n_lex_input(): truly support line continuation via backslash..

[s-mailx.git] / lex_input.c

/*@ S-nail - a mail user agent derived from Berkeley Mail.
 *@ Command input, lexing and evaluation, resource file loading and `source'ing.
 *@ TODO PS_ROBOT requires yet PS_SOURCING, which REALLY sucks.
 *@ TODO Commands and ghosts deserve a hashmap.  Or so.
 *
 * Copyright (c) 2000-2004 Gunnar Ritter, Freiburg i. Br., Germany.
 * Copyright (c) 2012 - 2015 Steffen (Daode) Nurpmeso <sdaoden@users.sf.net>.
 */
/*
 * Copyright (c) 1980, 1993
 *      The Regents of the University of California.  All rights reserved.
 *
 * Redistribution and use in source and binary forms, with or without
 * modification, are permitted provided that the following conditions
 * are met:
 * 1. Redistributions of source code must retain the above copyright
 *    notice, this list of conditions and the following disclaimer.
 * 2. Redistributions in binary form must reproduce the above copyright
 *    notice, this list of conditions and the following disclaimer in the
 *    documentation and/or other materials provided with the distribution.
 * 3. Neither the name of the University nor the names of its contributors
 *    may be used to endorse or promote products derived from this software
 *    without specific prior written permission.
 *
 * THIS SOFTWARE IS PROVIDED BY THE REGENTS AND CONTRIBUTORS ``AS IS'' AND
 * ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT LIMITED TO, THE
 * IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS FOR A PARTICULAR PURPOSE
 * ARE DISCLAIMED.  IN NO EVENT SHALL THE REGENTS OR CONTRIBUTORS BE LIABLE
 * FOR ANY DIRECT, INDIRECT, INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL
 * DAMAGES (INCLUDING, BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS
 * OR SERVICES; LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION)
 * HOWEVER CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
 * LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN ANY WAY
 * OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE POSSIBILITY OF
 * SUCH DAMAGE.
 */
#undef n_FILE
#define n_FILE lex_input

#ifndef HAVE_AMALGAMATION
# include "nail.h"
#endif

enum a_lex_input_flags{
   a_LEX_NONE,
   a_LEX_FREE = 1<<0,            /* Structure was allocated, free() it */
   a_LEX_PIPE = 1<<1,            /* Open on a pipe */
   a_LEX_MACRO = 1<<2,           /* Running a macro */
   a_LEX_MACRO_FREE_DATA = 1<<3, /* Lines are allocated, free(3) once done */
   a_LEX_MACRO_X_OPTION = 1<<4,  /* Macro indeed command line -X option */
   a_LEX_MACRO_CMD = 1<<5,       /* Macro indeed single-line: ~:COMMAND */

   a_LEX_SUPER_MACRO = 1<<16     /* *Not* inheriting PS_SOURCING state */
};

struct a_lex_cmd{
   char const *lc_name;       /* Name of command */
   int (*lc_func)(void*);     /* Implementor of command */
   enum argtype lc_argtype;   /* Arglist type (see below) */
   si16_t lc_msgflag;         /* Required flags of msgs */
   si16_t lc_msgmask;         /* Relevant flags of msgs */
#ifdef HAVE_DOCSTRINGS
   char const *lc_doc;        /* One line doc for command */
#endif
};
/* Yechh, can't initialize unions */
#define lc_minargs lc_msgflag /* Minimum argcount for RAWLIST */
#define lc_maxargs lc_msgmask /* Max argcount for RAWLIST */

struct a_lex_ghost{
   struct a_lex_ghost *lg_next;
   struct str lg_cmd;            /* Data follows after .lg_name */
   char lg_name[VFIELD_SIZE(0)];
};

struct a_lex_eval_ctx{
   struct str le_line;           /* The terminated data to _evaluate() */
   ui32_t le_line_size;          /* May be used to store line memory size */
   bool_t le_is_recursive;       /* Evaluation in evaluation? (collect ~:) */
   ui8_t __dummy[3];
   bool_t le_add_history;        /* Enter (final) command in history? */
   char const *le_new_content;   /* History: reenter line, start with this */
};

struct a_lex_input_stack{
   struct a_lex_input_stack *li_outer;
   FILE *li_file;                /* File we were in */
   void *li_cond;                /* Saved state of conditional stack */
   ui32_t li_flags;              /* enum a_lex_input_flags */
   ui32_t li_loff;               /* Pseudo (macro): index in .li_lines */
   char **li_lines;              /* Pseudo content, lines unfolded */
   char li_name[VFIELD_SIZE(0)]; /* Name of file or macro */
};

static bool_t a_lex_reset_on_stop;        /* do a reset() if stopped */
static sighandler_type a_lex_oldpipe;
static struct a_lex_ghost *a_lex_ghosts;
/* a_lex_cmd_tab[] after fun protos */

/* */
static struct a_lex_input_stack *a_lex_input;

/* Isolate the command from the arguments */
static char *a_lex_isolate(char const *comm);

/* Command ghost handling */
static int a_lex_c_ghost(void *v);
static int a_lex_c_unghost(void *v);

/* Print a list of all commands */
static int a_lex_c_list(void *v);

static int a_lex__pcmd_cmp(void const *s1, void const *s2);

/* `quit' command */
static int a_lex_c_quit(void *v);

/* Print the binaries compiled-in features */
static int a_lex_c_features(void *v);

/* Print the binaries version number */
static int a_lex_c_version(void *v);

/* Evaluate a single command.
 * .le_add_history and .le_new_content will be updated upon success.
 * Command functions return 0 for success, 1 for error, and -1 for abort.
 * 1 or -1 aborts a load or source, a -1 aborts the interactive command loop */
static int a_lex_evaluate(struct a_lex_eval_ctx *evp);

/* Get first-fit, or NULL */
static struct a_lex_cmd const *a_lex__firstfit(char const *comm);

/* When we wake up after ^Z, reprint the prompt */
static void a_lex_stop(int s);

/* Branch here on hangup signal and simulate "exit" */
static void a_lex_hangup(int s);

/* The following gets called on receipt of an interrupt.  Close all open files
 * except 0, 1, 2, and the temporary.  Also, unstack all source files */
static void a_lex_onintr(int s);

/* Pop the current input back to the previous level.  Update the program state.
 * If the argument is TRUM1 then we don't alert and error out if the stack
 * doesn't exist at all */
static void a_lex_unstack(bool_t eval_error);

/* `source' and `source_if' (if silent_error: no pipes allowed, then) */
static bool_t a_lex_source_file(char const *file, bool_t silent_error);

/* System resource file load()ing or -X command line option array traversal */
static bool_t a_lex_load(struct a_lex_input_stack *lip);

/* A simplified command loop for recursed state machines */
static bool_t a_commands_recursive(void);

/* List of all commands, and list of commands which are specially treated
 * and deduced in _evaluate(), but we need a list for _c_list() and
 * print_comm_docstr() */
#ifdef HAVE_DOCSTRINGS
# define DS(S) , S
#else
# define DS(S)
#endif
static struct a_lex_cmd const a_lex_cmd_tab[] = {
#include "cmd_tab.h"
},
      a_lex_special_cmd_tab[] = {
   { "#", NULL, 0, 0, 0
      DS(N_("\"Comment command\": ignore remaining (continuable) line")) },
   { "-", NULL, 0, 0, 0
      DS(N_("Print out the preceding message")) }
};
#undef DS

static char *
a_lex_isolate(char const *comm){
   NYD2_ENTER;
   while(*comm != '\0' &&
         strchr("~|? \t0123456789&%@$^.:/-+*'\",;(`", *comm) == NULL)
      ++comm;
   NYD2_LEAVE;
   return UNCONST(comm);
}

static int
a_lex_c_ghost(void *v){
   struct a_lex_ghost *lgp, *gp;
   size_t i, cl, nl;
   char *cp;
   char const **argv;
   NYD_ENTER;

   argv = v;

   /* Show the list? */
   if(*argv == NULL){
      FILE *fp;

      if((fp = Ftmp(NULL, "ghost", OF_RDWR | OF_UNLINK | OF_REGISTER)) == NULL)
         fp = stdout;

      for(i = 0, gp = a_lex_ghosts; gp != NULL; gp = gp->lg_next)
         fprintf(fp, "ghost %s \"%s\"\n",
            gp->lg_name, string_quote(gp->lg_cmd.s));

      if(fp != stdout){
         page_or_print(fp, i);
         Fclose(fp);
      }
      goto jleave;
   }

   /* Verify the ghost name is a valid one */
   if(*argv[0] == '\0' || *a_lex_isolate(argv[0]) != '\0'){
      n_err(_("`ghost': can't canonicalize \"%s\"\n"), argv[0]);
      v = NULL;
      goto jleave;
   }

   /* Show command of single ghost? */
   if(argv[1] == NULL){
      for(gp = a_lex_ghosts; gp != NULL; gp = gp->lg_next)
         if(!strcmp(argv[0], gp->lg_name)){
            printf("ghost %s \"%s\"\n",
               gp->lg_name, string_quote(gp->lg_cmd.s));
            goto jleave;
         }
      n_err(_("`ghost': no such alias: \"%s\"\n"), argv[0]);
      v = NULL;
      goto jleave;
   }

   /* Define command for ghost: verify command content */
   for(cl = 0, i = 1; (cp = UNCONST(argv[i])) != NULL; ++i)
      if(*cp != '\0')
         cl += strlen(cp) +1; /* SP or NUL */
   if(cl == 0){
      n_err(_("`ghost': empty command arguments after \"%s\"\n"), argv[0]);
      v = NULL;
      goto jleave;
   }

   /* If the ghost already exists, recreate */
   for(lgp = NULL, gp = a_lex_ghosts; gp != NULL; lgp = gp, gp = gp->lg_next)
      if(!strcmp(gp->lg_name, argv[0])){
         if(lgp != NULL)
            lgp->lg_next = gp->lg_next;
         else
            a_lex_ghosts = gp->lg_next;
         free(gp);
         break;
      }

   nl = strlen(argv[0]) +1;
   gp = smalloc(sizeof(*gp) - VFIELD_SIZEOF(struct a_lex_ghost, lg_name) +
         nl + cl);
   gp->lg_next = a_lex_ghosts;
   a_lex_ghosts = gp;
   memcpy(gp->lg_name, argv[0], nl);
   cp = gp->lg_cmd.s = gp->lg_name + nl;
   gp->lg_cmd.l = --cl;

   while(*++argv != NULL)
      if((i = strlen(*argv)) > 0){
         memcpy(cp, *argv, i);
         cp += i;
         *cp++ = ' ';
      }
   *--cp = '\0';
jleave:
   NYD_LEAVE;
   return v == NULL;
}

static int
a_lex_c_unghost(void *v){
   struct a_lex_ghost *lgp, *gp;
   char const **argv, *cp;
   int rv;
   NYD_ENTER;

   rv = 0;
   argv = v;

   while((cp = *argv++) != NULL){
      if(cp[0] == '*' && cp[1] == '\0'){
         while((gp = a_lex_ghosts) != NULL){
            a_lex_ghosts = gp->lg_next;
            free(gp);
         }
      }else{
         for(lgp = NULL, gp = a_lex_ghosts; gp != NULL;
               lgp = gp, gp = gp->lg_next)
            if(!strcmp(gp->lg_name, cp)){
               if(lgp != NULL)
                  lgp->lg_next = gp->lg_next;
               else
                  a_lex_ghosts = gp->lg_next;
               free(gp);
               goto jouter;
            }
         n_err(_("`unghost': no such alias: \"%s\"\n"), cp);
         rv = 1;
jouter:  ;
      }
   }
   NYD_LEAVE;
   return rv;
}

static int
a_lex_c_list(void *v){
   struct a_lex_cmd const **cpa, *cp, **cursor;
   size_t i;
   NYD_ENTER;

   UNUSED(v);

   i = NELEM(a_lex_cmd_tab) + NELEM(a_lex_special_cmd_tab) + 1;
   cpa = ac_alloc(sizeof(cp) * i);

   for(i = 0; i < NELEM(a_lex_cmd_tab); ++i)
      cpa[i] = &a_lex_cmd_tab[i];
   /* C99 */{
      size_t j;

      for(j = 0; j < NELEM(a_lex_special_cmd_tab); ++i, ++j)
         cpa[i] = &a_lex_special_cmd_tab[j];
   }
   cpa[i] = NULL;

   qsort(cpa, i, sizeof(cp), &a_lex__pcmd_cmp);

   printf(_("Commands are:\n"));
   for(i = 0, cursor = cpa; (cp = *cursor++) != NULL;){
      size_t j;

      if(cp->lc_func == &c_cmdnotsupp)
         continue;
      j = strlen(cp->lc_name) + 2;
      if((i += j) > 72){
         i = j;
         printf("\n");
      }
      printf((*cursor != NULL ? "%s, " : "%s\n"), cp->lc_name);
   }

   ac_free(cpa);
   NYD_LEAVE;
   return 0;
}

static int
a_lex__pcmd_cmp(void const *s1, void const *s2){
   struct a_lex_cmd const * const *cp1, * const *cp2;
   int rv;
   NYD2_ENTER;

   cp1 = s1;
   cp2 = s2;
   rv = strcmp((*cp1)->lc_name, (*cp2)->lc_name);
   NYD2_LEAVE;
   return rv;
}

static int
a_lex_c_quit(void *v){
   NYD_ENTER;
   UNUSED(v);

   /* If we are PS_SOURCING, then return 1 so _evaluate() can handle it.
    * Otherwise return -1 to abort command loop */
   pstate |= PS_EXIT;
   NYD_LEAVE;
   return 0;
}

static int
a_lex_c_features(void *v){
   NYD_ENTER;

   UNUSED(v);

   printf(_("Features: %s\n"), ok_vlook(features));
   NYD_LEAVE;
   return 0;
}

static int
a_lex_c_version(void *v){
   NYD_ENTER;

   UNUSED(v);

   printf(_("Version %s\n"), ok_vlook(version));
   NYD_LEAVE;
   return 0;
}

static int
a_lex_evaluate(struct a_lex_eval_ctx *evp){
   /* xxx old style(9), but also old code */
   struct str line;
   char _wordbuf[2], *arglist[MAXARGC], *cp, *word;
   struct a_lex_ghost *gp;
   struct a_lex_cmd const *cmd;
   int c, e;
   NYD_ENTER;

   e = 1;
   cmd = NULL;
   gp = NULL;
   line = evp->le_line; /* XXX don't change original (buffer pointer) */
   assert(line.s[line.l] == '\0');
   evp->le_add_history = FAL0;
   evp->le_new_content = NULL;

   /* Command ghosts that refer to shell commands or macro expansion restart */
jrestart:

   /* Strip the white space away from end and beginning of command */
   if(line.l > 0){
      size_t i = line.l;

      for(cp = &line.s[i -1]; spacechar(*cp); --cp)
         --i;
      line.l = i;
   }
   for(cp = line.s; spacechar(*cp); ++cp)
      ;
   line.l -= PTR2SIZE(cp - line.s);

   /* Ignore null commands (comments) */
   if(*cp == '#')
      goto jleave0;

   /* Handle ! differently to get the correct lexical conventions */
   arglist[0] = cp;
   if(*cp == '!')
      ++cp;
   /* Isolate the actual command; since it may not necessarily be
    * separated from the arguments (as in `p1') we need to duplicate it to
    * be able to create a NUL terminated version.
    * We must be aware of several special one letter commands here */
   else if((cp = a_lex_isolate(cp)) == arglist[0] &&
         (*cp == '|' || *cp == '~' || *cp == '?'))
      ++cp;
   c = (int)PTR2SIZE(cp - arglist[0]);
   line.l -= c;
   word = UICMP(z, c, <, sizeof _wordbuf) ? _wordbuf : salloc(c +1);
   memcpy(word, arglist[0], c);
   word[c] = '\0';

   /* Look up the command; if not found, bitch.
    * Normally, a blank command would map to the first command in the
    * table; while PS_SOURCING, however, we ignore blank lines to eliminate
    * confusion; act just the same for ghosts */
   if(*word == '\0'){
      if((pstate & PS_ROBOT) || gp != NULL)
         goto jleave0;
      cmd = a_lex_cmd_tab + 0;
      goto jexec;
   }

   /* If this is the first evaluation, check command ghosts */
   if(gp == NULL){
      /* TODO relink list head, so it's sorted on usage over time?
       * TODO in fact, there should be one hashmap over all commands and ghosts
       * TODO so that the lookup could be made much more efficient than it is
       * TODO now (two adjacent list searches! */
      for(gp = a_lex_ghosts; gp != NULL; gp = gp->lg_next)
         if(!strcmp(word, gp->lg_name)){
            if(line.l > 0){
               size_t i;

               i = gp->lg_cmd.l;
               line.s = salloc(i + line.l +1);
               memcpy(line.s, gp->lg_cmd.s, i);
               memcpy(line.s + i, cp, line.l);
               line.s[i += line.l] = '\0';
               line.l = i;
            }else{
               line.s = gp->lg_cmd.s;
               line.l = gp->lg_cmd.l;
            }
            goto jrestart;
         }
   }

   if((cmd = a_lex__firstfit(word)) == NULL || cmd->lc_func == &c_cmdnotsupp){
      bool_t s;

      if(!(s = condstack_isskip()) || (options & OPT_D_V))
         n_err(_("Unknown command%s: `%s'\n"),
            (s ? _(" (ignored due to `if' condition)") : ""), word);
      if(s)
         goto jleave0;
      if(cmd != NULL){
         c_cmdnotsupp(NULL);
         cmd = NULL;
      }
      goto jleave;
   }

   /* See if we should execute the command -- if a conditional we always
    * execute it, otherwise, check the state of cond */
jexec:
   if(!(cmd->lc_argtype & ARG_F) && condstack_isskip())
      goto jleave0;

   /* Process the arguments to the command, depending on the type it expects */
   if(!(cmd->lc_argtype & ARG_M) && (options & OPT_SENDMODE)){
      n_err(_("May not execute `%s' while sending\n"), cmd->lc_name);
      goto jleave;
   }
   if((cmd->lc_argtype & ARG_S) && !(pstate & PS_STARTED)){
      n_err(_("May not execute `%s' during startup\n"), cmd->lc_name);
      goto jleave;
   }
   if((cmd->lc_argtype & ARG_I) &&
         !(options & (OPT_INTERACTIVE | OPT_BATCH_FLAG))){
      n_err(_("May not execute `%s' unless interactive or in batch mode\n"),
         cmd->lc_name);
      goto jleave;
   }
   if((cmd->lc_argtype & ARG_R) && (pstate & PS_RECURSED)){
      n_err(_("Cannot invoke `%s' when in recursed mode (e.g., composing)\n"),
         cmd->lc_name);
      goto jleave;
   }

   if((cmd->lc_argtype & ARG_W) && !(mb.mb_perm & MB_DELE)){
      n_err(_("May not execute `%s' -- message file is read only\n"),
         cmd->lc_name);
      goto jleave;
   }
   if((cmd->lc_argtype & ARG_A) && mb.mb_type == MB_VOID){
      n_err(_("Cannot execute `%s' without active mailbox\n"), cmd->lc_name);
      goto jleave;
   }

   if(cmd->lc_argtype & ARG_O)
      OBSOLETE2(_("this command will be removed"), cmd->lc_name);
   if(cmd->lc_argtype & ARG_V)
      temporary_arg_v_store = NULL;

   switch(cmd->lc_argtype & ARG_ARGMASK){
   case ARG_MSGLIST:
      /* Message list defaulting to nearest forward legal message */
      if(n_msgvec == NULL)
         goto je96;
      if((c = getmsglist(cp, n_msgvec, cmd->lc_msgflag)) < 0)
         break;
      if(c == 0){
         if((n_msgvec[0] = first(cmd->lc_msgflag, cmd->lc_msgmask)) != 0)
            n_msgvec[1] = 0;
      }
      if(n_msgvec[0] == 0){
         if(!(pstate & PS_HOOK_MASK))
            printf(_("No applicable messages\n"));
         break;
      }
      e = (*cmd->lc_func)(n_msgvec);
      break;

   case ARG_NDMLIST:
      /* Message list with no defaults, but no error if none exist */
      if(n_msgvec == NULL){
je96:
         n_err(_("Invalid use of \"message list\"\n"));
         break;
      }
      if((c = getmsglist(cp, n_msgvec, cmd->lc_msgflag)) < 0)
         break;
      e = (*cmd->lc_func)(n_msgvec);
      break;

   case ARG_STRLIST:
      /* Just the straight string, with leading blanks removed */
      while(whitechar(*cp))
         ++cp;
      e = (*cmd->lc_func)(cp);
      break;

   case ARG_RAWLIST:
   case ARG_ECHOLIST:
      /* A vector of strings, in shell style */
      if((c = getrawlist(cp, line.l, arglist, NELEM(arglist),
            ((cmd->lc_argtype & ARG_ARGMASK) == ARG_ECHOLIST))) < 0)
         break;
      if(c < cmd->lc_minargs){
         n_err(_("`%s' requires at least %d arg(s)\n"),
            cmd->lc_name, cmd->lc_minargs);
         break;
      }
#undef lc_minargs
      if(c > cmd->lc_maxargs){
         n_err(_("`%s' takes no more than %d arg(s)\n"),
            cmd->lc_name, cmd->lc_maxargs);
         break;
      }
#undef lc_maxargs
      e = (*cmd->lc_func)(arglist);
      break;

   case ARG_NOLIST:
      /* Just the constant zero, for exiting, eg. */
      e = (*cmd->lc_func)(0);
      break;

   default:
      DBG( n_panic(_("Implementation error: unknown argument type")); )
      goto jleave0;
   }

   if(e == 0 && (cmd->lc_argtype & ARG_V) &&
         (cp = temporary_arg_v_store) != NULL){
      temporary_arg_v_store = NULL;
      evp->le_new_content = cp;
      goto jleave0;
   }
   if(!(cmd->lc_argtype & ARG_H) && !(pstate & PS_MSGLIST_SAW_NO))
      evp->le_add_history = TRU1;

jleave:
   /* Exit the current source file on error TODO what a mess! */
   if(e == 0)
      pstate &= ~PS_EVAL_ERROR;
   else{
      pstate |= PS_EVAL_ERROR;
      if(e < 0 || (pstate & PS_ROBOT)){ /* FIXME */
         e = 1;
         goto jret;
      }
      goto jret0;
   }

   if(cmd == NULL)
      goto jret0;
   if((cmd->lc_argtype & ARG_P) && ok_blook(autoprint))
      if(visible(dot)){
         line.s = savestr("type");
         line.l = sizeof("type") -1;
         gp = (struct a_lex_ghost*)-1; /* Avoid `ghost' interpretation */
         goto jrestart;
      }

   if(!(pstate & (PS_SOURCING | PS_HOOK_MASK)) && !(cmd->lc_argtype & ARG_T))
      pstate |= PS_SAW_COMMAND;
jleave0:
   pstate &= ~PS_EVAL_ERROR;
jret0:
   e = 0;
jret:
/*
fprintf(stderr, "a_lex_evaluate returns %d for <%s>\n",e,line.s);
*/
   NYD_LEAVE;
   return e;
}

static struct a_lex_cmd const *
a_lex__firstfit(char const *comm){ /* TODO *hashtable*! linear list search!!! */
   struct a_lex_cmd const *cp;
   NYD2_ENTER;

   for(cp = a_lex_cmd_tab; PTRCMP(cp, <, &a_lex_cmd_tab[NELEM(a_lex_cmd_tab)]);
         ++cp)
      if(*comm == *cp->lc_name && is_prefix(comm, cp->lc_name))
         goto jleave;
   cp = NULL;
jleave:
   NYD2_LEAVE;
   return cp;
}

static void
a_lex_stop(int s){
   sighandler_type old_action;
   sigset_t nset;
   NYD_X; /* Signal handler */

   old_action = safe_signal(s, SIG_DFL);

   sigemptyset(&nset);
   sigaddset(&nset, s);
   sigprocmask(SIG_UNBLOCK, &nset, NULL);
   n_raise(s);
   sigprocmask(SIG_BLOCK, &nset, NULL);

   safe_signal(s, old_action);

   if(a_lex_reset_on_stop){
      a_lex_reset_on_stop = 0;
      n_TERMCAP_RESUME(TRU1);
      siglongjmp(srbuf, 0); /* FIXME get rid */
   }
}

static void
a_lex_hangup(int s){
   NYD_X; /* Signal handler */
   UNUSED(s);
   /* nothing to do? */
   exit(EXIT_ERR);
}

static void
a_lex_onintr(int s){
   NYD_X; /* Signal handler */

   safe_signal(SIGINT, a_lex_onintr);
   noreset = 0;
   a_lex_unstack(TRUM1);

   termios_state_reset();
   close_all_files(); /* FIXME .. to outer level ONLU! */

   if(image >= 0){
      close(image);
      image = -1;
   }
   if(interrupts != 1)
      n_err_sighdl(_("Interrupt\n"));
   safe_signal(SIGPIPE, a_lex_oldpipe);
   siglongjmp(srbuf, 0); /* FIXME get rid */
}

static void
a_lex_unstack(bool_t eval_error){
   struct a_lex_input_stack *lip;
   NYD_ENTER;

   if((lip = a_lex_input) == NULL){
      /* If called from a_lex_onintr(), be silent FIXME */
      pstate &= ~(PS_SOURCING | PS_ROBOT);
      if(eval_error == TRUM1 || !(pstate & PS_STARTED))
         goto jleave;
      goto jerr;
   }

   if(lip->li_flags & a_LEX_MACRO){
      if(lip->li_flags & a_LEX_MACRO_FREE_DATA){
         char **lp;

         while(*(lp = &lip->li_lines[lip->li_loff]) != NULL){
            free(*lp);
            ++lip->li_loff;
         }
         /* Part of lip's memory chunk, then */
         if(!(lip->li_flags & a_LEX_MACRO_CMD))
            free(lip->li_lines);
      }
   }else{
      if(lip->li_flags & a_LEX_PIPE)
         /* XXX command manager should -TERM then -KILL instead of hoping
          * XXX for exit of provider due to EPIPE / SIGPIPE */
         Pclose(lip->li_file, TRU1);
      else
         Fclose(lip->li_file);
   }

   if(!condstack_take(lip->li_cond)){
      n_err(_("Unmatched `if' at end of %s \"%s\"\n"),
         ((lip->li_flags & a_LEX_MACRO
          ? (lip->li_flags & a_LEX_MACRO_CMD ? _("command") : _("macro"))
          : _("`source'd file"))),
         lip->li_name);
      eval_error = TRU1;
   }

   if((a_lex_input = lip->li_outer) == NULL){
      pstate &= ~(PS_SOURCING | PS_ROBOT);
   }else{
      if((a_lex_input->li_flags & (a_LEX_MACRO | a_LEX_SUPER_MACRO)) ==
            (a_LEX_MACRO | a_LEX_SUPER_MACRO))
         pstate &= ~PS_SOURCING;
      assert(pstate & PS_ROBOT);
   }

   if(eval_error)
      goto jerr;
   if(lip->li_flags & a_LEX_FREE)
      free(lip);
jleave:
   if(UNLIKELY(a_lex_input != NULL && eval_error == TRUM1))
      a_lex_unstack(TRUM1);
   NYD_LEAVE;
   return;

jerr:
   if(lip != NULL){
      if(options & OPT_D_V)
         n_alert(_("Stopped %s \"%s\" due to errors%s"),
            (pstate & PS_STARTED
             ? (lip->li_flags & a_LEX_MACRO
                ? (lip->li_flags & a_LEX_MACRO_CMD
                   ? _("evaluating command") : _("evaluating macro"))
                : (lip->li_flags & a_LEX_PIPE
                   ? _("executing `source'd pipe")
                   : _("loading `source'd file")))
             : (lip->li_flags & a_LEX_MACRO
                ? (lip->li_flags & a_LEX_MACRO_X_OPTION
                   ? _("evaluating command line") : _("evaluating macro"))
                : _("loading initialization resource"))),
            lip->li_name,
            (options & OPT_DEBUG ? "" : _(" (enable *debug* for trace)")));
      if(lip->li_flags & a_LEX_FREE)
         free(lip);
   }

   if(!(options & OPT_INTERACTIVE) && !(pstate & PS_STARTED)){
      if(options & OPT_D_V)
         n_alert(_("Non-interactive, bailing out due to errors "
            "in startup load phase"));
      exit(EXIT_ERR);
   }
   goto jleave;
}

static bool_t
a_lex_source_file(char const *file, bool_t silent_error){
   struct a_lex_input_stack *lip;
   size_t nlen;
   char *nbuf;
   bool_t ispipe;
   FILE *fip;
   NYD_ENTER;

   fip = NULL;

   /* Being a command argument file is space-trimmed */
   if((ispipe = (!silent_error && (nlen = strlen(file)) > 0 &&
         file[--nlen] == '|'))){
      char const *sh;

      if((sh = ok_vlook(SHELL)) == NULL)
         sh = XSHELL;
      if((fip = Popen(nbuf = savestrbuf(file, nlen), "r",
            sh, NULL, COMMAND_FD_NULL)) == NULL){
         if(!silent_error || (options & OPT_D_V))
            n_perr(nbuf, 0);
         goto jleave;
      }
   }else if((nbuf = fexpand(file, FEXP_LOCAL)) == NULL)
      goto jleave;
   else if((fip = Fopen(nbuf, "r")) == NULL){
      if(!silent_error || (options & OPT_D_V))
         n_perr(nbuf, 0);
      goto jleave;
   }

   lip = smalloc(sizeof(*lip) -
         VFIELD_SIZEOF(struct a_lex_input_stack, li_name) +
         (nlen = strlen(nbuf) +1));
   lip->li_outer = a_lex_input;
   lip->li_file = fip;
   lip->li_cond = condstack_release();
   lip->li_flags = (ispipe ? a_LEX_PIPE : a_LEX_NONE) |
         (a_lex_input != NULL && (a_lex_input->li_flags & a_LEX_SUPER_MACRO)
          ? a_LEX_SUPER_MACRO : 0);
   memcpy(lip->li_name, nbuf, nlen);

   pstate |= PS_SOURCING | PS_ROBOT;
   a_lex_input = lip;
   a_commands_recursive();
/* FIXME return TRUM1 if file can't be opened, FAL0 on eval error */
jleave:
   NYD_LEAVE;
   return silent_error ? TRU1 : (fip != NULL);
}

static bool_t
a_lex_load(struct a_lex_input_stack *lip){
   bool_t rv;
   NYD2_ENTER;

   assert(!(pstate & PS_STARTED));
   assert(a_lex_input == NULL);

   /* POSIX:
    *    Any errors in the start-up file shall either cause mailx to terminate
    *    with a diagnostic message and a non-zero status or to continue after
    *    writing a diagnostic message, ignoring the remainder of the lines in
    *    the start-up file. */
   lip->li_cond = condstack_release();

/* FIXME won't work for now (PS_ROBOT needs PS_SOURCING anyway)
   pstate |= PS_ROBOT |
         (lip->li_flags & a_LEX_MACRO_X_OPTION ? 0 : PS_SOURCING);
*/
   pstate |= PS_ROBOT | PS_SOURCING;
   if(options & OPT_D_V)
      n_err(_("Loading \"%s\"\n"), lip->li_name);
   a_lex_input = lip;
   if(!(rv = n_commands())){
      if(!(options & OPT_INTERACTIVE)){
         if(options & OPT_D_V)
            n_alert(_("Non-interactive program mode, forced exit"));
         exit(EXIT_ERR);
      }
   }
   /* PS_EXIT handled by callers */
   NYD2_LEAVE;
   return rv;
}

static bool_t
a_commands_recursive(void){
   struct a_lex_eval_ctx ev;
   bool_t rv;
   NYD2_ENTER;

   memset(&ev, 0, sizeof ev);

/* FIXME sigkondom */
   n_COLOUR( n_colour_env_push(); )
   rv = TRU1;
   for(;;){
      int n;

      /* Read a line of commands and handle end of file specially */
      ev.le_line.l = ev.le_line_size;
      n = n_lex_input(NULL, TRU1, &ev.le_line.s, &ev.le_line.l,
            ev.le_new_content);
      ev.le_line_size = (ui32_t)ev.le_line.l;
      ev.le_line.l = (ui32_t)n;

      if(n < 0)
         break;

      if(a_lex_evaluate(&ev)){
         rv = FAL0;
         break;
      }

      if((options & OPT_BATCH_FLAG) && ok_blook(batch_exit_on_error)){
         if(exit_status != EXIT_OK)
            break;
      }
   }
   a_lex_unstack(!rv);
   n_COLOUR( n_colour_env_pop(FAL0); )

   if(ev.le_line.s != NULL)
      free(ev.le_line.s);
   NYD2_LEAVE;
   return rv;
}

#ifdef HAVE_DOCSTRINGS
FL bool_t
n_print_comm_docstr(char const *comm){
   struct a_lex_ghost const *gp;
   struct a_lex_cmd const *cp, *cpmax;
   bool_t rv = FAL0;
   NYD_ENTER;

   /* Ghosts take precedence */
   for(gp = a_lex_ghosts; gp != NULL; gp = gp->lg_next)
      if(!strcmp(comm, gp->lg_name)){
         printf("%s -> ", comm);
         comm = gp->lg_cmd.s;
         break;
      }

   cpmax = &(cp = a_lex_cmd_tab)[NELEM(a_lex_cmd_tab)];
jredo:
   for(; PTRCMP(cp, <, cpmax); ++cp){
      if(!strcmp(comm, cp->lc_name))
         printf("%s: %s\n", comm, V_(cp->lc_doc));
      else if(is_prefix(comm, cp->lc_name))
         printf("%s (%s): %s\n", comm, cp->lc_name, V_(cp->lc_doc));
      else
         continue;
      rv = TRU1;
      break;
   }
   if(!rv && PTRCMP(cpmax, ==, &a_lex_cmd_tab[NELEM(a_lex_cmd_tab)])){
      cpmax = &(cp = a_lex_special_cmd_tab)[NELEM(a_lex_special_cmd_tab)];
      goto jredo;
   }

   if(!rv && gp != NULL){
      printf("\"%s\"\n", comm);
      rv = TRU1;
   }
   NYD_LEAVE;
   return rv;
}
#endif /* HAVE_DOCSTRINGS */

FL bool_t
n_commands(void){ /* FIXME */
   struct a_lex_eval_ctx ev;
   int n;
   bool_t volatile rv = TRU1;
   NYD_ENTER;

   if (!(pstate & PS_SOURCING)) {
      if (safe_signal(SIGINT, SIG_IGN) != SIG_IGN)
         safe_signal(SIGINT, &a_lex_onintr);
      if (safe_signal(SIGHUP, SIG_IGN) != SIG_IGN)
         safe_signal(SIGHUP, &a_lex_hangup);
      /* TODO We do a lot of redundant signal handling, especially
       * TODO with the command line editor(s); try to merge this */
      safe_signal(SIGTSTP, &a_lex_stop);
      safe_signal(SIGTTOU, &a_lex_stop);
      safe_signal(SIGTTIN, &a_lex_stop);
   }
   a_lex_oldpipe = safe_signal(SIGPIPE, SIG_IGN);
   safe_signal(SIGPIPE, a_lex_oldpipe);

   memset(&ev, 0, sizeof ev);

   (void)sigsetjmp(srbuf, 1); /* FIXME get rid */
   for (;;) {
      char *temporary_orig_line; /* XXX eval_ctx.le_line not yet constant */

      n_COLOUR( n_colour_env_pop(TRU1); )

      /* TODO Unless we have our signal manager (or however we do it) child
       * TODO processes may have time slots where their execution isn't
       * TODO protected by signal handlers (in between start and setup
       * TODO completed).  close_all_files() is only called from onintr()
       * TODO so those may linger possibly forever */
      if(!(pstate & PS_SOURCING))
         close_all_files();

      interrupts = 0;

      temporary_localopts_free(); /* XXX intermediate hack */
      sreset((pstate & PS_SOURCING) != 0);
      if (!(pstate & PS_SOURCING)) {
         char *cp;

         /* TODO Note: this buffer may contain a password.  We should redefine
          * TODO the code flow which has to do that */
         if ((cp = termios_state.ts_linebuf) != NULL) {
            termios_state.ts_linebuf = NULL;
            termios_state.ts_linesize = 0;
            free(cp); /* TODO pool give-back */
         }
         /* TODO Due to expand-on-tab of NCL the buffer may grow */
         if (ev.le_line.l > LINESIZE * 3) {
            free(ev.le_line.s); /* TODO pool! but what? */
            ev.le_line.s = NULL;
            ev.le_line.l = ev.le_line_size = 0;
         }
      }

      if (!(pstate & PS_SOURCING) && (options & OPT_INTERACTIVE)) {
         char *cp;

         cp = ok_vlook(newmail);
         if ((options & OPT_TTYIN) && cp != NULL) {
            struct stat st;

/* FIXME TEST WITH NOPOLL ETC. !!! */
            n = (cp != NULL && strcmp(cp, "nopoll"));
            if ((mb.mb_type == MB_FILE && !stat(mailname, &st) &&
                     st.st_size > mailsize) ||
                  (mb.mb_type == MB_MAILDIR && n != 0)) {
               size_t odot = PTR2SIZE(dot - message);
               ui32_t odid = (pstate & PS_DID_PRINT_DOT);

               if (setfile(mailname,
                     FEDIT_NEWMAIL |
                     ((mb.mb_perm & MB_DELE) ? 0 : FEDIT_RDONLY)) < 0) {
                  exit_status |= EXIT_ERR;
                  rv = FAL0;
                  break;
               }
               dot = message + odot;
               pstate |= odid;
            }
         }

         a_lex_reset_on_stop = TRU1;
         exit_status = EXIT_OK;
      }

      /* Read a line of commands and handle end of file specially */
jreadline:
      ev.le_line.l = ev.le_line_size;
      n = n_lex_input(NULL, TRU1, &ev.le_line.s, &ev.le_line.l,
            ev.le_new_content);
      ev.le_line_size = (ui32_t)ev.le_line.l;
      ev.le_line.l = (ui32_t)n;
      a_lex_reset_on_stop = FAL0;

      if (n < 0) {
/* FIXME did unstack() when PS_SOURCING, only break with PS_LOADING*/
         if (!(pstate & PS_ROBOT) &&
               (options & OPT_INTERACTIVE) && ok_blook(ignoreeof)) {
            printf(_("*ignoreeof* set, use `quit' to quit.\n"));
            n_msleep(500, FAL0);
            continue;
         }
         break;
      }

      temporary_orig_line = ((pstate & PS_SOURCING) ||
         !(options & OPT_INTERACTIVE)) ? NULL
          : savestrbuf(ev.le_line.s, ev.le_line.l);
      pstate &= ~PS_HOOK_MASK;
      if (a_lex_evaluate(&ev)) {
         if (!(pstate & PS_STARTED)) /* TODO mess; join PS_EVAL_ERROR.. */
            rv = FAL0;
         break;
      }

      if ((options & OPT_BATCH_FLAG) && ok_blook(batch_exit_on_error)) {
         if (exit_status != EXIT_OK)
            break;
         if ((pstate & (PS_SOURCING | PS_EVAL_ERROR)) == PS_EVAL_ERROR) {
            exit_status = EXIT_ERR;
            break;
         }
      }
      if (!(pstate & PS_SOURCING) && (options & OPT_INTERACTIVE)) {
         if (ev.le_new_content != NULL)
            goto jreadline;
         /* *Can* happen since _evaluate() n_unstack()s on error! XXX no more */
         if (temporary_orig_line != NULL)
            n_tty_addhist(temporary_orig_line, !ev.le_add_history);
      }

      if(pstate & PS_EXIT)
         break;
   }
   a_lex_unstack(!rv);

   if (ev.le_line.s != NULL)
      free(ev.le_line.s);
   if (pstate & PS_SOURCING)
      sreset(FAL0);
   NYD_LEAVE;
   return rv;
}

FL int
(n_lex_input)(char const *prompt, bool_t nl_escape, char **linebuf,
      size_t *linesize, char const *string SMALLOC_DEBUG_ARGS){
   /* TODO readline: linebuf pool! */
   bool_t doprompt, dotty;
   int n, nold;
   FILE *ifile;
   NYD2_ENTER;

   /* Special case macro mode: never need to prompt, lines have always been
    * unfolded already */
   if(a_lex_input != NULL && (a_lex_input->li_flags & a_LEX_MACRO)){
      char **lp = &a_lex_input->li_lines[a_lex_input->li_loff];

      if(*linebuf != NULL)
         free(*linebuf);

      if((*linebuf = *lp) == NULL){
         *linesize = 0;
         n = -1;
      }else{
         ++a_lex_input->li_loff;
         n = (int)(*linesize = strlen(*linebuf));

         if(!(a_lex_input->li_flags & a_LEX_MACRO_FREE_DATA))
            *linebuf = sbufdup(*linebuf, *linesize);

         if(options & OPT_D_VV)
            n_err(_("%s %d bytes <%.*s>\n"),
               (a_lex_input->li_flags & a_LEX_MACRO_X_OPTION
                ? _("-X option") : _("MACRO")),
               n, n, *linebuf);
      }
      goto jleave;
   }

   doprompt = ((pstate & (PS_STARTED | PS_ROBOT)) == PS_STARTED &&
         (options & OPT_INTERACTIVE));
   dotty = (doprompt && !ok_blook(line_editor_disable));
   if(!doprompt)
      prompt = NULL;
   else if(prompt == NULL)
      prompt = getprompt();

   /* Ensure stdout is flushed first anyway */
   if(!dotty && prompt == NULL)
      fflush(stdout);

   ifile = (a_lex_input != NULL) ? a_lex_input->li_file : stdin;
   assert(ifile != NULL);

   for(nold = n = 0;;){
      if(dotty){
         assert(ifile == stdin);
         if(string != NULL && (n = (int)strlen(string)) > 0){
            if(*linesize > 0)
               *linesize += n +1;
            else
               *linesize = (size_t)n + LINESIZE +1;
            *linebuf = (srealloc)(*linebuf, *linesize SMALLOC_DEBUG_ARGSCALL);
           memcpy(*linebuf, string, (size_t)n +1);
         }
         string = NULL;
         /* TODO if nold>0, don't redisplay the entire line!
          * TODO needs complete redesign ... */
         n = (n_tty_readline)(prompt, linebuf, linesize, n
               SMALLOC_DEBUG_ARGSCALL);
      }else{
         if(prompt != NULL) {
            if(*prompt != '\0')
               fputs(prompt, stdout);
            fflush(stdout);
         }

         n = (readline_restart)(ifile, linebuf, linesize, n
               SMALLOC_DEBUG_ARGSCALL);

         if(n > 0 && nold > 0){
            int i = 0;
            char const *cp = *linebuf + nold;

            while(blankspacechar(*cp) && nold + i < n)
               ++cp, ++i;
            if(i > 0){
               memmove(*linebuf + nold, cp, n - nold - i);
               n -= i;
               (*linebuf)[n] = '\0';
            }
         }
      }

      if(n <= 0)
         break;

      /* POSIX says:
       *    An unquoted <backslash> at the end of a command line shall
       *    be discarded and the next line shall continue the command */
      if(!nl_escape || (*linebuf)[n - 1] != '\\')
         break;
      /* Definitely outside of quotes, thus the quoting rules are so that an
       * uneven number of successive backslashs at EOL is a continuation */
      if(n > 1){
         size_t i, j;

         for(j = 1, i = (size_t)n - 1; i-- > 0; ++j)
            if((*linebuf)[i] != '\\')
               break;
         if(!(j & 1))
            break;
      }
      (*linebuf)[nold = --n] = '\0';
      if(prompt != NULL && *prompt != '\0')
         prompt = ".. "; /* XXX PS2 .. */
   }

   if(n >= 0){
      (*linebuf)[*linesize = n] = '\0';

      if(options & OPT_D_VV)
         n_err(_("%s %d bytes <%.*s>\n"),
            (!(pstate & PS_STARTED) ? "LOAD"
             : (pstate & PS_SOURCING ? "SOURCE" : "READ")),
            n, n, *linebuf);
   }
jleave:
   NYD2_LEAVE;
   return n;
}

FL char *
n_lex_input_cp_addhist(char const *prompt, char const *string, bool_t isgabby){
   /* FIXME n_lex_input_cp_addhist(): leaks on sigjmp without linepool */
   size_t linesize;
   char *linebuf, *rv;
   int n;
   NYD2_ENTER;

   linesize = 0;
   linebuf = NULL;
   rv = NULL;

   n = n_lex_input(prompt, TRU1, &linebuf, &linesize, string);
   if(n > 0 && *(rv = savestrbuf(linebuf, (size_t)n)) != '\0' &&
         (options & OPT_INTERACTIVE))
      n_tty_addhist(rv, isgabby);

   if(linebuf != NULL)
      free(linebuf);
   NYD2_LEAVE;
   return rv;
}

FL void
n_load(char const *name){
   struct a_lex_input_stack *lip;
   size_t i;
   FILE *fip;
   NYD_ENTER;

   if(name == NULL || *name == '\0' || (fip = Fopen(name, "r")) == NULL)
      goto jleave;

   i = strlen(name) +1;
   lip = scalloc(1, sizeof(*lip) -
         VFIELD_SIZEOF(struct a_lex_input_stack, li_name) + i);
   lip->li_file = fip;
   lip->li_flags = a_LEX_FREE;
   memcpy(lip->li_name, name, i);

   a_lex_load(lip);
   pstate &= ~PS_EXIT;
jleave:
   NYD_LEAVE;
}

FL void
n_load_Xargs(char const **lines){
   static char const name[] = "-X";

   ui8_t buf[sizeof(struct a_lex_input_stack) + sizeof name];
   struct a_lex_input_stack *lip;
   NYD_ENTER;

   memset(buf, 0, sizeof buf);
   lip = (void*)buf;
   lip->li_flags = a_LEX_MACRO | a_LEX_MACRO_X_OPTION | a_LEX_SUPER_MACRO;
   lip->li_lines = UNCONST(lines);
   memcpy(lip->li_name, name, sizeof name);

   a_lex_load(lip);
   if(pstate & PS_EXIT)
      exit(EXIT_OK);
   NYD_LEAVE;
}

FL int
c_source(void *v){
   int rv;
   NYD_ENTER;

   rv = (a_lex_source_file(*(char**)v, FAL0) == TRU1) ? 0 : 1;
   NYD_LEAVE;
   return rv;
}

FL int
c_source_if(void *v){ /* XXX obsolete?, support file tests in `if' etc.! */
   int rv;
   NYD_ENTER;

   rv = (a_lex_source_file(*(char**)v, TRU1) != FAL0) ? 0 : 1;
   NYD_LEAVE;
   return rv;
}

FL bool_t
n_source_macro(char const *name, char **lines){
   struct a_lex_input_stack *lip;
   size_t i;
   int rv;
   NYD_ENTER;

   lip = smalloc(sizeof(*lip) -
         VFIELD_SIZEOF(struct a_lex_input_stack, li_name) +
         (i = strlen(name) +1));
   lip->li_outer = a_lex_input;
   lip->li_file = NULL;
   lip->li_cond = condstack_release();
   lip->li_flags = a_LEX_FREE | a_LEX_MACRO | a_LEX_MACRO_FREE_DATA |
         (a_lex_input == NULL || (a_lex_input->li_flags & a_LEX_SUPER_MACRO)
          ? a_LEX_SUPER_MACRO : 0);
   lip->li_loff = 0;
   lip->li_lines = lines;
   memcpy(lip->li_name, name, i);

   pstate |= PS_ROBOT;
   a_lex_input = lip;
   rv = a_commands_recursive();
   NYD_LEAVE;
   return rv;
}

FL bool_t
n_source_command(char const *cmd){
   struct a_lex_input_stack *lip;
   size_t i, ial;
   bool_t rv;
   NYD_ENTER;

   i = strlen(cmd);
   cmd = sbufdup(cmd, i++);
   ial = n_ALIGN(i);

   lip = smalloc(sizeof(*lip) -
         VFIELD_SIZEOF(struct a_lex_input_stack, li_name) +
         ial + 2*sizeof(char*));
   lip->li_outer = a_lex_input;
   lip->li_file = NULL;
   lip->li_cond = condstack_release();
   lip->li_flags = a_LEX_FREE | a_LEX_MACRO | a_LEX_MACRO_FREE_DATA |
         a_LEX_MACRO_CMD |
         (a_lex_input == NULL || (a_lex_input->li_flags & a_LEX_SUPER_MACRO)
          ? a_LEX_SUPER_MACRO : 0);
   lip->li_loff = 0;
   lip->li_lines = (void*)(lip->li_name + ial);
   lip->li_lines[0] = UNCONST(cmd); /* dup'ed above */
   lip->li_lines[1] = NULL;
   memcpy(lip->li_name, cmd, i);

   pstate |= PS_ROBOT;
   a_lex_input = lip;
   rv = a_commands_recursive();
   NYD_LEAVE;
   return rv;
}

FL bool_t
n_source_may_yield_control(void){
   return ((options & OPT_INTERACTIVE) &&
      (pstate & PS_STARTED) &&
      (!(pstate & PS_ROBOT) || (pstate & PS_RECURSED)) && /* Ok for ~: */
      (a_lex_input == NULL || a_lex_input->li_outer == NULL));
}

/* s-it-mode */