++);
  for (lineoff_last += strlen("to"); code[lineoff_last] == ' '; lineoff_last++);
  /* Locate the first character of the select variable. */
  for (lineoff_var = lineoff_last + strlen(tree->variable); code[lineoff_var] == ' '; lineoff_var++);
  for (lineoff_var += strlen("as"); code[lineoff_var] == ' '; lineoff_var++);
  
  /* Duplicate bounds and evaluate function calls,
     variable dereferences and escapes in the bounds. */
  fail_if ((first = parse_string((mds_kbdc_tree_t*)tree, tree->first, lineoff_first), first == NULL));
  fail_if ((last = parse_string((mds_kbdc_tree_t*)tree, tree->last, lineoff_last), last == NULL));
  /* Get the index of the selected variable. */
  fail_if ((variable = parse_variable((mds_kbdc_tree_t*)tree, tree->variable, lineoff_var), variable == 0));
  
  /* Did one of the bound not evaluate, then stop. */
  if (tree->processed == PROCESS_LEVEL)
    goto done;
  
  
  /* Check that the primary bound is single-character. */
  if ((first[0] < 0) || (first[1] >= 0))
    {
      NEW_ERROR(tree, ERROR, "iteration boundary must be a single character string");
      error->start = lineoff_first, lineoff_first = 0;
      error->end = error->start + strlen(tree->first);
    }
  /* Check that the secondary bound is single-character. */
  if ((last[0] < 0) || (last[1] >= 0))
    {
      NEW_ERROR(tree, ERROR, "iteration boundary must be a single character string");
      error->start = lineoff_last, lineoff_last = 0;
      error->end = error->start + strlen(tree->last);
    }
  
  /* Was one of the bounds not single-character, then stop. */
  if ((lineoff_first == 0) || (lineoff_last == 0))
    goto done;
  
  
  /* Iterate over the loop for as long as a `return` or `break` has not
     been encountered (without being caught elsewhere). */
  character[1] = -1;
  for (diff = (*first > *last) ? -1 : +1; (*first != *last) && (break_level < 2); *first += diff)
    {
      break_level = 0;
      character[0] = *first;
      fail_if (let(variable, character, NULL, (mds_kbdc_tree_t*)tree, lineoff_var, 1));
      fail_if (compile_subtree(tree->inner));
    }
  
  /* Catch `break` and `continue`, they may not propagate further. */
  if (break_level < 3)
    break_level = 0;
  
  
 done:
  last_value_statement = NULL;
  free(first);
  free(last);
  return 0;
  FAIL_BEGIN;
  free(first);
  free(last);
  FAIL_END;
}


/**
 * Compile an if-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_if(mds_kbdc_tree_if_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  char32_t* restrict data = NULL;
  int ok, saved_errno;
  size_t i;
  
  last_value_statement = NULL;
  
  /* Locate the first character in the condition. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  /* Evaluate function calls, variable dereferences and escapes in the condition. */
  fail_if ((data = parse_string((mds_kbdc_tree_t*)tree, tree->condition, lineoff), data == NULL));
  if (tree->processed == PROCESS_LEVEL)
    return free(data), 0;
  
  /* Evaluate whether the evaluted value is true. */
  for (ok = 1, i = 0; data[i] >= 0; i++)
    ok &= !!(data[i]);
  free(data);
  
  /* Compile the appropriate clause. */
  ok = compile_subtree(ok ? tree->inner : tree->otherwise);
  last_value_statement = NULL;
  return ok;
  FAIL_BEGIN;
  free(data);
  FAIL_END;
}


/**
 * Compile a let-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_let(mds_kbdc_tree_let_t* restrict tree)
{
  size_t lineoff;
  char* restrict code = result->source_code->real_lines[tree->loc_line];
  mds_kbdc_tree_t* value = NULL;
  size_t variable;
  int saved_errno;
  
  /* Get the index of the selected variable. */
  for (lineoff = tree->loc_end; code[lineoff] == ' '; lineoff++);
  fail_if ((variable = parse_variable((mds_kbdc_tree_t*)tree, tree->variable, lineoff), variable == 0));
  if (tree->processed == PROCESS_LEVEL)
    return 0;
  
  /* Duplicate arguments and evaluate function calls,
     variable dereferences and escapes in the value. */
  fail_if ((value = mds_kbdc_tree_dup(tree->value), value == NULL));
  fail_if (compile_subtree(value));
  if ((tree->processed = value->processed) == PROCESS_LEVEL)
    return 0;
  
  /* Set the value of the variable. */
  fail_if (let(variable, NULL, value, NULL, 0, 0));
  
  mds_kbdc_tree_free(value);
  return 0;
  FAIL_BEGIN;
  free(value);
  FAIL_END;
}


/*
 * `compile_keys`, `compile_string`, `compile_array` and `evaluate_element`
 * are do only compilation subprocedures that may alter the compiled nodes.
 * This is because (1) `compile_let`, `compile_map` and `compile_macro_call`
 * needs the compiled values, and (2) only duplicates of nodes of types
 * `C(KEYS)`, `C(STRING)` and `C(ARRAY)` are compiled, as they can only be
 * found with `C(LET)`-, `C(MAP)`- and `C(MACRO_CALL)`-nodes.
 */


/**
 * Evaluate an element or argument in a mapping-, value-, let-statement or macro call
 * 
 * @param   node  The element to evaluate
 * @return        Zero on success, -1 on error, 1 if the element is invalid
 */
static int evaluate_element(mds_kbdc_tree_t* restrict node)
{
  char32_t* restrict data = NULL;
  int bad = 0;
  
  for (; node; node = node->next)
    {
      if (node->type == C(STRING))
	fail_if ((data = parse_string(node, node->string.string, node->loc_start), data == NULL));
      if (node->type == C(KEYS))
	fail_if ((data = parse_keys(node, node->keys.keys, node->loc_start), data == NULL));
      free(node->string.string);
      node->type = (node->type == C(STRING)) ? C(COMPILED_STRING) : C(COMPILED_KEYS);
      node->compiled_string.string = data;
      bad |= (node->processed == PROCESS_LEVEL);
    }
  
  return bad;
 pfail:
  return -1;
}


/**
 * Compile a key-combination
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_keys(mds_kbdc_tree_keys_t* restrict tree)
{
  return evaluate_element((mds_kbdc_tree_t*)tree) < 0 ? -1 : 0;
}


/**
 * Compile a string
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_string(mds_kbdc_tree_string_t* restrict tree)
{
  return evaluate_element((mds_kbdc_tree_t*)tree) < 0 ? -1 : 0;
}


/**
 * Compile an array
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_array(mds_kbdc_tree_array_t* restrict tree)
{
  int r = evaluate_element(tree->elements);
  if (r < 0)
    return -1;
  if (r)
    tree->processed = PROCESS_LEVEL;
  return 0;
}


/**
 * Check that a chain of strings and key-combinations
 * does not contain NULL characters
 * 
 * @param   tree  The tree to check
 * @return        Zero on success, -1 on error, 1 if any of
 *                the elements contain a NULL character
 */
static int check_nonnul(mds_kbdc_tree_t* restrict tree)
{
  const char32_t* restrict string;
  int rc = 0;
 again:
  if (tree == NULL)
    return rc;
  
  for (string = tree->compiled_string.string; *string != -1; string++)
    if (*string == 0)
      {
	NEW_ERROR(tree, ERROR, "NULL characters are not allowed in mappings");
	tree->processed = PROCESS_LEVEL;
	rc = 1;
	break;
      }
  
  tree = tree->next;
  goto again;
 pfail:
   return -1;
}


/**
 * Compile a mapping- or value-statement
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_map(mds_kbdc_tree_map_t* restrict tree)
{
  int bad = 0, old_have_side_effect = have_side_effect;
  mds_kbdc_include_stack_t* restrict include_stack = NULL;
  mds_kbdc_tree_t* seq = NULL;
  mds_kbdc_tree_t* res = NULL;
  mds_kbdc_tree_t* old_seq = tree->sequence;
  mds_kbdc_tree_t* old_res = tree->result;
  mds_kbdc_tree_map_t* dup_map = NULL;
  int r, saved_errno;
  mds_kbdc_tree_t* previous_last_value_statement = last_value_statement;
  
  have_side_effect = 0;
  
  /* Duplicate arguments and evaluate function calls,
     variable dereferences and escapes in the mapping
     input sequence. */
  fail_if ((seq = mds_kbdc_tree_dup(old_seq), seq = NULL));
  fail_if ((bad |= evaluate_element(seq), bad < 0));
  
  /* Duplicate arguments and evaluate function calls,
     variable dereferences and escapes in the mapping
     output sequence, unless this is a value-statement. */
  if (tree->result)
    {
      fail_if ((res = mds_kbdc_tree_dup(old_res), res = NULL));
      fail_if ((bad |= evaluate_element(res), bad < 0));
    }
  
  /* Stop if any of the mapping-arguments could not be evaluated. */
  if (bad)
    goto done;
  
  
  if (tree->result)
    {
      /* Mapping-statement. */
      
      /* Check for invalid characters in the mapping-arguments. */
      fail_if ((bad |= check_nonnul(seq), bad < 0));
      fail_if ((bad |= check_nonnul(res), bad < 0));
      if (bad)
	goto done;
      
      /* Duplicate the mapping-statement but give it the evaluated mapping-arguments. */
      tree->sequence = seq;
      tree->result = res;
      fail_if ((dup_map = &(mds_kbdc_tree_dup((mds_kbdc_tree_t*)tree)->map), dup_map = NULL));
      tree->sequence = old_seq, seq = NULL;
      tree->result = old_res, res = NULL;
      
      /* Enlist the mapping for assembling. */
      fail_if ((include_stack = mds_kbdc_include_stack_save(), include_stack == NULL));
      fail_if (add_mapping(dup_map, include_stack));
      
      goto done;
    }
  
  
  /* Value-statement */
  
  /* Save this statement so we can warn later if it is unnecessary,
   * `set_return_value` will set it to `NULL` if there are side-effects,
   * which would make this statement necessary (unless the overridding
   * statement has identical side-effect, but we will not check for that).
   * For simplicity, we do not store the include-stack, instead, we reset
   * `last_value_statement` to `NULL` when we visit an include-statement. */
  last_value_statement = (mds_kbdc_tree_t*)tree;
  
  /* Add the value statement */
  r = set_return_value(seq->compiled_string.string);
  seq->compiled_string.string = NULL;
  
  /* Check that the value-statement is inside a function call, or has
     side-effects by directly or indirectly calling ‘\set/3’ on an
     array that is not shadowed by an inner function- or macro-call. */
  if (r && !have_side_effect)
    {
      NEW_ERROR(tree, ERROR, "value-statement outside function without side-effects");
      tree->processed = PROCESS_LEVEL;
    }
  if (have_side_effect)
    last_value_statement = NULL;
  
  /* Check whether we made a previous value-statement unnecessary. */
  if (previous_last_value_statement)
    {
      /* For simplicity we set `last_value_statement` on includes,
       * so we are sure `last_value_statement` has the same include-stack. */
      
      NEW_ERROR(previous_last_value_statement, WARNING, "value-statement has no effects");
      NEW_ERROR(tree, NOTE, "overridden here");
    }
  
  
 done:
  mds_kbdc_tree_free(seq);
  mds_kbdc_tree_free(res);
  have_side_effect = old_have_side_effect;
  return 0;
  FAIL_BEGIN;
  mds_kbdc_include_stack_free(include_stack);
  mds_kbdc_tree_free((mds_kbdc_tree_t*)dup_map);
  mds_kbdc_tree_free(seq);
  mds_kbdc_tree_free(res);
  tree->sequence = old_seq;
  tree->result = old_res;
  have_side_effect = old_have_side_effect;
  FAIL_END;
}


/**
 * Compile a macro call
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_macro_call(mds_kbdc_tree_macro_call_t* restrict tree)
{
  mds_kbdc_tree_t* arg = NULL;
  mds_kbdc_tree_t* arg_;
  mds_kbdc_tree_macro_t* macro;
  mds_kbdc_include_stack_t* macro_include_stack;
  mds_kbdc_include_stack_t* our_include_stack = NULL;
  size_t variable;
  int bad, saved_errno;
  
  last_value_statement = NULL;
  
  /* Duplicate arguments and evaluate function calls,
     variable dereferences and escapes in the macro
     call arguments. */
  fail_if ((arg = mds_kbdc_tree_dup(tree->arguments), arg = NULL));
  fail_if ((bad = evaluate_element(arg), bad < 0));
  if (bad)
    return 0;
  
  /* Get the macro's subtree and include-stack, if it has
     not been defined `get_macro` will add an error message
     and return `NULL`. */
  fail_if (get_macro(tree, &macro, &macro_include_stack));
  if (macro == NULL)
    goto done;
  
  
  /* Push call stack and set parameters. */
  variables_stack_push();
  for (arg_ = arg; arg_; arg_ = arg_->next)
    fail_if (let(variable, NULL, arg_, NULL, 0, 0));
  
  /* Switch include-stack to the macro's. */
  fail_if ((our_include_stack = mds_kbdc_include_stack_save(), our_include_stack == NULL));
  fail_if (mds_kbdc_include_stack_restore(macro_include_stack));
  
  /* Call the macro. */
  fail_if (compile_subtree(macro->inner));
  
  /* Switch back the include-stack to ours. */
  fail_if (mds_kbdc_include_stack_restore(our_include_stack));
  mds_kbdc_include_stack_free(our_include_stack), our_include_stack = NULL;
  
  /* Pop call stack. */
  variables_stack_pop();
  
  
 done:
  last_value_statement = NULL;
  break_level = 0;
  mds_kbdc_tree_free(arg);
  return 0;
  FAIL_BEGIN;
  mds_kbdc_tree_free(arg);
  mds_kbdc_include_stack_free(our_include_stack);
  FAIL_END;
}


/**
 * Compile a subtree
 * 
 * @param   tree  The tree to compile
 * @return        Zero on success, -1 on error
 */
static int compile_subtree(mds_kbdc_tree_t* restrict tree)
{
#define t(expr)   if (r = (expr), r < 0)  return r
#define c(type)   t (compile_##type(&(tree->type)))
#define c_(type)  t (compile_##type(&(tree->type##_)))
  int r;
 again:
  if (tree == NULL)
    return 0;
  
  if (tree->processed == PROCESS_LEVEL)
    /* An error has occurred here before, lets skip it so
     * we do not deluge the user with errors. */
    goto next;
  
  switch (tree->type)
    {
    case C(INFORMATION):
      t (compile_subtree(tree->information.inner));
      break;
    case C(INFORMATION_LANGUAGE):   c (language);     break;
    case C(INFORMATION_COUNTRY):    c (country);      break;
    case C(INFORMATION_VARIANT):    c (variant);      break;
    case C(INCLUDE):                c (include);      break;
    case C(FUNCTION):               c (function);     break;
    case C(MACRO):                  c (macro);        break;
    case C(ASSUMPTION):
      t ((includes_ptr == 0) && compile_subtree(tree->assumption.inner));
      break;
    case C(ASSUMPTION_HAVE):        c (have);         break;
    case C(ASSUMPTION_HAVE_CHARS):  c (have_chars);   break;
    case C(ASSUMPTION_HAVE_RANGE):  c (have_range);   break;
    case C(FOR):                    c_ (for);         break;
    case C(IF):                     c_ (if);          break;
    case C(LET):                    c (let);          break;
    case C(KEYS):                   c (keys);         break;
    case C(STRING):                 c (string);       break;
    case C(ARRAY):                  c (array);        break;
    case C(MAP):                    c (map);          break;
    case C(MACRO_CALL):             c (macro_call);   break;
    case C(RETURN):                 break_level = 3;  break;
    case C(BREAK):                  break_level = 2;  break;
    case C(CONTINUE):               break_level = 1;  break;
    default:
      break;
    }
  
 next:
  if (break_level)
    /* If a `continue`, `break` or `return` has been encountered,
     * we are done here and should return to whence we came and
     * let the subcompiler of that construct deal with it. */
    return 0;
  
  tree = tree->next;
  goto again;
#undef c_
#undef c
#undef t
}


/**
 * Compile the layout code
 * 
 * @param   result_  `result` from `eliminate_dead_code`, will be updated
 * @return           -1 if an error occursed that cannot be stored in `result`, zero otherwise
 */
int compile_layout(mds_kbdc_parsed_t* restrict result_)
{
  int r, saved_errno;
  mds_kbdc_include_stack_begin(result = result_);
  r = compile_subtree(result_->tree);
  saved_errno = errno;
  mds_kbdc_include_stack_end();
  variables_terminate();
  callables_terminate();
  errno = saved_errno;
  return r;
}



#undef FAIL_END
#undef FAIL_BEGIN
#undef NEW_ERROR
#undef C
#undef PROCESS_LEVEL