Merge #850 'impl mkdtemp for windows, refactor vim_tempname'

25 files changed, 288 insertions, 239 deletions

diff --git a/clint-files.txt b/clint-files.txt
index da0643e834..29fb0908af 100644
--- a/clint-files.txt
+++ b/clint-files.txt
@@ -48,3 +48,5 @@ src/nvim/os/server.c
 src/nvim/os/server.h
 src/nvim/os/channel.c
 src/nvim/os/channel.h
+src/nvim/tempfile.c
+src/nvim/tempfile.h
diff --git a/config/config.h.in b/config/config.h.in
index 05644d6274..628d128512 100644
--- a/config/config.h.in
+++ b/config/config.h.in
@@ -41,7 +41,6 @@
 #define HAVE_LIBINTL_H 1
 #define HAVE_LOCALE_H 1
 #define HAVE_LSTAT 1
-#define HAVE_MKDTEMP 1
 #define HAVE_NANOSLEEP 1
 #define HAVE_NL_LANGINFO_CODESET 1
 #define HAVE_NL_MSG_CAT_CNTR 1
diff --git a/src/nvim/CMakeLists.txt b/src/nvim/CMakeLists.txt
index 6b0538c52d..4a23e76a1c 100644
--- a/src/nvim/CMakeLists.txt
+++ b/src/nvim/CMakeLists.txt
@@ -55,6 +55,7 @@ set(CONV_SRCS
   os/uv_helpers.c
   os/wstream.c
   os/msgpack_rpc.c
+  tempfile.c
   api/buffer.c
   api/private/helpers.c
   api/private/handle.c
diff --git a/src/nvim/diff.c b/src/nvim/diff.c
index e7feacd4fb..ab0c80112f 100644
--- a/src/nvim/diff.c
+++ b/src/nvim/diff.c
@@ -30,6 +30,7 @@
 #include "nvim/path.h"
 #include "nvim/screen.h"
 #include "nvim/strings.h"
+#include "nvim/tempfile.h"
 #include "nvim/undo.h"
 #include "nvim/window.h"
 #include "nvim/os/os.h"
@@ -661,9 +662,9 @@ void ex_diffupdate(exarg_T *eap)
   }
 
   // We need three temp file names.
-  char_u *tmp_orig = vim_tempname('o');
-  char_u *tmp_new = vim_tempname('n');
-  char_u *tmp_diff = vim_tempname('d');
+  char_u *tmp_orig = vim_tempname();
+  char_u *tmp_new = vim_tempname();
+  char_u *tmp_diff = vim_tempname();
 
   if ((tmp_orig == NULL) || (tmp_new == NULL) || (tmp_diff == NULL)) {
     goto theend;
@@ -852,9 +853,9 @@ void ex_diffpatch(exarg_T *eap)
 #endif  // ifdef UNIX
   // We need two temp file names.
   // Name of original temp file.
-  char_u *tmp_orig = vim_tempname('o');
+  char_u *tmp_orig = vim_tempname();
   // Name of patched temp file.
-  char_u *tmp_new = vim_tempname('n');
+  char_u *tmp_new = vim_tempname();
 
   if ((tmp_orig == NULL) || (tmp_new == NULL)) {
     goto theend;
@@ -893,15 +894,11 @@ void ex_diffpatch(exarg_T *eap)
       || (os_chdir((char *)dirbuf) != 0)) {
     dirbuf[0] = NUL;
   } else {
-# ifdef TEMPDIRNAMES
-    if (vim_tempdir != NULL) {
-      ignored = os_chdir((char *)vim_tempdir);
-    } else {
-      ignored = os_chdir("/tmp");
+    char *tempdir = (char *)vim_gettempdir();
+    if (tempdir == NULL) {
+      tempdir = "/tmp";
     }
-# else
-    ignored = os_chdir("/tmp");
-# endif  // ifdef TEMPDIRNAMES
+    os_chdir(tempdir);
     shorten_fnames(TRUE);
   }
 #endif  // ifdef UNIX
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index eafdd2446c..3459b5c4a0 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -68,6 +68,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/tag.h"
+#include "nvim/tempfile.h"
 #include "nvim/term.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
@@ -14030,7 +14031,7 @@ static void f_system(typval_T *argvars, typval_T *rettv)
      * Write the string to a temp file, to be used for input of the shell
      * command.
      */
-    if ((infile = vim_tempname('i')) == NULL) {
+    if ((infile = vim_tempname()) == NULL) {
       EMSG(_(e_notmp));
       goto done;
     }
@@ -14231,22 +14232,8 @@ static void f_taglist(typval_T *argvars, typval_T *rettv)
  */
 static void f_tempname(typval_T *argvars, typval_T *rettv)
 {
-  static int x = 'A';
-
   rettv->v_type = VAR_STRING;
-  rettv->vval.v_string = vim_tempname(x);
-
-  /* Advance 'x' to use A-Z and 0-9, so that there are at least 34 different
-   * names.  Skip 'I' and 'O', they are used for shell redirection. */
-  do {
-    if (x == 'Z')
-      x = '0';
-    else if (x == '9')
-      x = 'A';
-    else {
-      ++x;
-    }
-  } while (x == 'I' || x == 'O');
+  rettv->vval.v_string = vim_tempname();
 }
 
 /*
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index 78325fd4a4..384eebe556 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -59,6 +59,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/tag.h"
+#include "nvim/tempfile.h"
 #include "nvim/term.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
@@ -1032,8 +1033,8 @@ do_filter (
     curbuf->b_op_start.lnum = line1;
     curbuf->b_op_end.lnum = line2;
     curwin->w_cursor.lnum = line2;
-  } else if ((do_in && (itmp = vim_tempname('i')) == NULL)
-      || (do_out && (otmp = vim_tempname('o')) == NULL)) {
+  } else if ((do_in && (itmp = vim_tempname()) == NULL)
+      || (do_out && (otmp = vim_tempname()) == NULL)) {
     EMSG(_(e_notmp));
     goto filterend;
   }
@@ -1601,7 +1602,7 @@ void write_viminfo(char_u *file, int forceit)
        */
       if (fp_out == NULL) {
         free(tempname);
-        if ((tempname = vim_tempname('o')) != NULL)
+        if ((tempname = vim_tempname()) != NULL)
           fp_out = mch_fopen((char *)tempname, WRITEBIN);
       }
 
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index ea32e19b50..c867211a66 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -49,6 +49,7 @@
 #include "nvim/search.h"
 #include "nvim/sha256.h"
 #include "nvim/strings.h"
+#include "nvim/tempfile.h"
 #include "nvim/term.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
@@ -2146,7 +2147,7 @@ readfile_charconvert (
   char_u      *tmpname;
   char_u      *errmsg = NULL;
 
-  tmpname = vim_tempname('r');
+  tmpname = vim_tempname();
   if (tmpname == NULL)
     errmsg = (char_u *)_("Can't find temp file for conversion");
   else {
@@ -3163,7 +3164,7 @@ nobackup:
      * overwrite the original file.
      */
     if (*p_ccv != NUL) {
-      wfname = vim_tempname('w');
+      wfname = vim_tempname();
       if (wfname == NULL) {             /* Can't write without a tempfile! */
         errmsg = (char_u *)_("E214: Can't find temp file for writing");
         goto restore_backup;
@@ -5156,191 +5157,6 @@ void write_lnum_adjust(linenr_T offset)
     curbuf->b_no_eol_lnum += offset;
 }
 
-#if defined(TEMPDIRNAMES) || defined(PROTO)
-static long temp_count = 0;             /* Temp filename counter. */
-
-/*
- * Delete the temp directory and all files it contains.
- */
-void vim_deltempdir(void)
-{
-  char_u      **files;
-  int file_count;
-  int i;
-
-  if (vim_tempdir != NULL) {
-    sprintf((char *)NameBuff, "%s*", vim_tempdir);
-    if (gen_expand_wildcards(1, &NameBuff, &file_count, &files,
-            EW_DIR|EW_FILE|EW_SILENT) == OK) {
-      for (i = 0; i < file_count; ++i)
-        os_remove((char *)files[i]);
-      FreeWild(file_count, files);
-    }
-    path_tail(NameBuff)[-1] = NUL;
-    os_rmdir((char *)NameBuff);
-
-    free(vim_tempdir);
-    vim_tempdir = NULL;
-  }
-}
-
-#endif
-
-#ifdef TEMPDIRNAMES
-/*
- * Directory "tempdir" was created.  Expand this name to a full path and put
- * it in "vim_tempdir".  This avoids that using ":cd" would confuse us.
- * "tempdir" must be no longer than MAXPATHL.
- */
-static void vim_settempdir(char_u *tempdir)
-{
-  char_u *buf = verbose_try_malloc((size_t)MAXPATHL + 2);
-  if (buf) {
-    if (vim_FullName(tempdir, buf, MAXPATHL, FALSE) == FAIL)
-      STRCPY(buf, tempdir);
-    add_pathsep(buf);
-    vim_tempdir = vim_strsave(buf);
-    free(buf);
-  }
-}
-#endif
-
-/*
- * vim_tempname(): Return a unique name that can be used for a temp file.
- *
- * The temp file is NOT created.
- *
- * The returned pointer is to allocated memory.
- * The returned pointer is NULL if no valid name was found.
- */
-char_u *
-vim_tempname (
-    int extra_char          /* char to use in the name instead of '?' */
-)
-{
-#ifdef USE_TMPNAM
-  char_u itmp[L_tmpnam];        /* use tmpnam() */
-#else
-  char_u itmp[TEMPNAMELEN];
-#endif
-
-#ifdef TEMPDIRNAMES
-  static char *(tempdirs[]) = {TEMPDIRNAMES};
-  int i;
-
-  /*
-   * This will create a directory for private use by this instance of Vim.
-   * This is done once, and the same directory is used for all temp files.
-   * This method avoids security problems because of symlink attacks et al.
-   * It's also a bit faster, because we only need to check for an existing
-   * file when creating the directory and not for each temp file.
-   */
-  if (vim_tempdir == NULL) {
-    /*
-     * Try the entries in TEMPDIRNAMES to create the temp directory.
-     */
-    for (i = 0; i < (int)(sizeof(tempdirs) / sizeof(char *)); ++i) {
-# ifndef HAVE_MKDTEMP
-      size_t itmplen;
-      long nr;
-      long off;
-# endif
-
-      /* expand $TMP, leave room for "/v1100000/999999999" */
-      expand_env((char_u *)tempdirs[i], itmp, TEMPNAMELEN - 20);
-      if (os_isdir(itmp)) {                    /* directory exists */
-        add_pathsep(itmp);
-
-# ifdef HAVE_MKDTEMP
-        /* Leave room for filename */
-        STRCAT(itmp, "vXXXXXX");
-        if (mkdtemp((char *)itmp) != NULL)
-          vim_settempdir(itmp);
-# else
-        /* Get an arbitrary number of up to 6 digits.  When it's
-         * unlikely that it already exists it will be faster,
-         * otherwise it doesn't matter.  The use of mkdir() avoids any
-         * security problems because of the predictable number. */
-        nr = (os_get_pid() + (long)time(NULL)) % 1000000L;
-        itmplen = STRLEN(itmp);
-
-        /* Try up to 10000 different values until we find a name that
-         * doesn't exist. */
-        for (off = 0; off < 10000L; ++off) {
-          int r;
-#  if defined(UNIX)
-          mode_t umask_save;
-#  endif
-
-          sprintf((char *)itmp + itmplen, "v%" PRId64, (int64_t)(nr + off));
-#  ifndef EEXIST
-          /* If mkdir() does not set errno to EEXIST, check for
-           * existing file here.  There is a race condition then,
-           * although it's fail-safe. */
-          if (os_file_exists(itmp))
-            continue;
-#  endif
-#  if defined(UNIX)
-          /* Make sure the umask doesn't remove the executable bit.
-           * "repl" has been reported to use "177". */
-          umask_save = umask(077);
-#  endif
-          r = os_mkdir((char *)itmp, 0700);
-#  if defined(UNIX)
-          (void)umask(umask_save);
-#  endif
-          if (r == 0) {
-            vim_settempdir(itmp);
-            break;
-          }
-#  ifdef EEXIST
-          /* If the mkdir() didn't fail because the file/dir exists,
-           * we probably can't create any dir here, try another
-           * place. */
-          if (errno != EEXIST)
-#  endif
-          break;
-        }
-# endif /* HAVE_MKDTEMP */
-        if (vim_tempdir != NULL)
-          break;
-      }
-    }
-  }
-
-  if (vim_tempdir != NULL) {
-    /* There is no need to check if the file exists, because we own the
-     * directory and nobody else creates a file in it. */
-    sprintf((char *)itmp, "%s%" PRId64, vim_tempdir, (int64_t)temp_count++);
-    return vim_strsave(itmp);
-  }
-
-  return NULL;
-
-#else /* TEMPDIRNAMES */
-
-
-#  ifdef USE_TMPNAM
-  char_u      *p;
-
-  /* tmpnam() will make its own name */
-  p = tmpnam((char *)itmp);
-  if (p == NULL || *p == NUL)
-    return NULL;
-#  else
-  char_u      *p;
-
-  STRCPY(itmp, TEMPNAME);
-  if ((p = vim_strchr(itmp, '?')) != NULL)
-    *p = extra_char;
-  if (mktemp((char *)itmp) == NULL)
-    return NULL;
-#  endif
-
-  return vim_strsave(itmp);
-#endif /* TEMPDIRNAMES */
-}
-
 #if defined(BACKSLASH_IN_FILENAME) || defined(PROTO)
 /*
  * Convert all backslashes in fname to forward slashes in-place.
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index 871674907b..cdfa882a3e 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -536,11 +536,6 @@ EXTERN int ru_col;              /* column for ruler */
 EXTERN int ru_wid;              /* 'rulerfmt' width of ruler when non-zero */
 EXTERN int sc_col;              /* column for shown command */
 
-#ifdef TEMPDIRNAMES
-EXTERN char_u   *vim_tempdir INIT(= NULL); /* Name of Vim's own temp dir.
-                                              Ends in a slash. */
-#endif
-
 /*
  * When starting or exiting some things are done differently (e.g. screen
  * updating).
diff --git a/src/nvim/hardcopy.c b/src/nvim/hardcopy.c
index e67cb67c69..64a5879d7d 100644
--- a/src/nvim/hardcopy.c
+++ b/src/nvim/hardcopy.c
@@ -40,6 +40,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/term.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/os/os.h"
 
@@ -2346,7 +2347,7 @@ int mch_print_init(prt_settings_T *psettings, char_u *jobname, int forceit)
 
   /* If the user didn't specify a file name, use a temp file. */
   if (psettings->outfile == NULL) {
-    prt_ps_file_name = vim_tempname('p');
+    prt_ps_file_name = vim_tempname();
     if (prt_ps_file_name == NULL) {
       EMSG(_(e_notmp));
       return FAIL;
diff --git a/src/nvim/if_cscope.c b/src/nvim/if_cscope.c
index 9ce0eb7fa0..9e07a60ee1 100644
--- a/src/nvim/if_cscope.c
+++ b/src/nvim/if_cscope.c
@@ -28,6 +28,7 @@
 #include "nvim/quickfix.h"
 #include "nvim/strings.h"
 #include "nvim/tag.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/window.h"
 #include "nvim/os/os.h"
@@ -1044,7 +1045,7 @@ static int cs_find_common(char *opt, char *pat, int forceit, int verbose, int us
   if (qfpos != NULL && *qfpos != '0' && totmatches > 0) {
     /* fill error list */
     FILE        *f;
-    char_u      *tmp = vim_tempname('c');
+    char_u      *tmp = vim_tempname();
     qf_info_T   *qi = NULL;
     win_T       *wp = NULL;
 
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 2fb404a148..a10fc2b8c5 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -69,6 +69,7 @@
 #include "nvim/spell.h"
 #include "nvim/strings.h"
 #include "nvim/term.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
 #include "nvim/window.h"
@@ -490,7 +491,7 @@ void ml_open_file(buf_T *buf)
 
   /* For a spell buffer use a temp file name. */
   if (buf->b_spell) {
-    fname = vim_tempname('s');
+    fname = vim_tempname();
     if (fname != NULL)
       (void)mf_open_file(mfp, fname);           /* consumes fname! */
     buf->b_may_swap = FALSE;
@@ -589,9 +590,7 @@ void ml_close_all(int del_file)
     ml_close(buf, del_file && ((buf->b_flags & BF_PRESERVED) == 0
                                || vim_strchr(p_cpo, CPO_PRESERVE) == NULL));
   spell_delete_wordlist();      /* delete the internal wordlist */
-#ifdef TEMPDIRNAMES
   vim_deltempdir();             /* delete created temp directory */
-#endif
 }
 
 /*
diff --git a/src/nvim/misc1.c b/src/nvim/misc1.c
index 3fc078cb8a..6ba1e68d64 100644
--- a/src/nvim/misc1.c
+++ b/src/nvim/misc1.c
@@ -52,6 +52,7 @@
 #include "nvim/strings.h"
 #include "nvim/tag.h"
 #include "nvim/term.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
 #include "nvim/window.h"
@@ -3423,7 +3424,7 @@ get_cmd_output (
     return NULL;
 
   /* get a name for the temp file */
-  if ((tempname = vim_tempname('o')) == NULL) {
+  if ((tempname = vim_tempname()) == NULL) {
     EMSG(_(e_notmp));
     return NULL;
   }
diff --git a/src/nvim/os/fs.c b/src/nvim/os/fs.c
index dce95eb3c9..46aea2bf36 100644
--- a/src/nvim/os/fs.c
+++ b/src/nvim/os/fs.c
@@ -3,6 +3,13 @@
 
 #include <assert.h>
 
+// TODO(hinidu): remove after implementing `os_mkdtemp` on top of libuv
+#ifdef WIN32
+# include <io.h>
+#else
+# include <stdlib.h>
+#endif
+
 #include "nvim/os/os.h"
 #include "nvim/ascii.h"
 #include "nvim/memory.h"
@@ -285,6 +292,21 @@ int os_mkdir(const char *path, int32_t mode)
   return result;
 }
 
+/// Create a unique temporary directory.
+/// TODO(hinidu): Implement on top of libuv. ref #850
+///
+/// @param[in,out] template Template of the path to the directory with XXXXXX
+///                         which would be replaced by random chars.
+/// @return Pointer to changed `template` for success, `NULL` for failure.
+char *os_mkdtemp(char *template)
+{
+#ifdef WIN32
+  return _mktemp(template) && os_mkdir(template, 0700) == 0 ? template : NULL;
+#else
+  return mkdtemp(template);
+#endif
+}
+
 /// Remove a directory.
 ///
 /// @return `0` for success, non-zero for failure.
diff --git a/src/nvim/os/os.h b/src/nvim/os/os.h
index b6148e72bf..69bd1ff4fd 100644
--- a/src/nvim/os/os.h
+++ b/src/nvim/os/os.h
@@ -13,4 +13,5 @@
 # include "os/env.h.generated.h"
 # include "os/users.h.generated.h"
 #endif
+
 #endif  // NVIM_OS_OS_H
diff --git a/src/nvim/os/os_defs.h b/src/nvim/os/os_defs.h
new file mode 100644
index 0000000000..aa6c5bccc3
--- /dev/null
+++ b/src/nvim/os/os_defs.h
@@ -0,0 +1,10 @@
+#ifndef NVIM_OS_OS_DEFS_H
+#define NVIM_OS_OS_DEFS_H
+
+#ifdef WIN32
+# include "nvim/os/win_defs.h"
+#else
+# include "nvim/os/unix_defs.h"
+#endif
+
+#endif  // NVIM_OS_DEFS_H
diff --git a/src/nvim/os/server.c b/src/nvim/os/server.c
index 23f9393122..2e8934ecfb 100644
--- a/src/nvim/os/server.c
+++ b/src/nvim/os/server.c
@@ -11,7 +11,7 @@
 #include "nvim/vim.h"
 #include "nvim/memory.h"
 #include "nvim/message.h"
-#include "nvim/fileio.h"
+#include "nvim/tempfile.h"
 #include "nvim/map.h"
 
 #define MAX_CONNECTIONS 32
@@ -52,7 +52,7 @@ void server_init(void)
   servers = pmap_new(cstr_t)();
 
   if (!os_getenv("NEOVIM_LISTEN_ADDRESS")) {
-    char *listen_address = (char *)vim_tempname('s');
+    char *listen_address = (char *)vim_tempname();
     os_setenv("NEOVIM_LISTEN_ADDRESS", listen_address, 1);
     free(listen_address);
   }
diff --git a/src/nvim/os/unix_defs.h b/src/nvim/os/unix_defs.h
new file mode 100644
index 0000000000..197a87bcc5
--- /dev/null
+++ b/src/nvim/os/unix_defs.h
@@ -0,0 +1,7 @@
+#ifndef NEOVIM_OS_UNIX_DEFS_H
+#define NEOVIM_OS_UNIX_DEFS_H
+
+#define TEMP_DIR_NAMES {"$TMPDIR", "/tmp", ".", "$HOME"}
+#define TEMP_FILE_PATH_MAXLEN 256
+
+#endif  // NEOVIM_OS_UNIX_DEFS_H
diff --git a/src/nvim/os/win_defs.h b/src/nvim/os/win_defs.h
new file mode 100644
index 0000000000..49fcb64777
--- /dev/null
+++ b/src/nvim/os/win_defs.h
@@ -0,0 +1,9 @@
+#ifndef NEOVIM_OS_WIN_DEFS_H
+#define NEOVIM_OS_WIN_DEFS_H
+
+#include <windows.h>
+
+#define TEMP_DIR_NAMES {"$TMP", "$TEMP", "$USERPROFILE", ""}
+#define TEMP_FILE_PATH_MAXLEN _MAX_PATH
+
+#endif  // NEOVIM_OS_WIN_DEFS_H
diff --git a/src/nvim/os_unix.c b/src/nvim/os_unix.c
index 2c657bebeb..4a0fbf5c18 100644
--- a/src/nvim/os_unix.c
+++ b/src/nvim/os_unix.c
@@ -52,6 +52,7 @@
 #include "nvim/screen.h"
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
+#include "nvim/tempfile.h"
 #include "nvim/term.h"
 #include "nvim/ui.h"
 #include "nvim/os/os.h"
@@ -1034,7 +1035,7 @@ int mch_expand_wildcards(int num_pat, char_u **pat, int *num_file,
   /*
    * get a name for the temp file
    */
-  if ((tempname = vim_tempname('o')) == NULL) {
+  if ((tempname = vim_tempname()) == NULL) {
     EMSG(_(e_notmp));
     return FAIL;
   }
diff --git a/src/nvim/os_unix_defs.h b/src/nvim/os_unix_defs.h
index 5ba9d2d98d..0d79117bfd 100644
--- a/src/nvim/os_unix_defs.h
+++ b/src/nvim/os_unix_defs.h
@@ -204,9 +204,6 @@
   "~/.nvim,$VIM/vimfiles,$VIMRUNTIME,$VIM/vimfiles/after,~/.nvim/after"
 #  endif
 
-#  define TEMPDIRNAMES  "$TMPDIR", "/tmp", ".", "$HOME"
-#  define TEMPNAMELEN    256
-
 /* Special wildcards that need to be handled by the shell */
 #define SPECIAL_WILDCHAR    "`'{"
 
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index ec95c74fef..ff2123bac1 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -47,6 +47,7 @@
 #include "nvim/search.h"
 #include "nvim/strings.h"
 #include "nvim/term.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/window.h"
 #include "nvim/os/os.h"
@@ -2537,7 +2538,7 @@ static char_u *get_mef_name(void)
   static int off = 0;
 
   if (*p_mef == NUL) {
-    name = vim_tempname('e');
+    name = vim_tempname();
     if (name == NULL)
       EMSG(_(e_notmp));
     return name;
diff --git a/src/nvim/spell.c b/src/nvim/spell.c
index c2354bb2c6..8ef67c95f7 100644
--- a/src/nvim/spell.c
+++ b/src/nvim/spell.c
@@ -322,6 +322,7 @@
 #include "nvim/strings.h"
 #include "nvim/syntax.h"
 #include "nvim/term.h"
+#include "nvim/tempfile.h"
 #include "nvim/ui.h"
 #include "nvim/undo.h"
 #include "nvim/os/os.h"
@@ -7814,7 +7815,7 @@ spell_add_word (
 
   if (idx == 0) {           // use internal wordlist
     if (int_wordlist == NULL) {
-      int_wordlist = vim_tempname('s');
+      int_wordlist = vim_tempname();
       if (int_wordlist == NULL)
         return;
     }
diff --git a/src/nvim/tempfile.c b/src/nvim/tempfile.c
new file mode 100644
index 0000000000..41fc163936
--- /dev/null
+++ b/src/nvim/tempfile.c
@@ -0,0 +1,131 @@
+#include <inttypes.h>
+#include <stdbool.h>
+#include <stdlib.h>
+#include <stdio.h>
+
+#include "nvim/ascii.h"
+#include "nvim/memory.h"
+#include "nvim/misc1.h"
+#include "nvim/os/os.h"
+#include "nvim/os/os_defs.h"
+#include "nvim/path.h"
+#include "nvim/strings.h"
+#include "nvim/tempfile.h"
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "tempfile.c.generated.h"
+#endif
+
+/// Name of Vim's own temp dir. Ends in a slash.
+static char_u *vim_tempdir = NULL;
+
+/// Create a directory for private use by this instance of Neovim.
+/// This is done once, and the same directory is used for all temp files.
+/// This method avoids security problems because of symlink attacks et al.
+/// It's also a bit faster, because we only need to check for an existing
+/// file when creating the directory and not for each temp file.
+static void vim_maketempdir(void)
+{
+  static const char *temp_dirs[] = TEMP_DIR_NAMES;
+  // Try the entries in `TEMP_DIR_NAMES` to create the temp directory.
+  char_u itmp[TEMP_FILE_PATH_MAXLEN];
+  for (size_t i = 0; i < sizeof(temp_dirs) / sizeof(char *); ++i) {
+    // Expand environment variables, leave room for "/nvimXXXXXX/999999999"
+    expand_env((char_u *)temp_dirs[i], itmp, TEMP_FILE_PATH_MAXLEN - 22);
+    if (!os_isdir(itmp)) {  // directory doesn't exist
+      continue;
+    }
+
+    add_pathsep(itmp);
+    // Concatenate with temporary directory name pattern
+    STRCAT(itmp, "nvimXXXXXX");
+    if (!os_mkdtemp((char *)itmp)) {
+      continue;
+    }
+    if (vim_settempdir(itmp)) {
+      // Successfully created and set temporary directory so stop trying.
+      break;
+    } else {
+      // Couldn't set `vim_tempdir` to itmp so remove created directory.
+      os_rmdir((char *)itmp);
+    }
+  }
+}
+
+/// Delete the temp directory and all files it contains.
+void vim_deltempdir(void)
+{
+  if (vim_tempdir != NULL) {
+    snprintf((char *)NameBuff, MAXPATHL, "%s*", vim_tempdir);
+
+    char_u **files;
+    int file_count;
+    if (gen_expand_wildcards(1, &NameBuff, &file_count, &files,
+        EW_DIR|EW_FILE|EW_SILENT) == OK) {
+      for (int i = 0; i < file_count; ++i) {
+        os_remove((char *)files[i]);
+      }
+      FreeWild(file_count, files);
+    }
+    path_tail(NameBuff)[-1] = NUL;
+    os_rmdir((char *)NameBuff);
+
+    free(vim_tempdir);
+    vim_tempdir = NULL;
+  }
+}
+
+/// Get the name of temp directory. This directory would be created on the first
+/// call to this function.
+char_u *vim_gettempdir(void)
+{
+  if (vim_tempdir == NULL) {
+    vim_maketempdir();
+  }
+
+  return vim_tempdir;
+}
+
+/// Set Neovim own temporary directory name to `tempdir`. This directory should
+/// be already created. Expand this name to a full path and put it in
+/// `vim_tempdir`. This avoids that using `:cd` would confuse us.
+///
+/// @param tempdir must be no longer than MAXPATHL.
+///
+/// @return false if we run out of memory.
+static bool vim_settempdir(char_u *tempdir)
+{
+  char_u *buf = verbose_try_malloc((size_t)MAXPATHL + 2);
+  if (!buf) {
+    return false;
+  }
+  vim_FullName(tempdir, buf, MAXPATHL, false);
+  add_pathsep(buf);
+  vim_tempdir = vim_strsave(buf);
+  free(buf);
+  return true;
+}
+
+/// Return a unique name that can be used for a temp file.
+///
+/// @note The temp file is NOT created.
+///
+/// @return pointer to the temp file name or NULL if Neovim can't create
+///         temporary directory for its own temporary files.
+char_u *vim_tempname(void)
+{
+  // Temp filename counter.
+  static uint32_t temp_count;
+
+  char_u *tempdir = vim_gettempdir();
+  if (!tempdir) {
+    return NULL;
+  }
+
+  // There is no need to check if the file exists, because we own the directory
+  // and nobody else creates a file in it.
+  char_u itmp[TEMP_FILE_PATH_MAXLEN];
+  snprintf((char *)itmp, TEMP_FILE_PATH_MAXLEN,
+           "%s%" PRIu32, tempdir, temp_count++);
+  return vim_strsave(itmp);
+}
diff --git a/src/nvim/tempfile.h b/src/nvim/tempfile.h
new file mode 100644
index 0000000000..c030a70eeb
--- /dev/null
+++ b/src/nvim/tempfile.h
@@ -0,0 +1,8 @@
+#ifndef NVIM_TEMPFILE_H
+#define NVIM_TEMPFILE_H
+
+#ifdef INCLUDE_GENERATED_DECLARATIONS
+# include "tempfile.h.generated.h"
+#endif
+
+#endif  // NVIM_TEMPFILE_H
diff --git a/test/unit/tempfile_spec.lua b/test/unit/tempfile_spec.lua
new file mode 100644
index 0000000000..adc52b9a8f
--- /dev/null
+++ b/test/unit/tempfile_spec.lua
@@ -0,0 +1,61 @@
+local lfs = require 'lfs'
+local helpers = require 'test.unit.helpers'
+
+local os = helpers.cimport './src/nvim/os/os.h'
+local tempfile = helpers.cimport './src/nvim/tempfile.h'
+
+describe('tempfile related functions', function()
+  after_each(function()
+    -- This won't work because vim_deltempdir() uses global buffer
+    -- that is initialized in main() and main() is not called for unit tests.
+    -- But it is not a big problem: all tests can work with or without it.
+    -- tempfile.vim_deltempdir()
+  end)
+
+  local vim_gettempdir = function()
+    return helpers.ffi.string(tempfile.vim_gettempdir())
+  end
+
+  describe('vim_gettempdir', function()
+    it('returns path to Neovim own temp directory', function()
+      local dir = vim_gettempdir()
+      assert.True(dir ~= nil and dir:len() > 0)
+      -- os_file_is_writable returns 2 for a directory which we have rights
+      -- to write into.
+      assert.equals(os.os_file_is_writable(helpers.to_cstr(dir)), 2)
+      for entry in lfs.dir(dir) do
+        assert.True(entry == '.' or entry == '..')
+      end
+    end)
+
+    it('returns the same directory on each call', function()
+      local dir1 = vim_gettempdir()
+      local dir2 = vim_gettempdir()
+      assert.equals(dir1, dir2)
+    end)
+  end)
+
+  describe('vim_tempname', function()
+    local vim_tempname = function()
+      return helpers.ffi.string(tempfile.vim_tempname())
+    end
+
+    it('generate name of non-existing file', function()
+      local file = vim_tempname()
+      assert.truthy(file)
+      assert.False(os.os_file_exists(file))
+    end)
+
+    it('generate different names on each call', function()
+      local fst = vim_tempname()
+      local snd = vim_tempname()
+      assert.not_equals(fst, snd)
+    end)
+
+    it('generate file name in Neovim own temp directory', function()
+      local dir = vim_gettempdir()
+      local file = vim_tempname()
+      assert.truthy(file:find('^' .. dir .. '[^/]*$'))
+    end)
+  end)
+end)