cppmacro.c

/* Part of CPP library.  (Macro and #define handling.)
   Copyright (C) 1986, 1987, 1989, 1992, 1993, 1994, 1995, 1996, 1998,
   1999, 2000, 2001 Free Software Foundation, Inc.
   Written by Per Bothner, 1994.
   Based on CCCP program by Paul Rubin, June 1986
   Adapted to ANSI C, Richard Stallman, Jan 1987

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 2, 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, write to the Free Software
Foundation, 59 Temple Place - Suite 330, Boston, MA 02111-1307, USA.

 In other words, you are welcome to use, share and improve this program.
 You are forbidden to forbid anyone else to use, share and improve
 what you give them.   Help stamp out software-hoarding!  */

#include "config.h"
#include "system.h"
#include "intl.h"		/* for _("<command line>") below.  */
#include "cpplib.h"
#include "cpphash.h"

struct cpp_macro
{
  cpp_hashnode **params;	/* Parameters, if any.  */
  cpp_token *expansion;		/* First token of replacement list.   */
  unsigned int line;		/* Starting line number.  */
  unsigned int count;		/* Number of tokens in expansion.  */
  unsigned short paramc;	/* Number of parameters.  */
  unsigned int fun_like : 1;	/* If a function-like macro.  */
  unsigned int variadic : 1;	/* If a variadic macro.  */
  unsigned int disabled : 1;	/* If macro is disabled.  */
  unsigned int syshdr   : 1;	/* If macro defined in system header.  */
};

typedef struct macro_arg macro_arg;
struct macro_arg
{
  const cpp_token **first;	/* First token in unexpanded argument.  */
  const cpp_token **expanded;	/* Macro-expanded argument.   */
  const cpp_token *stringified;	/* Stringified argument.  */
  unsigned int count;		/* # of tokens in argument.  */
  unsigned int expanded_count;	/* # of tokens in expanded argument.  */
};

/* Macro expansion.  */

static int enter_macro_context PARAMS ((cpp_reader *, cpp_hashnode *));
static const cpp_token *builtin_macro PARAMS ((cpp_reader *, cpp_hashnode *));
static void push_token_context
  PARAMS ((cpp_reader *, cpp_macro *, const cpp_token *, unsigned int));
static void push_ptoken_context
  PARAMS ((cpp_reader *, cpp_macro *, _cpp_buff *,
	   const cpp_token **, unsigned int));
static _cpp_buff *collect_args PARAMS ((cpp_reader *, const cpp_hashnode *));
static cpp_context *next_context PARAMS ((cpp_reader *));
static const cpp_token *padding_token
  PARAMS ((cpp_reader *, const cpp_token *));
static void expand_arg PARAMS ((cpp_reader *, macro_arg *));
static unsigned char *quote_string PARAMS ((unsigned char *,
					    const unsigned char *,
					    unsigned int));
static const cpp_token *new_string_token PARAMS ((cpp_reader *, U_CHAR *,
						  unsigned int));
static const cpp_token *new_number_token PARAMS ((cpp_reader *, int));
static const cpp_token *stringify_arg PARAMS ((cpp_reader *, macro_arg *));
static void paste_all_tokens PARAMS ((cpp_reader *, const cpp_token *));
static bool paste_tokens PARAMS ((cpp_reader *, const cpp_token **,
				  const cpp_token *));
static int funlike_invocation_p PARAMS ((cpp_reader *, const cpp_hashnode *));
static void replace_args PARAMS ((cpp_reader *, cpp_macro *, macro_arg *));

/* #define directive parsing and handling.  */

static cpp_token *alloc_expansion_token PARAMS ((cpp_reader *, cpp_macro *));
static cpp_token *lex_expansion_token PARAMS ((cpp_reader *, cpp_macro *));
static int warn_of_redefinition PARAMS ((cpp_reader *, const cpp_hashnode *,
					 const cpp_macro *));
static int save_parameter PARAMS ((cpp_reader *, cpp_macro *, cpp_hashnode *));
static int parse_params PARAMS ((cpp_reader *, cpp_macro *));
static void check_trad_stringification PARAMS ((cpp_reader *,
						const cpp_macro *,
						const cpp_string *));

/* Allocates and returns a CPP_STRING token, containing TEXT of length
   LEN, after null-terminating it.  TEXT must be in permanent storage.  */
static const cpp_token *
new_string_token (pfile, text, len)
     cpp_reader *pfile;
     unsigned char *text;
     unsigned int len;
{
  cpp_token *token = _cpp_temp_token (pfile);

  text[len] = '\0';
  token->type = CPP_STRING;
  token->val.str.len = len;
  token->val.str.text = text;
  token->flags = 0;
  return token;
}

/* Allocates and returns a CPP_NUMBER token evaluating to NUMBER.  */
static const cpp_token *
new_number_token (pfile, number)
     cpp_reader *pfile;
     int number;
{
  cpp_token *token = _cpp_temp_token (pfile);
  unsigned char *buf = _cpp_pool_alloc (&pfile->ident_pool, 20);

  sprintf ((char *) buf, "%d", number);
  token->type = CPP_NUMBER;
  token->val.str.text = buf;
  token->val.str.len = ustrlen (buf);
  token->flags = 0;
  return token;
}

static const char * const monthnames[] =
{
  "Jan", "Feb", "Mar", "Apr", "May", "Jun",
  "Jul", "Aug", "Sep", "Oct", "Nov", "Dec"
};

/* Handle builtin macros like __FILE__.  */
static const cpp_token *
builtin_macro (pfile, node)
     cpp_reader *pfile;
     cpp_hashnode *node;
{
  switch (node->value.builtin)
    {
    default:
      cpp_ice (pfile, "invalid builtin macro \"%s\"", NODE_NAME (node));
      return new_number_token (pfile, 1);

    case BT_FILE:
    case BT_BASE_FILE:
      {
	unsigned int len;
	const char *name;
	U_CHAR *buf;
	const struct line_map *map = pfile->map;

	if (node->value.builtin == BT_BASE_FILE)
	  while (! MAIN_FILE_P (map))
	    map = INCLUDED_FROM (&pfile->line_maps, map);

	name = map->to_file;
	len = strlen (name);
	buf = _cpp_pool_alloc (&pfile->ident_pool, len * 4 + 1);
	len = quote_string (buf, (const unsigned char *) name, len) - buf;

	return new_string_token (pfile, buf, len);
      }
	
    case BT_INCLUDE_LEVEL:
      /* The line map depth counts the primary source as level 1, but
	 historically __INCLUDE_DEPTH__ has called the primary source
	 level 0.  */
      return new_number_token (pfile, pfile->line_maps.depth - 1);

    case BT_SPECLINE:
      /* If __LINE__ is embedded in a macro, it must expand to the
	 line of the macro's invocation, not its definition.
	 Otherwise things like assert() will not work properly.  */
      return new_number_token (pfile, SOURCE_LINE (pfile->map,
						   pfile->cur_token[-1].line));

    case BT_STDC:
      {
	int stdc = (!CPP_IN_SYSTEM_HEADER (pfile)
		    || pfile->spec_nodes.n__STRICT_ANSI__->type != NT_VOID);
	return new_number_token (pfile, stdc);
      }

    case BT_DATE:
    case BT_TIME:
      if (pfile->date.type == CPP_EOF)
	{
	  /* Allocate __DATE__ and __TIME__ strings from permanent
	     storage.  We only do this once, and don't generate them
	     at init time, because time() and localtime() are very
	     slow on some systems.  */
	  time_t tt = time (NULL);
	  struct tm *tb = localtime (&tt);

	  pfile->date.val.str.text =
	    _cpp_pool_alloc (&pfile->ident_pool, sizeof ("Oct 11 1347"));
	  pfile->date.val.str.len = sizeof ("Oct 11 1347") - 1;
	  pfile->date.type = CPP_STRING;
	  pfile->date.flags = 0;
	  sprintf ((char *) pfile->date.val.str.text, "%s %2d %4d",
		   monthnames[tb->tm_mon], tb->tm_mday, tb->tm_year + 1900);

	  pfile->time.val.str.text =
	    _cpp_pool_alloc (&pfile->ident_pool, sizeof ("12:34:56"));
	  pfile->time.val.str.len = sizeof ("12:34:56") - 1;
	  pfile->time.type = CPP_STRING;
	  pfile->time.flags = 0;
	  sprintf ((char *) pfile->time.val.str.text, "%02d:%02d:%02d",
		   tb->tm_hour, tb->tm_min, tb->tm_sec);
	}

      return node->value.builtin == BT_DATE ? &pfile->date: &pfile->time;
    }
}

/* Adds backslashes before all backslashes and double quotes appearing
   in strings.  Non-printable characters are converted to octal.  */
static U_CHAR *
quote_string (dest, src, len)
     U_CHAR *dest;
     const U_CHAR *src;
     unsigned int len;
{
  while (len--)
    {
      U_CHAR c = *src++;

      if (c == '\\' || c == '"')
	{
	  *dest++ = '\\';
	  *dest++ = c;
	}
      else
	{
	  if (ISPRINT (c))
	    *dest++ = c;
	  else
	    {
	      sprintf ((char *) dest, "\\%03o", c);
	      dest += 4;
	    }
	}
    }

  return dest;
}

/* Convert a token sequence to a single string token according to the
   rules of the ISO C #-operator.  */
static const cpp_token *
stringify_arg (pfile, arg)
     cpp_reader *pfile;
     macro_arg *arg;
{
  cpp_pool *pool = &pfile->ident_pool;
  unsigned char *start = POOL_FRONT (pool);
  unsigned int i, escape_it, total_len = 0, backslash_count = 0;
  const cpp_token *source = NULL;

  /* Loop, reading in the argument's tokens.  */
  for (i = 0; i < arg->count; i++)
    {
      unsigned char *dest;
      const cpp_token *token = arg->first[i];
      unsigned int len;

      if (token->type == CPP_PADDING)
	{
	  if (source == NULL)
	    source = token->val.source;
	  continue;
	}

      escape_it = (token->type == CPP_STRING || token->type == CPP_WSTRING
		   || token->type == CPP_CHAR || token->type == CPP_WCHAR);

      len = cpp_token_len (token);
      if (escape_it)
	/* Worst case is each char is octal.  */
	len *= 4;
      len += 2;			/* Room for initial space and final NUL.  */

      dest = &start[total_len];
      if (dest + len > POOL_LIMIT (pool))
	{
	  _cpp_next_chunk (pool, len, (unsigned char **) &start);
	  dest = &start[total_len];
	}

      /* Leading white space?  */
      if (total_len)
	{
	  if (source == NULL)
	    source = token;
	  if (source->flags & PREV_WHITE)
	    *dest++ = ' ';
	}
      source = NULL;

      if (escape_it)
	{
	  unsigned char *buf = (unsigned char *) xmalloc (len);

	  len = cpp_spell_token (pfile, token, buf) - buf;
	  dest = quote_string (dest, buf, len);
	  free (buf);
	}
      else
	dest = cpp_spell_token (pfile, token, dest);
      total_len = dest - start;

      if (token->type == CPP_OTHER && token->val.c == '\\')
	backslash_count++;
      else
	backslash_count = 0;
    }

  /* Ignore the final \ of invalid string literals.  */
  if (backslash_count & 1)
    {
      cpp_warning (pfile, "invalid string literal, ignoring final '\\'");
      total_len--;
    }

  /* Commit the memory, including NUL, and return the token.  */
  POOL_COMMIT (pool, total_len + 1);
  return new_string_token (pfile, start, total_len);
}

/* Try to paste two tokens.  On success, return non-zero.  In any
   case, PLHS is updated to point to the pasted token, which is
   guaranteed to not have the PASTE_LEFT flag set.  */
static bool
paste_tokens (pfile, plhs, rhs)
     cpp_reader *pfile;
     const cpp_token **plhs, *rhs;
{
  unsigned char *buf, *end;
  const cpp_token *lhs;
  unsigned int len;
  bool valid;

  lhs = *plhs;
  len = cpp_token_len (lhs) + cpp_token_len (rhs) + 1;
  buf = (unsigned char *) alloca (len);
  end = cpp_spell_token (pfile, lhs, buf);

  /* Avoid comment headers, since they are still processed in stage 3.
     It is simpler to insert a space here, rather than modifying the
     lexer to ignore comments in some circumstances.  Simply returning
     false doesn't work, since we want to clear the PASTE_LEFT flag.  */
  if (lhs->type == CPP_DIV
      && (rhs->type == CPP_MULT || rhs->type == CPP_DIV))
    *end++ = ' ';
  end = cpp_spell_token (pfile, rhs, end);

  cpp_push_buffer (pfile, buf, end - buf, /* from_stage3 */ true, 1);

  /* Tweak the column number the lexer will report.  */
  pfile->buffer->col_adjust = pfile->cur_token[-1].col - 1;

  /* We don't want a leading # to be interpreted as a directive.  */
  pfile->buffer->saved_flags = 0;

  /* Set pfile->cur_token as required by _cpp_lex_direct.  */
  pfile->cur_token = _cpp_temp_token (pfile);
  *plhs = _cpp_lex_direct (pfile);
  valid = (pfile->buffer->cur == pfile->buffer->rlimit
	   && pfile->buffer->read_ahead == EOF);
  _cpp_pop_buffer (pfile);

  return valid;
}

/* Handles an arbitrarily long sequence of ## operators.  This
   implementation is left-associative, non-recursive, and finishes a
   paste before handling succeeding ones.  If the paste fails, we back
   up a token to just after the ## operator, with the effect that it
   appears in the output stream normally.  */
static void
paste_all_tokens (pfile, lhs)
     cpp_reader *pfile;
     const cpp_token *lhs;
{
  const cpp_token *rhs;
  cpp_context *context = pfile->context;

  do
    {
      /* Take the token directly from the current context.  We can do
	 this, because we are in the replacement list of either an
	 object-like macro, or a function-like macro with arguments
	 inserted.  In either case, the constraints to #define
	 guarantee we have at least one more token.  */
      if (context->direct_p)
	rhs = context->first.token++;
      else
	rhs = *context->first.ptoken++;

      if (rhs->type == CPP_PADDING)
	abort ();

      if (!paste_tokens (pfile, &lhs, rhs))
	{
	  _cpp_backup_tokens (pfile, 1);

	  /* Mandatory warning for all apart from assembler.  */
	  if (CPP_OPTION (pfile, lang) != CLK_ASM)
	    cpp_warning (pfile,
	 "pasting \"%s\" and \"%s\" does not give a valid preprocessing token",
			 cpp_token_as_text (pfile, lhs),
			 cpp_token_as_text (pfile, rhs));
	  break;
	}
    }
  while (rhs->flags & PASTE_LEFT);

  /* Put the resulting token in its own context.  */
  push_token_context (pfile, NULL, lhs, 1);
}

/* Reads and returns the arguments to a function-like macro invocation.
   Assumes the opening parenthesis has been processed.  If there is an
   error, emits an appropriate diagnostic and returns NULL.  */
static _cpp_buff *
collect_args (pfile, node)
     cpp_reader *pfile;
     const cpp_hashnode *node;
{
  _cpp_buff *buff, *base_buff;
  cpp_macro *macro;
  macro_arg *args, *arg;
  const cpp_token *token;
  unsigned int argc;
  bool error = false;

  macro = node->value.macro;
  if (macro->paramc)
    argc = macro->paramc;
  else
    argc = 1;
  buff = _cpp_get_buff (pfile, argc * (50 * sizeof (cpp_token *)
				       + sizeof (macro_arg)));
  base_buff = buff;
  args = (macro_arg *) buff->base;
  memset (args, 0, argc * sizeof (macro_arg));
  buff->cur = (char *) &args[argc];
  arg = args, argc = 0;

  /* Collect the tokens making up each argument.  We don't yet know
     how many arguments have been supplied, whether too many or too
     few.  Hence the slightly bizarre usage of "argc" and "arg".  */
  do
    {
      unsigned int paren_depth = 0;
      unsigned int ntokens = 0;

      argc++;
      arg->first = (const cpp_token **) buff->cur;

      for (;;)
	{
	  /* Require space for 2 new tokens (including a CPP_EOF).  */
	  if ((char *) &arg->first[ntokens + 2] > buff->limit)
	    {
	      buff = _cpp_extend_buff (pfile, buff,
				       1000 * sizeof (cpp_token *));
	      arg->first = (const cpp_token **) buff->cur;
	    }

	  token = cpp_get_token (pfile);

	  if (token->type == CPP_PADDING)
	    {
	      /* Drop leading padding.  */
	      if (ntokens == 0)
		continue;
	    }
	  else if (token->type == CPP_OPEN_PAREN)
	    paren_depth++;
	  else if (token->type == CPP_CLOSE_PAREN)
	    {
	      if (paren_depth-- == 0)
		break;
	    }
	  else if (token->type == CPP_COMMA)
	    {
	      /* A comma does not terminate an argument within
		 parentheses or as part of a variable argument.  */
	      if (paren_depth == 0
		  && ! (macro->variadic && argc == macro->paramc))
		break;
	    }
	  else if (token->type == CPP_EOF
		   || (token->type == CPP_HASH && token->flags & BOL))
	    break;

	  arg->first[ntokens++] = token;
	}

      /* Drop trailing padding.  */
      while (ntokens > 0 && arg->first[ntokens - 1]->type == CPP_PADDING)
	ntokens--;

      arg->count = ntokens;
      arg->first[ntokens] = &pfile->eof;

      /* Terminate the argument.  Excess arguments loop back and
	 overwrite the final legitimate argument, before failing.  */
      if (argc <= macro->paramc)
	{
	  buff->cur = (char *) &arg->first[ntokens + 1];
	  if (argc != macro->paramc)
	    arg++;
	}
    }
  while (token->type != CPP_CLOSE_PAREN
	 && token->type != CPP_EOF
	 && token->type != CPP_HASH);

  if (token->type == CPP_EOF || token->type == CPP_HASH)
    {
      bool step_back = false;

      /* 6.10.3 paragraph 11: If there are sequences of preprocessing
	 tokens within the list of arguments that would otherwise act
	 as preprocessing directives, the behavior is undefined.

	 This implementation will report a hard error, terminate the
	 macro invocation, and proceed to process the directive.  */
      if (token->type == CPP_HASH)
	{
	  cpp_error (pfile,
		     "directives may not be used inside a macro argument");
	  step_back = true;
	}
      else
	/* We still need the CPP_EOF to end directives, and to end
           pre-expansion of a macro argument.  */
	step_back = (pfile->context->prev || pfile->state.in_directive);

      if (step_back)
	_cpp_backup_tokens (pfile, 1);
      cpp_error (pfile, "unterminated argument list invoking macro \"%s\"",
		 NODE_NAME (node));
      error = true;
    }
  else if (argc < macro->paramc)
    {
      /* As an extension, a rest argument is allowed to not appear in
	 the invocation at all.
	 e.g. #define debug(format, args...) something
	 debug("string");
	 
	 This is exactly the same as if there had been an empty rest
	 argument - debug("string", ).  */

      if (argc + 1 == macro->paramc && macro->variadic)
	{
	  if (CPP_PEDANTIC (pfile) && ! macro->syshdr)
	    cpp_pedwarn (pfile, "ISO C99 requires rest arguments to be used");
	}
      else
	{
	  cpp_error (pfile,
		     "macro \"%s\" requires %u arguments, but only %u given",
		     NODE_NAME (node), macro->paramc, argc);
	  error = true;
	}
    }
  else if (argc > macro->paramc)
    {
      /* Empty argument to a macro taking no arguments is OK.  */
      if (argc != 1 || arg->count)
	{
	  cpp_error (pfile,
		     "macro \"%s\" passed %u arguments, but takes just %u",
		     NODE_NAME (node), argc, macro->paramc);
	  error = true;
	}
    }

  if (!error)
    return base_buff;

  _cpp_release_buff (pfile, base_buff);
  return NULL;
}

static int
funlike_invocation_p (pfile, node)
     cpp_reader *pfile;
     const cpp_hashnode *node;
{
  const cpp_token *maybe_paren;
  _cpp_buff *buff = NULL;

  pfile->state.prevent_expansion++;
  pfile->keep_tokens++;

  pfile->state.parsing_args = 1;
  do
    maybe_paren = cpp_get_token (pfile);
  while (maybe_paren->type == CPP_PADDING);
  pfile->state.parsing_args = 2;

  if (maybe_paren->type == CPP_OPEN_PAREN)
    buff = collect_args (pfile, node);
  else
    {
      _cpp_backup_tokens (pfile, 1);
      if (CPP_WTRADITIONAL (pfile) && ! node->value.macro->syshdr)
	cpp_warning (pfile,
 "function-like macro \"%s\" must be used with arguments in traditional C",
		     NODE_NAME (node));
    }

  pfile->state.parsing_args = 0;
  pfile->keep_tokens--;
  pfile->state.prevent_expansion--;

  if (buff)
    {
      if (node->value.macro->paramc > 0)
	replace_args (pfile, node->value.macro, (macro_arg *) buff->base);
      _cpp_release_buff (pfile, buff);
    }

  return buff != 0;
}

/* Push the context of a macro onto the context stack.  TOKEN is the
   macro name.  If we can successfully start expanding the macro,
   TOKEN is replaced with the first token of the expansion, and we
   return non-zero.  */
static int
enter_macro_context (pfile, node)
     cpp_reader *pfile;
     cpp_hashnode *node;
{
  if (node->flags & NODE_BUILTIN)
    push_token_context (pfile, NULL, builtin_macro (pfile, node), 1);
  else
    {
      cpp_macro *macro = node->value.macro;

      if (macro->fun_like && !funlike_invocation_p (pfile, node))
	return 0;

      /* Disable the macro within its expansion.  */
      macro->disabled = 1;

      if (macro->paramc == 0)
	push_token_context (pfile, macro, macro->expansion, macro->count);
    }
 
  return 1;
}

/* Take the expansion of a function-like MACRO, replacing parameters
   with the actual arguments.  Each argument is macro-expanded before
   replacement, unless operated upon by the # or ## operators.  */
static void
replace_args (pfile, macro, args)
     cpp_reader *pfile;
     cpp_macro *macro;
     macro_arg *args;
{
  unsigned int i, total;
  const cpp_token *src, *limit;
  const cpp_token **dest, **first;
  macro_arg *arg;
  _cpp_buff *buff;

  /* First, fully macro-expand arguments, calculating the number of
     tokens in the final expansion as we go.  The ordering of the if
     statements below is subtle; we must handle stringification before
     pasting.  */
  total = macro->count;
  limit = macro->expansion + macro->count;

  for (src = macro->expansion; src < limit; src++)
    if (src->type == CPP_MACRO_ARG)
      {
	/* Leading and trailing padding tokens.  */
	total += 2;

	/* We have an argument.  If it is not being stringified or
	   pasted it is macro-replaced before insertion.  */
	arg = &args[src->val.arg_no - 1];

	if (src->flags & STRINGIFY_ARG)
	  {
	    if (!arg->stringified)
	      arg->stringified = stringify_arg (pfile, arg);
	  }
	else if ((src->flags & PASTE_LEFT)
		 || (src > macro->expansion && (src[-1].flags & PASTE_LEFT)))
	  total += arg->count - 1;
	else
	  {
	    if (!arg->expanded)
	      expand_arg (pfile, arg);
	    total += arg->expanded_count - 1;
	  }
      }

  /* Now allocate space for the expansion, copy the tokens and replace
     the arguments.  */
  buff = _cpp_get_buff (pfile, total * sizeof (cpp_token *));
  first = (const cpp_token **) buff->base;
  dest = first;

  for (src = macro->expansion; src < limit; src++)
    {
      unsigned int count;
      const cpp_token **from, **paste_flag;

      if (src->type != CPP_MACRO_ARG)
	{
	  *dest++ = src;
	  continue;
	}

      paste_flag = 0;
      arg = &args[src->val.arg_no - 1];
      if (src->flags & STRINGIFY_ARG)
	count = 1, from = &arg->stringified;
      else if (src->flags & PASTE_LEFT)
	count = arg->count, from = arg->first;
      else if (src != macro->expansion && (src[-1].flags & PASTE_LEFT))
	{
	  count = arg->count, from = arg->first;
	  if (dest != first)
	    {
	      /* GCC has special semantics for , ## b where b is a
		 varargs parameter: the comma disappears if b was
		 given no actual arguments (not merely if b is an
		 empty argument); otherwise the paste flag is removed.  */
	      if (dest[-1]->type == CPP_COMMA
		  && macro->variadic
		  && src->val.arg_no == macro->paramc)
		{
		  if (count == 0)
		    dest--;
		  else
		    paste_flag = dest - 1;
		}
	      /* Remove the paste flag if the RHS is a placemarker.  */
	      else if (count == 0)
		paste_flag = dest - 1;
	    }
	}
      else
	count = arg->expanded_count, from = arg->expanded;

      /* Padding on the left of an argument (unless RHS of ##).  */
      if (!pfile->state.in_directive
	  && src != macro->expansion && !(src[-1].flags & PASTE_LEFT))
	*dest++ = padding_token (pfile, src);

      if (count)
	{
	  memcpy (dest, from, count * sizeof (cpp_token *));
	  dest += count;

	  /* With a non-empty argument on the LHS of ##, the last
	     token should be flagged PASTE_LEFT.  */
	  if (src->flags & PASTE_LEFT)
	    paste_flag = dest - 1;
	}

      /* Avoid paste on RHS (even case count == 0).  */
      if (!pfile->state.in_directive && !(src->flags & PASTE_LEFT))
	*dest++ = &pfile->avoid_paste;

      /* Add a new paste flag, or remove an unwanted one.  */
      if (paste_flag)
	{
	  cpp_token *token = _cpp_temp_token (pfile);
	  token->type = (*paste_flag)->type;
	  token->val.str = (*paste_flag)->val.str;
	  if (src->flags & PASTE_LEFT)
	    token->flags = (*paste_flag)->flags | PASTE_LEFT;
	  else
	    token->flags = (*paste_flag)->flags & ~PASTE_LEFT;
	  *paste_flag = token;
	}
    }

  /* Free the expanded arguments.  */
  for (i = 0; i < macro->paramc; i++)
    if (args[i].expanded)
      free (args[i].expanded);

  push_ptoken_context (pfile, macro, buff, first, dest - first);
}

/* Return a special padding token, with padding inherited from SOURCE.  */
static const cpp_token *
padding_token (pfile, source)
     cpp_reader *pfile;
     const cpp_token *source;
{
  cpp_token *result = _cpp_temp_token (pfile);

  result->type = CPP_PADDING;
  result->val.source = source;
  result->flags = 0;
  return result;
}

/* Move to the next context.  Create one if there is none.  */
static cpp_context *
next_context (pfile)
     cpp_reader *pfile;
{
  cpp_context *result = pfile->context->next;

  if (result == 0)
    {
      result = xnew (cpp_context);
      result->prev = pfile->context;
      result->next = 0;
      pfile->context->next = result;
    }

  pfile->context = result;
  return result;
}

/* Push a list of pointers to tokens.  */
static void
push_ptoken_context (pfile, macro, buff, first, count)
     cpp_reader *pfile;
     cpp_macro *macro;
     _cpp_buff *buff;
     const cpp_token **first;
     unsigned int count;
{
  cpp_context *context = next_context (pfile);

  context->direct_p = false;
  context->macro = macro;
  context->buff = buff;
  context->first.ptoken = first;
  context->last.ptoken = first + count;
}

/* Push a list of tokens.  */
static void
push_token_context (pfile, macro, first, count)
     cpp_reader *pfile;
     cpp_macro *macro;
     const cpp_token *first;
     unsigned int count;
{
  cpp_context *context = next_context (pfile);

  context->direct_p = true;
  context->macro = macro;
  context->buff = NULL;
  context->first.token = first;
  context->last.token = first + count;
}

static void
expand_arg (pfile, arg)
     cpp_reader *pfile;
     macro_arg *arg;
{
  unsigned int capacity;

  if (arg->count == 0)
    return;

  /* Loop, reading in the arguments.  */
  capacity = 256;
  arg->expanded = (const cpp_token **)
    xmalloc (capacity * sizeof (cpp_token *));

  push_ptoken_context (pfile, NULL, NULL, arg->first, arg->count + 1);
  for (;;)
    {
      const cpp_token *token;

      if (arg->expanded_count + 1 >= capacity)
	{
	  capacity *= 2;
	  arg->expanded = (const cpp_token **)
	    xrealloc (arg->expanded, capacity * sizeof (cpp_token *));
	}

      token = cpp_get_token (pfile);

      if (token->type == CPP_EOF)
	break;

      arg->expanded[arg->expanded_count++] = token;
    }

  _cpp_pop_context (pfile);
}

void
_cpp_pop_context (pfile)
     cpp_reader *pfile;
{
  cpp_context *context = pfile->context;

  /* Re-enable a macro when leaving its expansion.  */
  if (context->macro)
    context->macro->disabled = 0;

  if (context->buff)
    _cpp_release_buff (pfile, context->buff);

  pfile->context = context->prev;
}

/* Eternal routine to get a token.  Also used nearly everywhere
   internally, except for places where we know we can safely call
   the lexer directly, such as lexing a directive name.

   Macro expansions and directives are transparently handled,
   including entering included files.  Thus tokens are post-macro
   expansion, and after any intervening directives.  External callers
   see CPP_EOF only at EOF.  Internal callers also see it when meeting
   a directive inside a macro call, when at the end of a directive and
   state.in_directive is still 1, and at the end of argument
   pre-expansion.  */
const cpp_token *
cpp_get_token (pfile)
     cpp_reader *pfile;
{
  const cpp_token *result;

  for (;;)
    {
      cpp_hashnode *node;
      cpp_context *context = pfile->context;

      /* Context->prev == 0 <=> base context.  */
      if (!context->prev)
	result = _cpp_lex_token (pfile);
      else if (context->first.token != context->last.token)
	{
	  if (context->direct_p)
	    result = context->first.token++;
	  else
	    result = *context->first.ptoken++;

	  if (result->flags & PASTE_LEFT)
	    {
	      paste_all_tokens (pfile, result);
	      if (pfile->state.in_directive)
		continue;
	      return padding_token (pfile, result);
	    }
	}
      else
	{
	  _cpp_pop_context (pfile);
	  if (pfile->state.in_directive)
	    continue;
	  return &pfile->avoid_paste;
	}

      if (result->type != CPP_NAME)
	break;

      node = result->val.node;

      /* Handle macros and the _Pragma operator.  */
      if (node->type == NT_MACRO && !(result->flags & NO_EXPAND))
	{
	  /* Macros invalidate controlling macros.  */
	  pfile->mi_valid = false;

	  if (!(node->flags & NODE_BUILTIN) && node->value.macro->disabled)
	    {
	      /* Flag this token as always unexpandable.  */
	      cpp_token *t = _cpp_temp_token (pfile);
	      t->type = result->type;
	      t->flags = result->flags | NO_EXPAND;
	      t->val.str = result->val.str;
	      result = t;
	    }
	  else if (!pfile->state.prevent_expansion
		   && enter_macro_context (pfile, node))
	    {
	      if (pfile->state.in_directive)
		continue;
	      return padding_token (pfile, result);
	    }
	}