src/nvim/misc1.c

// This is an open source non-commercial project. Dear PVS-Studio, please check
// it. PVS-Studio Static Code Analyzer for C, C++ and C#: http://www.viva64.com

/*
 * misc1.c: functions that didn't seem to fit elsewhere
 */

#include <assert.h>
#include <inttypes.h>
#include <limits.h>
#include <stdbool.h>
#include <string.h>

#include "nvim/ascii.h"
#include "nvim/buffer.h"
#include "nvim/buffer_updates.h"
#include "nvim/charset.h"
#include "nvim/cursor.h"
#include "nvim/diff.h"
#include "nvim/edit.h"
#include "nvim/eval.h"
#include "nvim/event/stream.h"
#include "nvim/ex_cmds.h"
#include "nvim/ex_docmd.h"
#include "nvim/ex_getln.h"
#include "nvim/fileio.h"
#include "nvim/fold.h"
#include "nvim/func_attr.h"
#include "nvim/garray.h"
#include "nvim/getchar.h"
#include "nvim/indent.h"
#include "nvim/indent_c.h"
#include "nvim/main.h"
#include "nvim/mbyte.h"
#include "nvim/memline.h"
#include "nvim/memory.h"
#include "nvim/message.h"
#include "nvim/misc1.h"
#include "nvim/mouse.h"
#include "nvim/move.h"
#include "nvim/option.h"
#include "nvim/os/input.h"
#include "nvim/os/os.h"
#include "nvim/os/shell.h"
#include "nvim/os/signal.h"
#include "nvim/os/time.h"
#include "nvim/os_unix.h"
#include "nvim/quickfix.h"
#include "nvim/regexp.h"
#include "nvim/screen.h"
#include "nvim/search.h"
#include "nvim/state.h"
#include "nvim/strings.h"
#include "nvim/tag.h"
#include "nvim/ui.h"
#include "nvim/undo.h"
#include "nvim/vim.h"
#include "nvim/window.h"

#ifdef INCLUDE_GENERATED_DECLARATIONS
# include "misc1.c.generated.h"
#endif
// All user names (for ~user completion as done by shell).
static garray_T ga_users = GA_EMPTY_INIT_VALUE;

/*
 * get_leader_len() returns the length in bytes of the prefix of the given
 * string which introduces a comment.  If this string is not a comment then
 * 0 is returned.
 * When "flags" is not NULL, it is set to point to the flags of the recognized
 * comment leader.
 * "backward" must be true for the "O" command.
 * If "include_space" is set, include trailing whitespace while calculating the
 * length.
 */
int get_leader_len(char_u *line, char_u **flags, bool backward, bool include_space)
{
  int i, j;
  int result;
  int got_com = FALSE;
  int found_one;
  char_u part_buf[COM_MAX_LEN];         // buffer for one option part
  char_u *string;                  // pointer to comment string
  char_u *list;
  int middle_match_len = 0;
  char_u *prev_list;
  char_u *saved_flags = NULL;

  result = i = 0;
  while (ascii_iswhite(line[i])) {  // leading white space is ignored
    ++i;
  }

  /*
   * Repeat to match several nested comment strings.
   */
  while (line[i] != NUL) {
    /*
     * scan through the 'comments' option for a match
     */
    found_one = FALSE;
    for (list = curbuf->b_p_com; *list;) {
      // Get one option part into part_buf[].  Advance "list" to next
      // one.  Put "string" at start of string.
      if (!got_com && flags != NULL) {
        *flags = list;              // remember where flags started
      }
      prev_list = list;
      (void)copy_option_part(&list, part_buf, COM_MAX_LEN, ",");
      string = vim_strchr(part_buf, ':');
      if (string == NULL) {         // missing ':', ignore this part
        continue;
      }
      *string++ = NUL;              // isolate flags from string

      // If we found a middle match previously, use that match when this
      // is not a middle or end.
      if (middle_match_len != 0
          && vim_strchr(part_buf, COM_MIDDLE) == NULL
          && vim_strchr(part_buf, COM_END) == NULL) {
        break;
      }

      // When we already found a nested comment, only accept further
      // nested comments.
      if (got_com && vim_strchr(part_buf, COM_NEST) == NULL) {
        continue;
      }

      // When 'O' flag present and using "O" command skip this one.
      if (backward && vim_strchr(part_buf, COM_NOBACK) != NULL) {
        continue;
      }

      // Line contents and string must match.
      // When string starts with white space, must have some white space
      // (but the amount does not need to match, there might be a mix of
      // TABs and spaces).
      if (ascii_iswhite(string[0])) {
        if (i == 0 || !ascii_iswhite(line[i - 1])) {
          continue;            // missing white space
        }
        while (ascii_iswhite(string[0])) {
          ++string;
        }
      }
      for (j = 0; string[j] != NUL && string[j] == line[i + j]; ++j) {
      }
      if (string[j] != NUL) {
        continue;          // string doesn't match
      }
      // When 'b' flag used, there must be white space or an
      // end-of-line after the string in the line.
      if (vim_strchr(part_buf, COM_BLANK) != NULL
          && !ascii_iswhite(line[i + j]) && line[i + j] != NUL) {
        continue;
      }

      // We have found a match, stop searching unless this is a middle
      // comment. The middle comment can be a substring of the end
      // comment in which case it's better to return the length of the
      // end comment and its flags.  Thus we keep searching with middle
      // and end matches and use an end match if it matches better.
      if (vim_strchr(part_buf, COM_MIDDLE) != NULL) {
        if (middle_match_len == 0) {
          middle_match_len = j;
          saved_flags = prev_list;
        }
        continue;
      }
      if (middle_match_len != 0 && j > middle_match_len) {
        // Use this match instead of the middle match, since it's a
        // longer thus better match.
        middle_match_len = 0;
      }

      if (middle_match_len == 0) {
        i += j;
      }
      found_one = TRUE;
      break;
    }

    if (middle_match_len != 0) {
      // Use the previously found middle match after failing to find a
      // match with an end.
      if (!got_com && flags != NULL) {
        *flags = saved_flags;
      }
      i += middle_match_len;
      found_one = TRUE;
    }

    // No match found, stop scanning.
    if (!found_one) {
      break;
    }

    result = i;

    // Include any trailing white space.
    while (ascii_iswhite(line[i])) {
      ++i;
    }

    if (include_space) {
      result = i;
    }

    // If this comment doesn't nest, stop here.
    got_com = TRUE;
    if (vim_strchr(part_buf, COM_NEST) == NULL) {
      break;
    }
  }
  return result;
}

/*
 * Return the offset at which the last comment in line starts. If there is no
 * comment in the whole line, -1 is returned.
 *
 * When "flags" is not null, it is set to point to the flags describing the
 * recognized comment leader.
 */
int get_last_leader_offset(char_u *line, char_u **flags)
{
  int result = -1;
  int i, j;
  int lower_check_bound = 0;
  char_u *string;
  char_u *com_leader;
  char_u *com_flags;
  char_u *list;
  int found_one;
  char_u part_buf[COM_MAX_LEN];         // buffer for one option part

  /*
   * Repeat to match several nested comment strings.
   */
  i = (int)STRLEN(line);
  while (--i >= lower_check_bound) {
    /*
     * scan through the 'comments' option for a match
     */
    found_one = FALSE;
    for (list = curbuf->b_p_com; *list;) {
      char_u *flags_save = list;

      /*
       * Get one option part into part_buf[].  Advance list to next one.
       * put string at start of string.
       */
      (void)copy_option_part(&list, part_buf, COM_MAX_LEN, ",");
      string = vim_strchr(part_buf, ':');
      if (string == NULL) {  // If everything is fine, this cannot actually
                             // happen.
        continue;
      }
      *string++ = NUL;          // Isolate flags from string.
      com_leader = string;

      /*
       * Line contents and string must match.
       * When string starts with white space, must have some white space
       * (but the amount does not need to match, there might be a mix of
       * TABs and spaces).
       */
      if (ascii_iswhite(string[0])) {
        if (i == 0 || !ascii_iswhite(line[i - 1])) {
          continue;
        }
        while (ascii_iswhite(*string)) {
          string++;
        }
      }
      for (j = 0; string[j] != NUL && string[j] == line[i + j]; ++j) {
        // do nothing
      }
      if (string[j] != NUL) {
        continue;
      }

      /*
       * When 'b' flag used, there must be white space or an
       * end-of-line after the string in the line.
       */
      if (vim_strchr(part_buf, COM_BLANK) != NULL
          && !ascii_iswhite(line[i + j]) && line[i + j] != NUL) {
        continue;
      }

      if (vim_strchr(part_buf, COM_MIDDLE) != NULL) {
        // For a middlepart comment, only consider it to match if
        // everything before the current position in the line is
        // whitespace.  Otherwise we would think we are inside a
        // comment if the middle part appears somewhere in the middle
        // of the line.  E.g. for C the "*" appears often.
        for (j = 0; j <= i && ascii_iswhite(line[j]); j++) {
        }
        if (j < i) {
          continue;
        }
      }

      /*
       * We have found a match, stop searching.
       */
      found_one = TRUE;

      if (flags) {
        *flags = flags_save;
      }
      com_flags = flags_save;

      break;
    }

    if (found_one) {
      char_u part_buf2[COM_MAX_LEN];            // buffer for one option part
      int len1, len2, off;

      result = i;
      /*
       * If this comment nests, continue searching.
       */
      if (vim_strchr(part_buf, COM_NEST) != NULL) {
        continue;
      }

      lower_check_bound = i;

      // Let's verify whether the comment leader found is a substring
      // of other comment leaders. If it is, let's adjust the
      // lower_check_bound so that we make sure that we have determined
      // the comment leader correctly.

      while (ascii_iswhite(*com_leader)) {
        ++com_leader;
      }
      len1 = (int)STRLEN(com_leader);

      for (list = curbuf->b_p_com; *list;) {
        char_u *flags_save = list;

        (void)copy_option_part(&list, part_buf2, COM_MAX_LEN, ",");
        if (flags_save == com_flags) {
          continue;
        }
        string = vim_strchr(part_buf2, ':');
        ++string;
        while (ascii_iswhite(*string)) {
          ++string;
        }
        len2 = (int)STRLEN(string);
        if (len2 == 0) {
          continue;
        }

        // Now we have to verify whether string ends with a substring
        // beginning the com_leader.
        for (off = (len2 > i ? i : len2); off > 0 && off + len1 > len2;) {
          --off;
          if (!STRNCMP(string + off, com_leader, len2 - off)) {
            if (i - off < lower_check_bound) {
              lower_check_bound = i - off;
            }
          }
        }
      }
    }
  }
  return result;
}

int gchar_pos(pos_T *pos)
  FUNC_ATTR_NONNULL_ARG(1)
{
  // When searching columns is sometimes put at the end of a line.
  if (pos->col == MAXCOL) {
    return NUL;
  }
  return utf_ptr2char(ml_get_pos(pos));
}

/*
 * check_status: called when the status bars for the buffer 'buf'
 *               need to be updated
 */
void check_status(buf_T *buf)
{
  FOR_ALL_WINDOWS_IN_TAB(wp, curtab) {
    if (wp->w_buffer == buf && wp->w_status_height) {
      wp->w_redr_status = TRUE;
      if (must_redraw < VALID) {
        must_redraw = VALID;
      }
    }
  }
}

/// Ask for a reply from the user, 'y' or 'n'
///
/// No other characters are accepted, the message is repeated until a valid
/// reply is entered or <C-c> is hit.
///
/// @param[in]  str  Prompt: question to ask user. Is always followed by
///                  " (y/n)?".
/// @param[in]  direct  Determines what function to use to get user input. If
///                     true then ui_inchar() will be used, otherwise vgetc().
///                     I.e. when direct is true then characters are obtained
///                     directly from the user without buffers involved.
///
/// @return 'y' or 'n'. Last is also what will be returned in case of interrupt.
int ask_yesno(const char *const str, const bool direct)
{
  const int save_State = State;

  no_wait_return++;
  State = CONFIRM;  // Mouse behaves like with :confirm.
  setmouse();  // Disable mouse in xterm.
  no_mapping++;

  int r = ' ';
  while (r != 'y' && r != 'n') {
    // Same highlighting as for wait_return.
    smsg_attr(HL_ATTR(HLF_R), "%s (y/n)?", str);
    if (direct) {
      r = get_keystroke(NULL);
    } else {
      r = plain_vgetc();
    }
    if (r == Ctrl_C || r == ESC) {
      r = 'n';
    }
    msg_putchar(r);  // Show what you typed.
    ui_flush();
  }
  no_wait_return--;
  State = save_State;
  setmouse();
  no_mapping--;

  return r;
}

/*
 * Return TRUE if "c" is a mouse key.
 */
int is_mouse_key(int c)
{
  return c == K_LEFTMOUSE
         || c == K_LEFTMOUSE_NM
         || c == K_LEFTDRAG
         || c == K_LEFTRELEASE
         || c == K_LEFTRELEASE_NM
         || c == K_MOUSEMOVE
         || c == K_MIDDLEMOUSE
         || c == K_MIDDLEDRAG
         || c == K_MIDDLERELEASE
         || c == K_RIGHTMOUSE
         || c == K_RIGHTDRAG
         || c == K_RIGHTRELEASE
         || c == K_MOUSEDOWN
         || c == K_MOUSEUP
         || c == K_MOUSELEFT
         || c == K_MOUSERIGHT
         || c == K_X1MOUSE
         || c == K_X1DRAG
         || c == K_X1RELEASE
         || c == K_X2MOUSE
         || c == K_X2DRAG
         || c == K_X2RELEASE;
}

/*
 * Get a key stroke directly from the user.
 * Ignores mouse clicks and scrollbar events, except a click for the left
 * button (used at the more prompt).
 * Doesn't use vgetc(), because it syncs undo and eats mapped characters.
 * Disadvantage: typeahead is ignored.
 * Translates the interrupt character for unix to ESC.
 */
int get_keystroke(MultiQueue *events)
{
  char_u *buf = NULL;
  int buflen = 150;
  int maxlen;
  int len = 0;
  int n;
  int save_mapped_ctrl_c = mapped_ctrl_c;
  int waited = 0;

  mapped_ctrl_c = 0;        // mappings are not used here
  for (;;) {
    // flush output before waiting
    ui_flush();
    // Leave some room for check_termcode() to insert a key code into (max
    // 5 chars plus NUL).  And fix_input_buffer() can triple the number of
    // bytes.
    maxlen = (buflen - 6 - len) / 3;
    if (buf == NULL) {
      buf = xmalloc((size_t)buflen);
    } else if (maxlen < 10) {
      // Need some more space. This might happen when receiving a long
      // escape sequence.
      buflen += 100;
      buf = xrealloc(buf, (size_t)buflen);
      maxlen = (buflen - 6 - len) / 3;
    }

    // First time: blocking wait.  Second time: wait up to 100ms for a
    // terminal code to complete.
    n = os_inchar(buf + len, maxlen, len == 0 ? -1L : 100L, 0, events);
    if (n > 0) {
      // Replace zero and CSI by a special key code.
      n = fix_input_buffer(buf + len, n);
      len += n;
      waited = 0;
    } else if (len > 0) {
      ++waited;             // keep track of the waiting time
    }
    if (n > 0) {  // found a termcode: adjust length
      len = n;
    }
    if (len == 0) {  // nothing typed yet
      continue;
    }

    // Handle modifier and/or special key code.
    n = buf[0];
    if (n == K_SPECIAL) {
      n = TO_SPECIAL(buf[1], buf[2]);
      if (buf[1] == KS_MODIFIER
          || n == K_IGNORE
          || (is_mouse_key(n) && n != K_LEFTMOUSE)) {
        if (buf[1] == KS_MODIFIER) {
          mod_mask = buf[2];
        }
        len -= 3;
        if (len > 0) {
          memmove(buf, buf + 3, (size_t)len);
        }
        continue;
      }
      break;
    }
    if (MB_BYTE2LEN(n) > len) {
      // more bytes to get.
      continue;
    }
    buf[len >= buflen ? buflen - 1 : len] = NUL;
    n = utf_ptr2char(buf);
    break;
  }
  xfree(buf);

  mapped_ctrl_c = save_mapped_ctrl_c;
  return n;
}

/// Get a number from the user.
/// When "mouse_used" is not NULL allow using the mouse.
///
/// @param colon  allow colon to abort
int get_number(int colon, int *mouse_used)
{
  int n = 0;
  int c;
  int typed = 0;

  if (mouse_used != NULL) {
    *mouse_used = FALSE;
  }

  // When not printing messages, the user won't know what to type, return a
  // zero (as if CR was hit).
  if (msg_silent != 0) {
    return 0;
  }

  no_mapping++;
  for (;;) {
    ui_cursor_goto(msg_row, msg_col);
    c = safe_vgetc();
    if (ascii_isdigit(c)) {
      n = n * 10 + c - '0';
      msg_putchar(c);
      ++typed;
    } else if (c == K_DEL || c == K_KDEL || c == K_BS || c == Ctrl_H) {
      if (typed > 0) {
        msg_puts("\b \b");
        --typed;
      }
      n /= 10;
    } else if (mouse_used != NULL && c == K_LEFTMOUSE) {
      *mouse_used = TRUE;
      n = mouse_row + 1;
      break;
    } else if (n == 0 && c == ':' && colon) {
      stuffcharReadbuff(':');
      if (!exmode_active) {
        cmdline_row = msg_row;
      }
      skip_redraw = true;           // skip redraw once
      do_redraw = false;
      break;
    } else if (c == Ctrl_C || c == ESC || c == 'q') {
      n = 0;
      break;
    } else if (c == CAR || c == NL) {
      break;
    }
  }
  no_mapping--;
  return n;
}

/*
 * Ask the user to enter a number.
 * When "mouse_used" is not NULL allow using the mouse and in that case return
 * the line number.
 */
int prompt_for_number(int *mouse_used)
{
  int i;
  int save_cmdline_row;
  int save_State;

  // When using ":silent" assume that <CR> was entered.
  if (mouse_used != NULL) {
    msg_puts(_("Type number and <Enter> or click with the mouse "
               "(q or empty cancels): "));
  } else {
    msg_puts(_("Type number and <Enter> (q or empty cancels): "));
  }

  /* Set the state such that text can be selected/copied/pasted and we still
   * get mouse events. */
  save_cmdline_row = cmdline_row;
  cmdline_row = 0;
  save_State = State;
  State = ASKMORE;  // prevents a screen update when using a timer
  // May show different mouse shape.
  setmouse();

  i = get_number(TRUE, mouse_used);
  if (KeyTyped) {
    // don't call wait_return() now
    if (msg_row > 0) {
      cmdline_row = msg_row - 1;
    }
    need_wait_return = false;
    msg_didany = false;
    msg_didout = false;
  } else {
    cmdline_row = save_cmdline_row;
  }
  State = save_State;
  // May need to restore mouse shape.
  setmouse();

  return i;
}

void msgmore(long n)
{
  long pn;

  if (global_busy           // no messages now, wait until global is finished
      || !messaging()) {      // 'lazyredraw' set, don't do messages now
    return;
  }

  // We don't want to overwrite another important message, but do overwrite
  // a previous "more lines" or "fewer lines" message, so that "5dd" and
  // then "put" reports the last action.
  if (keep_msg != NULL && !keep_msg_more) {
    return;
  }

  if (n > 0) {
    pn = n;
  } else {
    pn = -n;
  }

  if (pn > p_report) {
    if (n > 0) {
      vim_snprintf(msg_buf, MSG_BUF_LEN,
                   NGETTEXT("%ld more line", "%ld more lines", pn),
                   pn);
    } else {
      vim_snprintf(msg_buf, MSG_BUF_LEN,
                   NGETTEXT("%ld line less", "%ld fewer lines", pn),
                   pn);
    }
    if (got_int) {
      xstrlcat(msg_buf, _(" (Interrupted)"), MSG_BUF_LEN);
    }
    if (msg(msg_buf)) {
      set_keep_msg(msg_buf, 0);
      keep_msg_more = true;
    }
  }
}

/*
 * flush map and typeahead buffers and give a warning for an error
 */
void beep_flush(void)
{
  if (emsg_silent == 0) {
    flush_buffers(FLUSH_MINIMAL);
    vim_beep(BO_ERROR);
  }
}

// Give a warning for an error
// val is one of the BO_ values, e.g., BO_OPER
void vim_beep(unsigned val)
{
  called_vim_beep = true;

  if (emsg_silent == 0) {
    if (!((bo_flags & val) || (bo_flags & BO_ALL))) {
      static int beeps = 0;
      static uint64_t start_time = 0;

      // Only beep up to three times per half a second,
      // otherwise a sequence of beeps would freeze Vim.
      if (start_time == 0 || os_hrtime() - start_time > 500000000u) {
        beeps = 0;
        start_time = os_hrtime();
      }
      beeps++;
      if (beeps <= 3) {
        if (p_vb) {
          ui_call_visual_bell();
        } else {
          ui_call_bell();
        }
      }
    }

    // When 'debug' contains "beep" produce a message.  If we are sourcing
    // a script or executing a function give the user a hint where the beep
    // comes from.
    if (vim_strchr(p_debug, 'e') != NULL) {
      msg_source(HL_ATTR(HLF_W));
      msg_attr(_("Beep!"), HL_ATTR(HLF_W));
    }
  }
}

#if defined(EXITFREE)

void free_users(void)
{
  ga_clear_strings(&ga_users);
}

#endif

/*
 * Find all user names for user completion.
 * Done only once and then cached.
 */
static void init_users(void)
{
  static int lazy_init_done = FALSE;

  if (lazy_init_done) {
    return;
  }

  lazy_init_done = TRUE;

  os_get_usernames(&ga_users);
}

/*
 * Function given to ExpandGeneric() to obtain an user names.
 */
char_u *get_users(expand_T *xp, int idx)
{
  init_users();
  if (idx < ga_users.ga_len) {
    return ((char_u **)ga_users.ga_data)[idx];
  }
  return NULL;
}

/*
 * Check whether name matches a user name. Return:
 * 0 if name does not match any user name.
 * 1 if name partially matches the beginning of a user name.
 * 2 is name fully matches a user name.
 */
int match_user(char_u *name)
{
  int n = (int)STRLEN(name);
  int result = 0;

  init_users();
  for (int i = 0; i < ga_users.ga_len; i++) {
    if (STRCMP(((char_u **)ga_users.ga_data)[i], name) == 0) {
      return 2;       // full match
    }
    if (STRNCMP(((char_u **)ga_users.ga_data)[i], name, n) == 0) {
      result = 1;       // partial match
    }
  }
  return result;
}

/// Preserve files and exit.
/// @note IObuff must contain a message.
/// @note This may be called from deadly_signal() in a signal handler, avoid
///       unsafe functions, such as allocating memory.
void preserve_exit(void)
  FUNC_ATTR_NORETURN
{
  // 'true' when we are sure to exit, e.g., after a deadly signal
  static bool really_exiting = false;

  // Prevent repeated calls into this method.
  if (really_exiting) {
    if (input_global_fd() >= 0) {
      // normalize stream (#2598)
      stream_set_blocking(input_global_fd(), true);
    }
    exit(2);
  }

  really_exiting = true;
  // Ignore SIGHUP while we are already exiting. #9274
  signal_reject_deadly();
  mch_errmsg(IObuff);
  mch_errmsg("\n");
  ui_flush();

  ml_close_notmod();                // close all not-modified buffers

  FOR_ALL_BUFFERS(buf) {
    if (buf->b_ml.ml_mfp != NULL && buf->b_ml.ml_mfp->mf_fname != NULL) {
      mch_errmsg("Vim: preserving files...\r\n");
      ui_flush();
      ml_sync_all(false, false, true);  // preserve all swap files
      break;
    }
  }

  ml_close_all(false);              // close all memfiles, without deleting

  mch_errmsg("Vim: Finished.\r\n");

  getout(1);
}

/*
 * Check for CTRL-C pressed, but only once in a while.
 * Should be used instead of os_breakcheck() for functions that check for
 * each line in the file.  Calling os_breakcheck() each time takes too much
 * time, because it can be a system call.
 */

#ifndef BREAKCHECK_SKIP
# define BREAKCHECK_SKIP 1000
#endif

static int breakcheck_count = 0;

void line_breakcheck(void)
{
  if (++breakcheck_count >= BREAKCHECK_SKIP) {
    breakcheck_count = 0;
    os_breakcheck();
  }
}

/*
 * Like line_breakcheck() but check 10 times less often.
 */
void fast_breakcheck(void)
{
  if (++breakcheck_count >= BREAKCHECK_SKIP * 10) {
    breakcheck_count = 0;
    os_breakcheck();
  }
}

// Like line_breakcheck() but check 100 times less often.
void veryfast_breakcheck(void)
{
  if (++breakcheck_count >= BREAKCHECK_SKIP * 100) {
    breakcheck_count = 0;
    os_breakcheck();
  }
}

/// os_call_shell() wrapper. Handles 'verbose', :profile, and v:shell_error.
/// Invalidates cached tags.
///
/// @return shell command exit code
int call_shell(char_u *cmd, ShellOpts opts, char_u *extra_shell_arg)
{
  int retval;
  proftime_T wait_time;

  if (p_verbose > 3) {
    verbose_enter();
    smsg(_("Executing command: \"%s\""), cmd == NULL ? p_sh : cmd);
    msg_putchar('\n');
    verbose_leave();
  }

  if (do_profiling == PROF_YES) {
    prof_child_enter(&wait_time);
  }

  if (*p_sh == NUL) {
    emsg(_(e_shellempty));
    retval = -1;
  } else {
    // The external command may update a tags file, clear cached tags.
    tag_freematch();

    retval = os_call_shell(cmd, opts, extra_shell_arg);
  }

  set_vim_var_nr(VV_SHELL_ERROR, (varnumber_T)retval);
  if (do_profiling == PROF_YES) {
    prof_child_exit(&wait_time);
  }

  return retval;
}

/// Get the stdout of an external command.
/// If "ret_len" is NULL replace NUL characters with NL. When "ret_len" is not
/// NULL store the length there.
///
/// @param  cmd      command to execute
/// @param  infile   optional input file name
/// @param  flags    can be kShellOptSilent or 0
/// @param  ret_len  length of the stdout
///
/// @return an allocated string, or NULL for error.
char_u *get_cmd_output(char_u *cmd, char_u *infile, ShellOpts flags, size_t *ret_len)
{
  char_u *buffer = NULL;

  if (check_secure()) {
    return NULL;
  }

  // get a name for the temp file
  char_u *tempname = vim_tempname();
  if (tempname == NULL) {
    emsg(_(e_notmp));
    return NULL;
  }

  // Add the redirection stuff
  char_u *command = make_filter_cmd(cmd, infile, tempname);

  /*
   * Call the shell to execute the command (errors are ignored).
   * Don't check timestamps here.
   */
  ++no_check_timestamps;
  call_shell(command, kShellOptDoOut | kShellOptExpand | flags, NULL);
  --no_check_timestamps;

  xfree(command);

  // read the names from the file into memory
  FILE *fd = os_fopen((char *)tempname, READBIN);

  if (fd == NULL) {
    semsg(_(e_notopen), tempname);
    goto done;
  }

  fseek(fd, 0L, SEEK_END);
  size_t len = (size_t)ftell(fd);  // get size of temp file
  fseek(fd, 0L, SEEK_SET);

  buffer = xmalloc(len + 1);
  size_t i = fread((char *)buffer, 1, len, fd);
  fclose(fd);
  os_remove((char *)tempname);
  if (i != len) {
    semsg(_(e_notread), tempname);
    XFREE_CLEAR(buffer);
  } else if (ret_len == NULL) {
    // Change NUL into SOH, otherwise the string is truncated.
    for (i = 0; i < len; ++i) {
      if (buffer[i] == NUL) {
        buffer[i] = 1;
      }
    }

    buffer[len] = NUL;          // make sure the buffer is terminated
  } else {
    *ret_len = len;
  }

done:
  xfree(tempname);
  return buffer;
}

/*
 * Free the list of files returned by expand_wildcards() or other expansion
 * functions.
 */
void FreeWild(int count, char_u **files)
{
  if (count <= 0 || files == NULL) {
    return;
  }
  while (count--) {
    xfree(files[count]);
  }
  xfree(files);
}

/*
 * Return TRUE when need to go to Insert mode because of 'insertmode'.
 * Don't do this when still processing a command or a mapping.
 * Don't do this when inside a ":normal" command.
 */
int goto_im(void)
{
  return p_im && stuff_empty() && typebuf_typed();
}

/// Put the timestamp of an undo header in "buf[buflen]" in a nice format.
void add_time(char_u *buf, size_t buflen, time_t tt)
{
  struct tm curtime;

  if (time(NULL) - tt >= 100) {
    os_localtime_r(&tt, &curtime);
    if (time(NULL) - tt < (60L * 60L * 12L)) {
      // within 12 hours
      (void)strftime((char *)buf, buflen, "%H:%M:%S", &curtime);
    } else {
      // longer ago
      (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", &curtime);
    }
  } else {
    int64_t seconds = time(NULL) - tt;
    vim_snprintf((char *)buf, buflen,
                 NGETTEXT("%" PRId64 " second ago",
                          "%" PRId64 " seconds ago", (uint32_t)seconds),
                 seconds);
  }
}