diff --git a/runtime/doc/eval.txt b/runtime/doc/eval.txt
index 9a1f4a426f..2a73590c76 100644
--- a/runtime/doc/eval.txt
+++ b/runtime/doc/eval.txt
@@ -22,6 +22,8 @@ done, the features in this document are not available.	See |+eval| and
 There are six types of variables:
 
 Number		A 32 or 64 bit signed number.  |expr-number| *Number*
+		64-bit Number is available only when compiled with the
+		|+num64| feature.
 		Examples:  -123  0x10  0177  0b1011
 
 Float		A floating point number. |floating-point-format| *Float*
@@ -887,6 +889,11 @@ When dividing a Number by zero the result depends on the value:
 	 <0 / 0  = -0x7fffffff	(like negative infinity)
 	(before Vim 7.2 it was always 0x7fffffff)
 
+When 64-bit Number support is enabled:
+	  0 / 0  = -0x8000000000000000	(like NaN for Float)
+	 >0 / 0  =  0x7fffffffffffffff	(like positive infinity)
+	 <0 / 0  = -0x7fffffffffffffff	(like negative infinity)
+
 When the righthand side of '%' is zero, the result is 0.
 
 None of these work for |Funcref|s.
@@ -3546,17 +3553,19 @@ float2nr({expr})					*float2nr()*
 		decimal point.
 		{expr} must evaluate to a |Float| or a Number.
 		When the value of {expr} is out of range for a |Number| the
-		result is truncated to 0x7fffffff or -0x7fffffff.  NaN results
-		in -0x80000000.
+		result is truncated to 0x7fffffff or -0x7fffffff (or when
+		64-bit Number support is enabled, 0x7fffffffffffffff or
+		-0x7fffffffffffffff.  NaN results in -0x80000000 (or when
+		64-bit Number support is enabled, -0x8000000000000000).
 		Examples: >
 			echo float2nr(3.95)
 <			3  >
 			echo float2nr(-23.45)
 <			-23  >
 			echo float2nr(1.0e100)
-<			2147483647  >
+<			2147483647  (or 9223372036854775807) >
 			echo float2nr(-1.0e150)
-<			-2147483647  >
+<			-2147483647 (or -9223372036854775807) >
 			echo float2nr(1.0e-100)
 <			0
 
@@ -7996,7 +8005,10 @@ winwidth({nr})						*winwidth()*
   :if winwidth(0) <= 50
   :  exe "normal 50\<C-W>|"
   :endif
-<
+<               For getting the terminal or screen size, see the 'columns'
+               option.
+
+
 wordcount()						*wordcount()*
 		The result is a dictionary of byte/chars/word statistics for
 		the current buffer.  This is the same info as provided by
@@ -8150,6 +8162,7 @@ mouseshape		Compiled with support for 'mouseshape'.
 multi_byte		Compiled with support for 'encoding'
 multi_byte_encoding	'encoding' is set to a multi-byte encoding.
 multi_lang		Compiled with support for multiple languages.
+num64			Compiled with 64-bit |Number| support.
 nvim			This is Nvim. |has-patch|
 path_extra		Compiled with up/downwards search in 'path' and 'tags'
 persistent_undo		Compiled with support for persistent undo history.
diff --git a/runtime/doc/various.txt b/runtime/doc/various.txt
index 2679c2dabb..8880b625e9 100644
--- a/runtime/doc/various.txt
+++ b/runtime/doc/various.txt
@@ -352,6 +352,7 @@ N  *+mouseshape*	|'mouseshape'|
 N  *+multi_byte*	16 and 32 bit characters |multibyte|
    *+multi_byte_ime*	Win32 input method for multibyte chars |multibyte-ime|
 N  *+multi_lang*	non-English language support |multi-lang|
+   *+num64*		64-bit Number support |Number|
 N  *+path_extra*	Up/downwards search in 'path' and 'tags'
 N  *+persistent_undo*	Persistent undo |undo-persistence|
    *+postscript*	|:hardcopy| writes a PostScript file
diff --git a/src/nvim/buffer.h b/src/nvim/buffer.h
index 39b9faf8b1..609567fbcd 100644
--- a/src/nvim/buffer.h
+++ b/src/nvim/buffer.h
@@ -83,14 +83,16 @@ static inline void restore_win_for_buf(win_T *save_curwin,
   }
 }
 
-static inline void buf_set_changedtick(buf_T *const buf, const int changedtick)
+static inline void buf_set_changedtick(buf_T *const buf,
+                                       const varnumber_T changedtick)
   REAL_FATTR_NONNULL_ALL REAL_FATTR_ALWAYS_INLINE;
 
 /// Set b_changedtick and corresponding variable
 ///
 /// @param[out]  buf  Buffer to set changedtick in.
 /// @param[in]  changedtick  New value.
-static inline void buf_set_changedtick(buf_T *const buf, const int changedtick)
+static inline void buf_set_changedtick(buf_T *const buf,
+                                       const varnumber_T changedtick)
 {
 #ifndef NDEBUG
   dictitem_T *const changedtick_di = tv_dict_find(
diff --git a/src/nvim/charset.c b/src/nvim/charset.c
index 5a0590d075..48db1030a6 100644
--- a/src/nvim/charset.c
+++ b/src/nvim/charset.c
@@ -1621,13 +1621,13 @@ bool vim_isblankline(char_u *lbuf)
 /// @param unptr Returns the unsigned result.
 /// @param maxlen Max length of string to check.
 void vim_str2nr(const char_u *const start, int *const prep, int *const len,
-                const int what, long *const nptr, unsigned long *const unptr,
-                const int maxlen)
+                const int what, varnumber_T *const nptr,
+                uvarnumber_T *const unptr, const int maxlen)
 {
   const char_u *ptr = start;
   int pre = 0;  // default is decimal
   bool negative = false;
-  unsigned long un = 0;
+  uvarnumber_T un = 0;
 
   if (ptr[0] == '-') {
     negative = true;
@@ -1683,7 +1683,12 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
       n += 2;  // skip over "0b"
     }
     while ('0' <= *ptr && *ptr <= '1') {
-      un = 2 * un + (unsigned long)(*ptr - '0');
+      // avoid ubsan error for overflow
+      if (un < UVARNUMBER_MAX / 2) {
+        un = 2 * un + (uvarnumber_T)(*ptr - '0');
+      } else {
+        un = UVARNUMBER_MAX;
+      }
       ptr++;
       if (n++ == maxlen) {
         break;
@@ -1692,7 +1697,12 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
   } else if ((pre == '0') || what == STR2NR_OCT + STR2NR_FORCE) {
     // octal
     while ('0' <= *ptr && *ptr <= '7') {
-      un = 8 * un + (unsigned long)(*ptr - '0');
+      // avoid ubsan error for overflow
+      if (un < UVARNUMBER_MAX / 8) {
+        un = 8 * un + (uvarnumber_T)(*ptr - '0');
+      } else {
+        un = UVARNUMBER_MAX;
+      }
       ptr++;
       if (n++ == maxlen) {
         break;
@@ -1705,7 +1715,12 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
       n += 2;  // skip over "0x"
     }
     while (ascii_isxdigit(*ptr)) {
-      un = 16 * un + (unsigned long)hex2nr(*ptr);
+      // avoid ubsan error for overflow
+      if (un < UVARNUMBER_MAX / 16) {
+        un = 16 * un + (uvarnumber_T)hex2nr(*ptr);
+      } else {
+        un = UVARNUMBER_MAX;
+      }
       ptr++;
       if (n++ == maxlen) {
         break;
@@ -1714,7 +1729,12 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
   } else {
     // decimal
     while (ascii_isdigit(*ptr)) {
-      un = 10 * un + (unsigned long)(*ptr - '0');
+      // avoid ubsan error for overflow
+      if (un < UVARNUMBER_MAX / 10) {
+        un = 10 * un + (uvarnumber_T)(*ptr - '0');
+      } else {
+        un = UVARNUMBER_MAX;
+      }
       ptr++;
       if (n++ == maxlen) {
         break;
@@ -1731,11 +1751,18 @@ void vim_str2nr(const char_u *const start, int *const prep, int *const len,
   }
 
   if (nptr != NULL) {
-    if (negative) {
-      // account for leading '-' for decimal numbers
-      *nptr = -(long)un;
+    if (negative) {  // account for leading '-' for decimal numbers
+      // avoid ubsan error for overflow
+      if (un > VARNUMBER_MAX) {
+        *nptr = VARNUMBER_MIN;
+      } else {
+        *nptr = -(varnumber_T)un;
+      }
     } else {
-      *nptr = (long)un;
+      if (un > VARNUMBER_MAX) {
+        un = VARNUMBER_MAX;
+      }
+      *nptr = (varnumber_T)un;
     }
   }
 
diff --git a/src/nvim/eval.c b/src/nvim/eval.c
index 59d673fc00..94916e3e3c 100644
--- a/src/nvim/eval.c
+++ b/src/nvim/eval.c
@@ -6,6 +6,7 @@
  */
 
 #include <assert.h>
+#include <float.h>
 #include <inttypes.h>
 #include <stdarg.h>
 #include <string.h>
@@ -446,7 +447,7 @@ typedef struct {
   bool rpc;
   int refcount;
   Callback on_stdout, on_stderr, on_exit;
-  int *status_ptr;
+  varnumber_T *status_ptr;
   uint64_t id;
   MultiQueue *events;
 } TerminalJobData;
@@ -1081,10 +1082,10 @@ char_u *eval_to_string_safe(char_u *arg, char_u **nextcmd, int use_sandbox)
  * Evaluates "expr" silently.
  * Returns -1 for an error.
  */
-int eval_to_number(char_u *expr)
+varnumber_T eval_to_number(char_u *expr)
 {
   typval_T rettv;
-  int retval;
+  varnumber_T retval;
   char_u      *p = skipwhite(expr);
 
   ++emsg_off;
@@ -1203,7 +1204,7 @@ int call_vim_function(
     typval_T *rettv
 )
 {
-  long n;
+  varnumber_T n;
   int len;
   int doesrange;
   void        *save_funccalp = NULL;
@@ -1264,11 +1265,11 @@ int call_vim_function(
 /// @param[in]  safe  Use with sandbox.
 ///
 /// @return -1 when calling function fails, result of function otherwise.
-long call_func_retnr(char_u *func, int argc, const char_u *const *const argv,
-                     int safe)
+varnumber_T call_func_retnr(char_u *func, int argc,
+                            const char_u *const *const argv, int safe)
 {
   typval_T rettv;
-  long retval;
+  varnumber_T retval;
 
   /* All arguments are passed as strings, no conversion to number. */
   if (call_vim_function(func, argc, argv, safe, TRUE, &rettv) == FAIL)
@@ -1396,7 +1397,7 @@ void prof_child_exit(proftime_T *tm /* where waittime was stored */
 int eval_foldexpr(char_u *arg, int *cp)
 {
   typval_T tv;
-  int retval;
+  varnumber_T retval;
   char_u      *s;
   int use_sandbox = was_set_insecurely((char_u *)"foldexpr",
       OPT_LOCAL);
@@ -1429,7 +1430,7 @@ int eval_foldexpr(char_u *arg, int *cp)
     --sandbox;
   --textlock;
 
-  return retval;
+  return (int)retval;
 }
 
 /*
@@ -2283,7 +2284,7 @@ static char_u *get_lval(char_u *const name, typval_T *const rettv,
       if (empty1) {
         lp->ll_n1 = 0;
       } else {
-        lp->ll_n1 = tv_get_number(&var1);  // Is number or string.
+        lp->ll_n1 = (long)tv_get_number(&var1);  // Is number or string.
         tv_clear(&var1);
       }
       lp->ll_dict = NULL;
@@ -2312,7 +2313,7 @@ static char_u *get_lval(char_u *const name, typval_T *const rettv,
        * Otherwise "lp->ll_n2" is set to the second index.
        */
       if (lp->ll_range && !lp->ll_empty2) {
-        lp->ll_n2 = tv_get_number(&var2);  // Is number or string.
+        lp->ll_n2 = (long)tv_get_number(&var2);  // Is number or string.
         tv_clear(&var2);
         if (lp->ll_n2 < 0) {
           ni = tv_list_find(lp->ll_list, lp->ll_n2);
@@ -3522,7 +3523,7 @@ static int eval4(char_u **arg, typval_T *rettv, int evaluate)
   exptype_T type = TYPE_UNKNOWN;
   int type_is = FALSE;              /* TRUE for "is" and "isnot" */
   int len = 2;
-  long n1, n2;
+  varnumber_T n1, n2;
   int ic;
 
   /*
@@ -3784,7 +3785,7 @@ static int eval5(char_u **arg, typval_T *rettv, int evaluate)
   typval_T var2;
   typval_T var3;
   int op;
-  long n1, n2;
+  varnumber_T n1, n2;
   float_T f1 = 0, f2 = 0;
   char_u      *p;
 
@@ -3914,29 +3915,26 @@ static int eval5(char_u **arg, typval_T *rettv, int evaluate)
 
 // TODO(ZyX-I): move to eval/expressions
 
-/*
- * Handle fifth level expression:
- *	*	number multiplication
- *	/	number division
- *	%	number modulo
- *
- * "arg" must point to the first non-white of the expression.
- * "arg" is advanced to the next non-white after the recognized expression.
- *
- * Return OK or FAIL.
- */
-static int 
-eval6 (
-    char_u **arg,
-    typval_T *rettv,
-    int evaluate,
-    int want_string              /* after "." operator */
-)
+/// Handle fifth level expression:
+///  - *  number multiplication
+///  - /  number division
+///  - %  number modulo
+///
+/// @param[in,out]  arg  Points to the first non-whitespace character of the
+///                      expression.  Is advanced to the next non-whitespace
+///                      character after the recognized expression.
+/// @param[out]  rettv  Location where result is saved.
+/// @param[in]  evaluate  If not true, rettv is not populated.
+/// @param[in]  want_string  True if "." is string_concatenation, otherwise
+///                          float
+/// @return  OK or FAIL.
+static int eval6(char_u **arg, typval_T *rettv, int evaluate, int want_string)
+  FUNC_ATTR_NO_SANITIZE_UNDEFINED
 {
   typval_T var2;
   int op;
-  long n1, n2;
-  int use_float = FALSE;
+  varnumber_T n1, n2;
+  bool use_float = false;
   float_T f1 = 0, f2;
   bool error = false;
 
@@ -3957,7 +3955,7 @@ eval6 (
     if (evaluate) {
       if (rettv->v_type == VAR_FLOAT) {
         f1 = rettv->vval.v_float;
-        use_float = TRUE;
+        use_float = true;
         n1 = 0;
       } else {
         n1 = tv_get_number_chk(rettv, &error);
@@ -3981,7 +3979,7 @@ eval6 (
       if (var2.v_type == VAR_FLOAT) {
         if (!use_float) {
           f1 = n1;
-          use_float = TRUE;
+          use_float = true;
         }
         f2 = var2.vval.v_float;
         n2 = 0;
@@ -4024,18 +4022,20 @@ eval6 (
         rettv->v_type = VAR_FLOAT;
         rettv->vval.v_float = f1;
       } else {
-        if (op == '*')
+        if (op == '*') {
           n1 = n1 * n2;
-        else if (op == '/') {
-          if (n2 == 0) {                /* give an error message? */
-            if (n1 == 0)
-              n1 = -0x7fffffffL - 1L;                   /* similar to NaN */
-            else if (n1 < 0)
-              n1 = -0x7fffffffL;
-            else
-              n1 = 0x7fffffffL;
-          } else
+        } else if (op == '/') {
+          if (n2 == 0) {                // give an error message?
+            if (n1 == 0) {
+              n1 = VARNUMBER_MIN;  // similar to NaN
+            } else if (n1 < 0) {
+              n1 = -VARNUMBER_MAX;
+            } else {
+              n1 = VARNUMBER_MAX;
+            }
+          } else {
             n1 = n1 / n2;
+          }
         } else {
           if (n2 == 0)                  /* give an error message? */
             n1 = 0;
@@ -4084,7 +4084,7 @@ static int eval7(
     int want_string                 // after "." operator
 )
 {
-  long n;
+  varnumber_T n;
   int len;
   char_u      *s;
   char_u      *start_leader, *end_leader;
@@ -4282,7 +4282,7 @@ static int eval7(
   // Apply logical NOT and unary '-', from right to left, ignore '+'.
   if (ret == OK && evaluate && end_leader > start_leader) {
     bool error = false;
-    int val = 0;
+    varnumber_T val = 0;
     float_T f = 0.0;
 
     if (rettv->v_type == VAR_FLOAT) {
@@ -6688,7 +6688,7 @@ static void f_argv(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   int idx;
 
   if (argvars[0].v_type != VAR_UNKNOWN) {
-    idx = tv_get_number_chk(&argvars[0], NULL);
+    idx = (int)tv_get_number_chk(&argvars[0], NULL);
     if (idx >= 0 && idx < ARGCOUNT) {
       rettv->vval.v_string = (char_u *)xstrdup(
           (const char *)alist_name(&ARGLIST[idx]));
@@ -7424,7 +7424,7 @@ static void f_complete(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     return;
   }
 
-  const int startcol = tv_get_number_chk(&argvars[0], NULL);
+  const colnr_T startcol = tv_get_number_chk(&argvars[0], NULL);
   if (startcol <= 0) {
     return;
   }
@@ -7635,9 +7635,9 @@ static void f_cursor(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     }
   } else {
     line = tv_get_lnum(argvars);
-    col = tv_get_number_chk(&argvars[1], NULL);
+    col = (long)tv_get_number_chk(&argvars[1], NULL);
     if (argvars[2].v_type != VAR_UNKNOWN) {
-      coladd = tv_get_number_chk(&argvars[2], NULL);
+      coladd = (long)tv_get_number_chk(&argvars[2], NULL);
     }
   }
   if (line < 0 || col < 0
@@ -8191,7 +8191,7 @@ static void f_extend(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     } else if (!tv_check_lock(l1->lv_lock, arg_errmsg, TV_TRANSLATE)) {
       listitem_T *item;
       if (argvars[2].v_type != VAR_UNKNOWN) {
-        before = tv_get_number_chk(&argvars[2], &error);
+        before = (long)tv_get_number_chk(&argvars[2], &error);
         if (error) {
           return;  // Type error; errmsg already given.
         }
@@ -8560,9 +8560,9 @@ static void f_float2nr(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   float_T f;
 
   if (tv_get_float_chk(argvars, &f)) {
-    if (f < VARNUMBER_MIN) {
-      rettv->vval.v_number = VARNUMBER_MIN;
-    } else if (f > VARNUMBER_MAX) {
+    if (f <= -VARNUMBER_MAX + DBL_EPSILON) {
+      rettv->vval.v_number = -VARNUMBER_MAX;
+    } else if (f >= VARNUMBER_MAX - DBL_EPSILON) {
       rettv->vval.v_number = VARNUMBER_MAX;
     } else {
       rettv->vval.v_number = (varnumber_T)f;
@@ -10537,6 +10537,7 @@ static void f_has(typval_T *argvars, typval_T *rettv, FunPtr fptr)
     "mouse",
     "multi_byte",
     "multi_lang",
+    "num64",
     "packages",
     "path_extra",
     "persistent_undo",
@@ -12966,7 +12967,7 @@ static void f_range(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   varnumber_T start;
   varnumber_T end;
   varnumber_T stride = 1;
-  long i;
+  varnumber_T i;
   bool error = false;
 
   start = tv_get_number_chk(&argvars[0], &error);
@@ -13184,7 +13185,7 @@ static int list2proftime(typval_T *arg, proftime_T *tm) FUNC_ATTR_NONNULL_ALL
   // in f_reltime() we split up the 64-bit proftime_T into two 32-bit
   // values, now we combine them again.
   union {
-    struct { varnumber_T low, high; } split;
+    struct { int32_t low, high; } split;
     proftime_T prof;
   } u = { .split.high = n1, .split.low = n2 };
 
@@ -13225,7 +13226,7 @@ static void f_reltime(typval_T *argvars, typval_T *rettv, FunPtr fptr)
   // (varnumber_T is defined as int). For all our supported platforms, int's
   // are at least 32-bits wide. So we'll use two 32-bit values to store it.
   union {
-    struct { varnumber_T low, high; } split;
+    struct { int32_t low, high; } split;
     proftime_T prof;
   } u = { .prof = res };
 
@@ -15173,8 +15174,8 @@ static int item_compare(const void *s1, const void *s2, bool keep_zero)
   int res;
 
   if (sortinfo->item_compare_numbers) {
-    const long v1 = tv_get_number(tv1);
-    const long v2 = tv_get_number(tv2);
+    const varnumber_T v1 = tv_get_number(tv1);
+    const varnumber_T v2 = tv_get_number(tv2);
 
     res = v1 == v2 ? 0 : v1 > v2 ? 1 : -1;
     goto item_compare_end;
@@ -15722,7 +15723,7 @@ static void f_str2float(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 static void f_str2nr(typval_T *argvars, typval_T *rettv, FunPtr fptr)
 {
   int base = 10;
-  long n;
+  varnumber_T n;
   int what;
 
   if (argvars[1].v_type != VAR_UNKNOWN) {
@@ -18138,7 +18139,7 @@ static int eval_isnamec1(int c)
 /*
  * Get number v: variable value.
  */
-long get_vim_var_nr(int idx) FUNC_ATTR_PURE
+varnumber_T get_vim_var_nr(int idx) FUNC_ATTR_PURE
 {
   return vimvars[idx].vv_nr;
 }
diff --git a/src/nvim/eval/decode.c b/src/nvim/eval/decode.c
index 935c98fb84..9c9c2c2dc8 100644
--- a/src/nvim/eval/decode.c
+++ b/src/nvim/eval/decode.c
@@ -435,8 +435,8 @@ static inline int parse_json_string(const char *const buf, const size_t buf_len,
         case 'u': {
           const char ubuf[] = { t[1], t[2], t[3], t[4] };
           t += 4;
-          unsigned long ch;
-          vim_str2nr((char_u *) ubuf, NULL, NULL,
+          uvarnumber_T ch;
+          vim_str2nr((char_u *)ubuf, NULL, NULL,
                      STR2NR_HEX | STR2NR_FORCE, NULL, &ch, 4);
           if (ch == 0) {
             hasnul = true;
@@ -609,7 +609,7 @@ parse_json_number_check:
     tv.v_type = VAR_FLOAT;
   } else {
     // Convert integer
-    long nr;
+    varnumber_T nr;
     int num_len;
     vim_str2nr((char_u *) s, NULL, &num_len, 0, &nr, NULL, (int) (p - s));
     if ((int) exp_num_len != num_len) {
@@ -617,7 +617,7 @@ parse_json_number_check:
               "to integer vim_str2nr consumed %i bytes in place of %zu"),
             (int) exp_num_len, s, num_len, exp_num_len);
     }
-    tv.vval.v_number = (varnumber_T) nr;
+    tv.vval.v_number = nr;
   }
   if (json_decoder_pop(OBJ(tv, false, *didcomma, *didcolon),
                        stack, container_stack,
diff --git a/src/nvim/eval/executor.c b/src/nvim/eval/executor.c
index 91bb61323f..99298cbbcf 100644
--- a/src/nvim/eval/executor.c
+++ b/src/nvim/eval/executor.c
@@ -25,7 +25,7 @@ char *e_listidx = N_("E684: list index out of range: %" PRId64);
 /// @return OK or FAIL.
 int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2,
                 const char *const op)
-  FUNC_ATTR_NONNULL_ALL
+  FUNC_ATTR_NONNULL_ALL FUNC_ATTR_NO_SANITIZE_UNDEFINED
 {
   // Can't do anything with a Funcref, a Dict or special value on the right.
   if (tv2->v_type != VAR_FUNC && tv2->v_type != VAR_DICT) {
@@ -55,7 +55,7 @@ int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2,
           // nr += nr  or  nr -= nr
           varnumber_T n = tv_get_number(tv1);
           if (tv2->v_type == VAR_FLOAT) {
-            float_T f = n;
+            float_T f = (float_T)n;
 
             if (*op == '+') {
               f += tv2->vval.v_float;
@@ -99,7 +99,7 @@ int eexe_mod_op(typval_T *const tv1, const typval_T *const tv2,
         }
         const float_T f = (tv2->v_type == VAR_FLOAT
                            ? tv2->vval.v_float
-                           : tv_get_number(tv2));
+                           : (float_T)tv_get_number(tv2));
         if (*op == '+') {
           tv1->vval.v_float += f;
         } else {
diff --git a/src/nvim/eval/typval.c b/src/nvim/eval/typval.c
index f017f57b12..4521085519 100644
--- a/src/nvim/eval/typval.c
+++ b/src/nvim/eval/typval.c
@@ -2405,9 +2405,7 @@ varnumber_T tv_get_number_chk(const typval_T *const tv, bool *const ret_error)
     case VAR_STRING: {
       varnumber_T n = 0;
       if (tv->vval.v_string != NULL) {
-        long nr;
-        vim_str2nr(tv->vval.v_string, NULL, NULL, STR2NR_ALL, &nr, NULL, 0);
-        n = (varnumber_T)nr;
+        vim_str2nr(tv->vval.v_string, NULL, NULL, STR2NR_ALL, &n, NULL, 0);
       }
       return n;
     }
@@ -2444,7 +2442,7 @@ varnumber_T tv_get_number_chk(const typval_T *const tv, bool *const ret_error)
 linenr_T tv_get_lnum(const typval_T *const tv)
   FUNC_ATTR_NONNULL_ALL FUNC_ATTR_WARN_UNUSED_RESULT
 {
-  linenr_T lnum = tv_get_number_chk(tv, NULL);
+  linenr_T lnum = (linenr_T)tv_get_number_chk(tv, NULL);
   if (lnum == 0) {  // No valid number, try using same function as line() does.
     int fnum;
     pos_T *const fp = var2fpos(tv, true, &fnum);
diff --git a/src/nvim/eval/typval.h b/src/nvim/eval/typval.h
index 0f659727ee..3f8ed3b3f9 100644
--- a/src/nvim/eval/typval.h
+++ b/src/nvim/eval/typval.h
@@ -1,7 +1,7 @@
 #ifndef NVIM_EVAL_TYPVAL_H
 #define NVIM_EVAL_TYPVAL_H
 
-#include <limits.h>
+#include <inttypes.h>
 #include <stddef.h>
 #include <stdint.h>
 #include <string.h>
@@ -20,20 +20,21 @@
 #include "nvim/macros.h"
 
 /// Type used for VimL VAR_NUMBER values
-typedef int varnumber_T;
+typedef int64_t varnumber_T;
+typedef uint64_t uvarnumber_T;
 
 /// Type used for VimL VAR_FLOAT values
 typedef double float_T;
 
 /// Maximal possible value of varnumber_T variable
-#define VARNUMBER_MAX INT_MAX
+#define VARNUMBER_MAX INT64_MAX
+#define UVARNUMBER_MAX UINT64_MAX
 
 /// Mimimal possible value of varnumber_T variable
-#define VARNUMBER_MIN INT_MIN
-#define PRIdVARNUMBER "d"
+#define VARNUMBER_MIN INT64_MIN
 
 /// %d printf format specifier for varnumber_T
-#define PRIdVARNUMBER "d"
+#define PRIdVARNUMBER PRId64
 
 typedef struct listvar_S list_T;
 typedef struct dictvar_S dict_T;
diff --git a/src/nvim/ex_cmds.c b/src/nvim/ex_cmds.c
index a528a65abb..008a44b43b 100644
--- a/src/nvim/ex_cmds.c
+++ b/src/nvim/ex_cmds.c
@@ -318,14 +318,12 @@ static int sort_abort;    ///< flag to indicate if sorting has been interrupted
 /// Struct to store info to be sorted.
 typedef struct {
   linenr_T lnum;          ///< line number
-  long start_col_nr;      ///< starting column number or number
-  long end_col_nr;        ///< ending column number
   union {
     struct {
-      long start_col_nr;  ///< starting column number
-      long end_col_nr;    ///< ending column number
+      varnumber_T start_col_nr;  ///< starting column number
+      varnumber_T end_col_nr;    ///< ending column number
     } line;
-    long value;           ///< value if sorting by integer
+    varnumber_T value;           ///< value if sorting by integer
     float_T value_flt;    ///< value if sorting by float
   } st_u;
 } sorti_T;
diff --git a/src/nvim/ex_getln.c b/src/nvim/ex_getln.c
index 36b6bac9c3..858374c68e 100644
--- a/src/nvim/ex_getln.c
+++ b/src/nvim/ex_getln.c
@@ -5002,7 +5002,7 @@ int get_list_range(char_u **str, int *num1, int *num2)
 {
   int len;
   int first = false;
-  long num;
+  varnumber_T num;
 
   *str = skipwhite(*str);
   if (**str == '-' || ascii_isdigit(**str)) {  // parse "from" part of range
diff --git a/src/nvim/fileio.c b/src/nvim/fileio.c
index 4063277403..be4188c4df 100644
--- a/src/nvim/fileio.c
+++ b/src/nvim/fileio.c
@@ -281,8 +281,8 @@ readfile (
   colnr_T len;
   long size = 0;
   char_u      *p = NULL;
-  off_t filesize = 0;
-  int skip_read = FALSE;
+  off_T filesize = 0;
+  int skip_read = false;
   context_sha256_T sha_ctx;
   int read_undo_file = FALSE;
   int split = 0;                        /* number of split lines */
@@ -777,9 +777,9 @@ retry:
     if (read_buffer) {
       read_buf_lnum = 1;
       read_buf_col = 0;
-    } else if (read_stdin || lseek(fd, (off_t)0L, SEEK_SET) != 0) {
-      /* Can't rewind the file, give up. */
-      error = TRUE;
+    } else if (read_stdin || vim_lseek(fd, (off_T)0L, SEEK_SET) != 0) {
+      // Can't rewind the file, give up.
+      error = true;
       goto failed;
     }
     /* Delete the previously read lines. */
@@ -1614,19 +1614,16 @@ rewind_retry:
             if (fileformat == EOL_DOS) {
               if (ptr[-1] == CAR) {             /* remove CR */
                 ptr[-1] = NUL;
-                --len;
-              }
-              /*
-               * Reading in Dos format, but no CR-LF found!
-               * When 'fileformats' includes "unix", delete all
-               * the lines read so far and start all over again.
-               * Otherwise give an error message later.
-               */
-              else if (ff_error != EOL_DOS) {
-                if (   try_unix
-                       && !read_stdin
-                       && (read_buffer
-                           || lseek(fd, (off_t)0L, SEEK_SET) == 0)) {
+                len--;
+              } else if (ff_error != EOL_DOS) {
+                // Reading in Dos format, but no CR-LF found!
+                // When 'fileformats' includes "unix", delete all
+                // the lines read so far and start all over again.
+                // Otherwise give an error message later.
+                if (try_unix
+                    && !read_stdin
+                    && (read_buffer
+                        || vim_lseek(fd, (off_T)0L, SEEK_SET) == 0)) {
                   fileformat = EOL_UNIX;
                   if (set_options)
                     set_fileformat(EOL_UNIX, OPT_LOCAL);
@@ -3833,7 +3830,7 @@ static bool msg_add_fileformat(int eol_type)
 /*
  * Append line and character count to IObuff.
  */
-void msg_add_lines(int insert_space, long lnum, off_t nchars)
+void msg_add_lines(int insert_space, long lnum, off_T nchars)
 {
   char_u  *p;
 
@@ -6870,8 +6867,8 @@ static bool apply_autocmds_group(event_T event, char_u *fname, char_u *fname_io,
     patcmd.next = active_apc_list;
     active_apc_list = &patcmd;
 
-    /* set v:cmdarg (only when there is a matching pattern) */
-    save_cmdbang = get_vim_var_nr(VV_CMDBANG);
+    // set v:cmdarg (only when there is a matching pattern)
+    save_cmdbang = (long)get_vim_var_nr(VV_CMDBANG);
     if (eap != NULL) {
       save_cmdarg = set_cmdarg(eap, NULL);
       set_vim_var_nr(VV_CMDBANG, (long)eap->forceit);
diff --git a/src/nvim/fold.c b/src/nvim/fold.c
index 9c44e89eed..db88791967 100644
--- a/src/nvim/fold.c
+++ b/src/nvim/fold.c
@@ -2894,7 +2894,7 @@ static void foldlevelExpr(fline_T *flp)
   /* KeyTyped may be reset to 0 when calling a function which invokes
    * do_cmdline().  To make 'foldopen' work correctly restore KeyTyped. */
   save_keytyped = KeyTyped;
-  n = eval_foldexpr(flp->wp->w_p_fde, &c);
+  n = (int)eval_foldexpr(flp->wp->w_p_fde, &c);
   KeyTyped = save_keytyped;
 
   switch (c) {
diff --git a/src/nvim/func_attr.h b/src/nvim/func_attr.h
index f1a1d9a563..bd26205d6d 100644
--- a/src/nvim/func_attr.h
+++ b/src/nvim/func_attr.h
@@ -95,6 +95,10 @@
 # undef FUNC_ATTR_NORETURN
 #endif
 
+#ifdef FUNC_ATTR_NO_SANITIZE_UNDEFINED
+# undef FUNC_ATTR_NO_SANITIZE_UNDEFINED
+#endif
+
 #ifndef DID_REAL_ATTR
 # define DID_REAL_ATTR
 # ifdef __GNUC__
@@ -122,6 +126,14 @@
 #   define REAL_FATTR_ALLOC_SIZE(x) __attribute__((alloc_size(x)))
 #   define REAL_FATTR_ALLOC_SIZE_PROD(x, y) __attribute__((alloc_size(x, y)))
 #  endif
+
+#  if NVIM_HAS_ATTRIBUTE(no_sanitize_undefined)
+#   define REAL_FATTR_NO_SANITIZE_UNDEFINED \
+      __attribute__((no_sanitize_undefined))
+#  elif NVIM_HAS_ATTRIBUTE(no_sanitize)
+#   define REAL_FATTR_NO_SANITIZE_UNDEFINED \
+      __attribute__((no_sanitize("undefined")))
+#  endif
 # endif
 
 // Define attributes that are not defined for this compiler.
@@ -177,6 +189,10 @@
 # ifndef REAL_FATTR_NORETURN
 #  define REAL_FATTR_NORETURN
 # endif
+
+# ifndef REAL_FATTR_NO_SANITIZE_UNDEFINED
+#  define REAL_FATTR_NO_SANITIZE_UNDEFINED
+# endif
 #endif
 
 #ifdef DEFINE_FUNC_ATTRIBUTES
@@ -198,6 +214,7 @@
 # define FUNC_ATTR_NONNULL_ARG(...) REAL_FATTR_NONNULL_ARG(__VA_ARGS__)
 # define FUNC_ATTR_NONNULL_RET REAL_FATTR_NONNULL_RET
 # define FUNC_ATTR_NORETURN REAL_FATTR_NORETURN
+# define FUNC_ATTR_NO_SANITIZE_UNDEFINED REAL_FATTR_NO_SANITIZE_UNDEFINED
 #elif !defined(DO_NOT_DEFINE_EMPTY_ATTRIBUTES)
 # define FUNC_ATTR_MALLOC
 # define FUNC_ATTR_ALLOC_SIZE(x)
@@ -212,4 +229,5 @@
 # define FUNC_ATTR_NONNULL_ARG(...)
 # define FUNC_ATTR_NONNULL_RET
 # define FUNC_ATTR_NORETURN
+# define FUNC_ATTR_NO_SANITIZE_UNDEFINED
 #endif
diff --git a/src/nvim/globals.h b/src/nvim/globals.h
index a3657f2122..785c9fade9 100644
--- a/src/nvim/globals.h
+++ b/src/nvim/globals.h
@@ -97,6 +97,34 @@ typedef enum {
 EXTERN long Rows INIT(= DFLT_ROWS);     // nr of rows in the screen
 EXTERN long Columns INIT(= DFLT_COLS);  // nr of columns in the screen
 
+// We use 64-bit file functions here, if available.  E.g. ftello() returns
+// off_t instead of long, which helps if long is 32 bit and off_t is 64 bit.
+// We assume that when fseeko() is available then ftello() is too.
+// Note that Windows has different function names.
+#if (defined(_MSC_VER) && (_MSC_VER >= 1300)) || defined(__MINGW32__)
+typedef __int64 off_T;
+# ifdef __MINGW32__
+#  define vim_lseek lseek64
+#  define vim_fseek fseeko64
+#  define vim_ftell ftello64
+# else
+#  define vim_lseek _lseeki64
+#  define vim_fseek _fseeki64
+#  define vim_ftell _ftelli64
+# endif
+#else
+typedef off_t off_T;
+# ifdef HAVE_FSEEKO
+#  define vim_lseek lseek
+#  define vim_ftell ftello
+#  define vim_fseek fseeko
+# else
+#  define vim_lseek lseek
+#  define vim_ftell ftell
+#  define vim_fseek(a, b, c) fseek(a, (long)b, c)
+# endif
+#endif
+
 /*
  * The characters and attributes cached for the screen.
  */
@@ -987,7 +1015,7 @@ EXTERN int did_cursorhold INIT(= false);       // set when CursorHold t'gerd
 // for CursorMoved event
 EXTERN pos_T last_cursormoved INIT(= INIT_POS_T(0, 0, 0));
 
-EXTERN int last_changedtick INIT(= 0);  // for TextChanged event
+EXTERN varnumber_T last_changedtick INIT(= 0);  // for TextChanged event
 EXTERN buf_T    *last_changedtick_buf INIT(= NULL);
 
 EXTERN int postponed_split INIT(= 0);       /* for CTRL-W CTRL-] command */
diff --git a/src/nvim/indent.c b/src/nvim/indent.c
index 5471b41b2c..efca739c2d 100644
--- a/src/nvim/indent.c
+++ b/src/nvim/indent.c
@@ -471,7 +471,7 @@ int get_breakindent_win(win_T *wp, char_u *line) {
       || prev_tick != wp->w_buffer->b_changedtick) {
     prev_line = line;
     prev_ts = wp->w_buffer->b_p_ts;
-    prev_tick = wp->w_buffer->b_changedtick;
+    prev_tick = (int)wp->w_buffer->b_changedtick;
     prev_indent = get_indent_str(line,
             (int)wp->w_buffer->b_p_ts, wp->w_p_list);
   }
@@ -538,7 +538,7 @@ int get_expr_indent(void)
     sandbox++;
   }
   textlock++;
-  indent = eval_to_number(curbuf->b_p_inde);
+  indent = (int)eval_to_number(curbuf->b_p_inde);
 
   if (use_sandbox) {
     sandbox--;
diff --git a/src/nvim/keymap.c b/src/nvim/keymap.c
index 9c5fe78c7c..ee67b4c19d 100644
--- a/src/nvim/keymap.c
+++ b/src/nvim/keymap.c
@@ -557,7 +557,7 @@ int find_special_key(const char_u **srcp, const size_t src_len, int *const modp,
   int modifiers;
   int bit;
   int key;
-  unsigned long n;
+  uvarnumber_T n;
   int l;
 
   if (src_len == 0) {
diff --git a/src/nvim/memfile.c b/src/nvim/memfile.c
index 1abc69727c..9429703620 100644
--- a/src/nvim/memfile.c
+++ b/src/nvim/memfile.c
@@ -115,18 +115,18 @@ memfile_T *mf_open(char_u *fname, int flags)
     }
   }
 
-  off_t size;
+  off_T size;
 
   // When recovering, the actual block size will be retrieved from block 0
   // in ml_recover(). The size used here may be wrong, therefore mf_blocknr_max
   // must be rounded up.
   if (mfp->mf_fd < 0
       || (flags & (O_TRUNC|O_EXCL))
-      || (size = lseek(mfp->mf_fd, (off_t)0L, SEEK_END)) <= 0) {
+      || (size = vim_lseek(mfp->mf_fd, 0L, SEEK_END)) <= 0) {
     // no file or empty file
     mfp->mf_blocknr_max = 0;
   } else {
-    assert(sizeof(off_t) <= sizeof(blocknr_T)
+    assert(sizeof(off_T) <= sizeof(blocknr_T)
            && mfp->mf_page_size > 0
            && mfp->mf_page_size - 1 <= INT64_MAX - size);
     mfp->mf_blocknr_max = (((blocknr_T)size + mfp->mf_page_size - 1)
@@ -689,9 +689,9 @@ static int mf_read(memfile_T *mfp, bhdr_T *hp)
     return FAIL;
 
   unsigned page_size = mfp->mf_page_size;
-  // TODO(elmart): Check (page_size * hp->bh_bnum) within off_t bounds.
-  off_t offset = (off_t)(page_size * hp->bh_bnum);
-  if (lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
+  // TODO(elmart): Check (page_size * hp->bh_bnum) within off_T bounds.
+  off_T offset = (off_T)(page_size * hp->bh_bnum);
+  if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
     PERROR(_("E294: Seek error in swap file read"));
     return FAIL;
   }
@@ -716,7 +716,7 @@ static int mf_read(memfile_T *mfp, bhdr_T *hp)
 ///                - Write error in swap file.
 static int mf_write(memfile_T *mfp, bhdr_T *hp)
 {
-  off_t offset;             // offset in the file
+  off_T offset;             // offset in the file
   blocknr_T nr;             // block nr which is being written
   bhdr_T *hp2;
   unsigned page_size;       // number of bytes in a page
@@ -745,9 +745,9 @@ static int mf_write(memfile_T *mfp, bhdr_T *hp)
       hp2 = hp;
     }
 
-    // TODO(elmart): Check (page_size * nr) within off_t bounds.
-    offset = (off_t)(page_size * nr);
-    if (lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
+    // TODO(elmart): Check (page_size * nr) within off_T bounds.
+    offset = (off_T)(page_size * nr);
+    if (vim_lseek(mfp->mf_fd, offset, SEEK_SET) != offset) {
       PERROR(_("E296: Seek error in swap file write"));
       return FAIL;
     }
diff --git a/src/nvim/memline.c b/src/nvim/memline.c
index 40a6761225..55e7e01825 100644
--- a/src/nvim/memline.c
+++ b/src/nvim/memline.c
@@ -763,7 +763,7 @@ void ml_recover(void)
   int idx;
   int top;
   int txt_start;
-  off_t size;
+  off_T size;
   int called_from_main;
   int serious_error = TRUE;
   long mtime;
@@ -914,10 +914,11 @@ void ml_recover(void)
       msg_end();
       goto theend;
     }
-    if ((size = lseek(mfp->mf_fd, (off_t)0L, SEEK_END)) <= 0)
-      mfp->mf_blocknr_max = 0;              /* no file or empty file */
-    else
+    if ((size = vim_lseek(mfp->mf_fd, (off_T)0L, SEEK_END)) <= 0) {
+      mfp->mf_blocknr_max = 0;              // no file or empty file
+    } else {
       mfp->mf_blocknr_max = size / mfp->mf_page_size;
+    }
     mfp->mf_infile_count = mfp->mf_blocknr_max;
 
     /* need to reallocate the memory used to store the data */
diff --git a/src/nvim/ops.c b/src/nvim/ops.c
index e374686286..c5660f68fd 100644
--- a/src/nvim/ops.c
+++ b/src/nvim/ops.c
@@ -938,13 +938,11 @@ static int stuff_yank(int regname, char_u *p)
 
 static int execreg_lastc = NUL;
 
-/*
- * execute a yank register: copy it into the stuff buffer
- *
- * return FAIL for failure, OK otherwise
- */
-int 
-do_execreg (
+/// Execute a yank register: copy it into the stuff buffer
+///
+/// Return FAIL for failure, OK otherwise
+int
+do_execreg(
     int regname,
     int colon,                      /* insert ':' before each line */
     int addcr,                      /* always add '\n' to end of line */
@@ -4439,8 +4437,8 @@ int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
   char_u buf2[NUMBUFLEN];
   int pre;  // 'X' or 'x': hex; '0': octal; 'B' or 'b': bin
   static bool hexupper = false;  // 0xABC
-  unsigned long n;
-  unsigned long oldn;
+  uvarnumber_T n;
+  uvarnumber_T oldn;
   char_u      *ptr;
   int c;
   int todel;
@@ -4635,20 +4633,20 @@ int do_addsub(int op_type, pos_T *pos, int length, linenr_T Prenum1)
 
     oldn = n;
 
-    n = subtract ? n - (unsigned long) Prenum1
-                 : n + (unsigned long) Prenum1;
+    n = subtract ? n - (uvarnumber_T)Prenum1
+                 : n + (uvarnumber_T)Prenum1;
 
     // handle wraparound for decimal numbers
     if (!pre) {
       if (subtract) {
         if (n > oldn) {
-          n = 1 + (n ^ (unsigned long)-1);
+          n = 1 + (n ^ (uvarnumber_T)-1);
           negative ^= true;
         }
       } else {
         // add
         if (n < oldn) {
-          n = (n ^ (unsigned long)-1);
+          n = (n ^ (uvarnumber_T)-1);
           negative ^= true;
         }
       }
@@ -5238,11 +5236,13 @@ void clear_oparg(oparg_T *oap)
  *  case, eol_size will be added to the character count to account for
  *  the size of the EOL character.
  */
-static long line_count_info(char_u *line, long *wc, long *cc, long limit, int eol_size)
+static varnumber_T line_count_info(char_u *line, varnumber_T *wc,
+                                   varnumber_T *cc, varnumber_T limit,
+                                   int eol_size)
 {
-  long i;
-  long words = 0;
-  long chars = 0;
+  varnumber_T i;
+  varnumber_T words = 0;
+  varnumber_T chars = 0;
   int is_word = 0;
 
   for (i = 0; i < limit && line[i] != NUL; ) {
@@ -5280,15 +5280,15 @@ void cursor_pos_info(dict_T *dict)
   char_u buf1[50];
   char_u buf2[40];
   linenr_T lnum;
-  long byte_count = 0;
-  long bom_count = 0;
-  long byte_count_cursor = 0;
-  long char_count = 0;
-  long char_count_cursor = 0;
-  long word_count = 0;
-  long word_count_cursor = 0;
+  varnumber_T byte_count = 0;
+  varnumber_T bom_count = 0;
+  varnumber_T byte_count_cursor = 0;
+  varnumber_T char_count = 0;
+  varnumber_T char_count_cursor = 0;
+  varnumber_T word_count = 0;
+  varnumber_T word_count_cursor = 0;
   int eol_size;
-  long last_check = 100000L;
+  varnumber_T last_check = 100000L;
   long line_count_selected = 0;
   pos_T min_pos, max_pos;
   oparg_T oparg;
@@ -5395,15 +5395,16 @@ void cursor_pos_info(dict_T *dict)
         if (lnum == curwin->w_cursor.lnum) {
           word_count_cursor += word_count;
           char_count_cursor += char_count;
-          byte_count_cursor = byte_count +
-                              line_count_info(ml_get(lnum),
-              &word_count_cursor, &char_count_cursor,
-              (long)(curwin->w_cursor.col + 1), eol_size);
+          byte_count_cursor = byte_count
+            + line_count_info(ml_get(lnum), &word_count_cursor,
+                              &char_count_cursor,
+                              (varnumber_T)(curwin->w_cursor.col + 1),
+                              eol_size);
         }
       }
-      /* Add to the running totals */
-      byte_count += line_count_info(ml_get(lnum), &word_count,
-          &char_count, (long)MAXCOL, eol_size);
+      // Add to the running totals
+      byte_count += line_count_info(ml_get(lnum), &word_count, &char_count,
+                                    (varnumber_T)MAXCOL, eol_size);
     }
 
     // Correction for when last line doesn't have an EOL.
diff --git a/src/nvim/option.c b/src/nvim/option.c
index 392a2f3908..337d16a55b 100644
--- a/src/nvim/option.c
+++ b/src/nvim/option.c
@@ -1144,7 +1144,7 @@ do_set (
   int afterchar;                    /* character just after option name */
   int len;
   int i;
-  long value;
+  varnumber_T value;
   int key;
   uint32_t flags;                   /* flags for current option */
   char_u      *varp = NULL;         /* pointer to variable for current option */
@@ -1477,7 +1477,7 @@ do_set (
             if (removing) {
               value = *(long *)varp - value;
             }
-            errmsg = (char_u *)set_num_option(opt_idx, varp, value,
+            errmsg = (char_u *)set_num_option(opt_idx, varp, (long)value,
                                               errbuf, sizeof(errbuf),
                                               opt_flags);
           } else if (opt_idx >= 0) {  // String.
@@ -4630,7 +4630,7 @@ get_option_value (
     if ((int *)varp == &curbuf->b_changed) {
       *numval = curbufIsChanged();
     } else {
-      *numval = *(int *)varp;
+      *numval = (long) *(int *)varp;  // NOLINT(whitespace/cast)
     }
   }
   return 1;
diff --git a/src/nvim/quickfix.c b/src/nvim/quickfix.c
index ff51bf289e..b6878cbbf4 100644
--- a/src/nvim/quickfix.c
+++ b/src/nvim/quickfix.c
@@ -4027,7 +4027,7 @@ int get_errorlist_properties(win_T *wp, dict_T *what, dict_T *retdict)
   if ((di = tv_dict_find(what, S_LEN("nr"))) != NULL) {
     // Use the specified quickfix/location list
     if (di->di_tv.v_type == VAR_NUMBER) {
-      qf_idx = di->di_tv.vval.v_number - 1;
+      qf_idx = (int)di->di_tv.vval.v_number - 1;
       if (qf_idx < 0 || qf_idx >= qi->qf_listcount) {
         return FAIL;
       }
@@ -4101,7 +4101,7 @@ static int qf_add_entries(qf_info_T *qi, list_T *list, char_u *title,
 
     char *const filename = tv_dict_get_string(d, "filename", true);
     int bufnum = (int)tv_dict_get_number(d, "bufnr");
-    long lnum = tv_dict_get_number(d, "lnum");
+    long lnum = (long)tv_dict_get_number(d, "lnum");
     int col = (int)tv_dict_get_number(d, "col");
     char_u vcol = (char_u)tv_dict_get_number(d, "vcol");
     int nr = (int)tv_dict_get_number(d, "nr");
@@ -4183,7 +4183,7 @@ static int qf_set_properties(qf_info_T *qi, dict_T *what, int action)
   if ((di = tv_dict_find(what, S_LEN("nr"))) != NULL) {
     // Use the specified quickfix/location list
     if (di->di_tv.v_type == VAR_NUMBER) {
-      qf_idx = di->di_tv.vval.v_number - 1;
+      qf_idx = (int)di->di_tv.vval.v_number - 1;
       if (qf_idx < 0 || qf_idx >= qi->qf_listcount) {
         return FAIL;
       }
diff --git a/src/nvim/strings.c b/src/nvim/strings.c
index c5fd8741b8..687f734742 100644
--- a/src/nvim/strings.c
+++ b/src/nvim/strings.c
@@ -653,7 +653,7 @@ static float_T tv_float(typval_T *const tvs, int *const idxp)
     if (tvs[idx].v_type == VAR_FLOAT) {
       f = tvs[idx].vval.v_float;
     } else if (tvs[idx].v_type == VAR_NUMBER) {
-      f = tvs[idx].vval.v_number;
+      f = (float_T)tvs[idx].vval.v_number;
     } else {
       EMSG(_("E807: Expected Float argument for printf()"));
     }
@@ -910,6 +910,13 @@ int vim_vsnprintf(char *str, size_t str_m, const char *fmt, va_list ap,
         default: break;
       }
 
+      switch (fmt_spec) {
+        case 'd': case 'u': case 'o': case 'x': case 'X':
+          if (tvs && length_modifier == '\0') {
+            length_modifier = '2';
+          }
+      }
+
       // get parameter value, do initial processing
       switch (fmt_spec) {
         // '%' and 'c' behave similar to 's' regarding flags and field widths
diff --git a/src/nvim/tag.c b/src/nvim/tag.c
index 88b45add54..be9d621c7d 100644
--- a/src/nvim/tag.c
+++ b/src/nvim/tag.c
@@ -105,15 +105,6 @@ static char_u *topmsg = (char_u *)N_("E556: at top of tag stack");
 
 static char_u   *tagmatchname = NULL;   /* name of last used tag */
 
-/*
- * We use ftello() here, if available.  It returns off_t instead of long,
- * which helps if long is 32 bit and off_t is 64 bit.
- * We assume that when fseeko() is available then ftello() is too.
- */
-#ifdef HAVE_FSEEKO
-# define ftell ftello
-#endif
-
 /*
  * Tag for preview window is remembered separately, to avoid messing up the
  * normal tagstack.
@@ -1088,22 +1079,21 @@ find_tags (
   char_u      *p;
   char_u      *s;
   int i;
-  int tag_file_sorted = NUL;            /* !_TAG_FILE_SORTED value */
-  struct tag_search_info        /* Binary search file offsets */
-  {
-    off_t low_offset;           /* offset for first char of first line that
-                                   could match */
-    off_t high_offset;          /* offset of char after last line that could
-                                   match */
-    off_t curr_offset;          /* Current file offset in search range */
-    off_t curr_offset_used;       /* curr_offset used when skipping back */
-    off_t match_offset;         /* Where the binary search found a tag */
-    int low_char;               /* first char at low_offset */
-    int high_char;              /* first char at high_offset */
+  int tag_file_sorted = NUL;            // !_TAG_FILE_SORTED value
+  struct tag_search_info {      // Binary search file offsets
+    off_T low_offset;           // offset for first char of first line that
+                                // could match
+    off_T high_offset;          // offset of char after last line that could
+                                // match
+    off_T curr_offset;          // Current file offset in search range
+    off_T curr_offset_used;     // curr_offset used when skipping back
+    off_T match_offset;         // Where the binary search found a tag
+    int low_char;               // first char at low_offset
+    int high_char;              // first char at high_offset
   } search_info;
-  off_t filesize;
+  off_T filesize;
   int tagcmp;
-  off_t offset;
+  off_T offset;
   int round;
   enum {
     TS_START,                   /* at start of file */
@@ -1378,36 +1368,28 @@ find_tags (
         if (state == TS_BINARY || state == TS_SKIP_BACK) {
           /* Adjust the search file offset to the correct position */
           search_info.curr_offset_used = search_info.curr_offset;
-#ifdef HAVE_FSEEKO
-          fseeko(fp, search_info.curr_offset, SEEK_SET);
-#else
-          fseek(fp, (long)search_info.curr_offset, SEEK_SET);
-#endif
+          vim_fseek(fp, search_info.curr_offset, SEEK_SET);
           eof = vim_fgets(lbuf, LSIZE, fp);
           if (!eof && search_info.curr_offset != 0) {
             /* The explicit cast is to work around a bug in gcc 3.4.2
              * (repeated below). */
-            search_info.curr_offset = ftell(fp);
+            search_info.curr_offset = vim_ftell(fp);
             if (search_info.curr_offset == search_info.high_offset) {
-              /* oops, gone a bit too far; try from low offset */
-#ifdef HAVE_FSEEKO
-              fseeko(fp, search_info.low_offset, SEEK_SET);
-#else
-              fseek(fp, (long)search_info.low_offset, SEEK_SET);
-#endif
+              // oops, gone a bit too far; try from low offset
+              vim_fseek(fp, search_info.low_offset, SEEK_SET);
               search_info.curr_offset = search_info.low_offset;
             }
             eof = vim_fgets(lbuf, LSIZE, fp);
           }
           /* skip empty and blank lines */
           while (!eof && vim_isblankline(lbuf)) {
-            search_info.curr_offset = ftell(fp);
+            search_info.curr_offset = vim_ftell(fp);
             eof = vim_fgets(lbuf, LSIZE, fp);
           }
           if (eof) {
             /* Hit end of file.  Skip backwards. */
             state = TS_SKIP_BACK;
-            search_info.match_offset = ftell(fp);
+            search_info.match_offset = vim_ftell(fp);
             search_info.curr_offset = search_info.curr_offset_used;
             continue;
           }
@@ -1523,10 +1505,10 @@ line_read_in:
            */
           if (state == TS_BINARY) {
             // Get the tag file size.
-            if ((filesize = lseek(fileno(fp), (off_t)0L, SEEK_END)) <= 0) {
+            if ((filesize = vim_lseek(fileno(fp), (off_T)0L, SEEK_END)) <= 0) {
               state = TS_LINEAR;
             } else {
-              lseek(fileno(fp), (off_t)0L, SEEK_SET);
+              vim_lseek(fileno(fp), (off_T)0L, SEEK_SET);
 
               /* Calculate the first read offset in the file.  Start
                * the search in the middle of the file. */
@@ -1564,11 +1546,7 @@ parse_line:
                 /* Avoid getting stuck. */
                 linear = TRUE;
                 state = TS_LINEAR;
-# ifdef HAVE_FSEEKO
-                fseeko(fp, search_info.low_offset, SEEK_SET);
-# else
-                fseek(fp, (long)search_info.low_offset, SEEK_SET);
-# endif
+                vim_fseek(fp, search_info.low_offset, SEEK_SET);
               }
               continue;
             }
@@ -1647,7 +1625,7 @@ parse_line:
               continue;
             }
             if (tagcmp < 0) {
-              search_info.curr_offset = ftell(fp);
+              search_info.curr_offset = vim_ftell(fp);
               if (search_info.curr_offset < search_info.high_offset) {
                 search_info.low_offset = search_info.curr_offset;
                 if (sortic)
@@ -1683,10 +1661,11 @@ parse_line:
           } else if (state == TS_STEP_FORWARD)   {
             assert(cmplen >= 0);
             if (mb_strnicmp(tagp.tagname, orgpat.head, (size_t)cmplen) != 0) {
-              if ((off_t)ftell(fp) > search_info.match_offset)
-                break;                  /* past last match */
-              else
-                continue;               /* before first match */
+              if ((off_T)vim_ftell(fp) > search_info.match_offset) {
+                break;                  // past last match
+              } else {
+                continue;               // before first match
+              }
             }
           } else
           /* skip this match if it can't match */
@@ -1907,10 +1886,11 @@ parse_line:
 
       if (line_error) {
         EMSG2(_("E431: Format error in tags file \"%s\""), tag_fname);
-        if (!use_cscope)
-          EMSGN(_("Before byte %" PRId64), ftell(fp));
-        stop_searching = TRUE;
-        line_error = FALSE;
+        if (!use_cscope) {
+          EMSGN(_("Before byte %" PRId64), vim_ftell(fp));
+        }
+        stop_searching = true;
+        line_error = false;
       }
 
       if (!use_cscope)
diff --git a/src/nvim/testdir/Makefile b/src/nvim/testdir/Makefile
index 5b0d826c75..3482001f63 100644
--- a/src/nvim/testdir/Makefile
+++ b/src/nvim/testdir/Makefile
@@ -60,6 +60,7 @@ NEW_TESTS ?= \
 	    test_quickfix.res \
 	    test_signs.res \
 	    test_smartindent.res \
+	    test_stat.res \
 	    test_substitute.res \
 	    test_syntax.res \
 	    test_tabpage.res \
diff --git a/src/nvim/testdir/test_expr.vim b/src/nvim/testdir/test_expr.vim
index ce1523324e..82c5d21bd0 100644
--- a/src/nvim/testdir/test_expr.vim
+++ b/src/nvim/testdir/test_expr.vim
@@ -98,6 +98,35 @@ func Test_special_char()
   call assert_fails('echo "\<C-">')
 endfunc
 
+func Test_option_value()
+  " boolean
+  set bri
+  call assert_equal(1, &bri)
+  set nobri
+  call assert_equal(0, &bri)
+
+  " number
+  set ts=1
+  call assert_equal(1, &ts)
+  set ts=8
+  call assert_equal(8, &ts)
+
+  " string
+  exe "set cedit=\<Esc>"
+  call assert_equal("\<Esc>", &cedit)
+  set cpo=
+  call assert_equal("", &cpo)
+  set cpo=abcdefi
+  call assert_equal("abcdefi", &cpo)
+  set cpo&vim
+endfunc
+
+function Test_printf_64bit()
+  if has('num64')
+    call assert_equal("123456789012345", printf('%d', 123456789012345))
+  endif
+endfunc
+
 func Test_setmatches()
   hi def link 1 Comment
   hi def link 2 PreProc
diff --git a/src/nvim/testdir/test_float_func.vim b/src/nvim/testdir/test_float_func.vim
index 07ffe96129..5ea5192994 100644
--- a/src/nvim/testdir/test_float_func.vim
+++ b/src/nvim/testdir/test_float_func.vim
@@ -224,6 +224,20 @@ func Test_str2float()
   call assert_fails("call str2float(function('string'))", 'E729:')
 endfunc
 
+func Test_float2nr()
+  call assert_equal(1, float2nr(1.234))
+  call assert_equal(123, float2nr(1.234e2))
+  call assert_equal(12, float2nr(123.4e-1))
+  let max_number = 1/0
+  let min_number = -max_number
+  call assert_equal(max_number/2+1, float2nr(pow(2, 62)))
+  call assert_equal(max_number, float2nr(pow(2, 63)))
+  call assert_equal(max_number, float2nr(pow(2, 64)))
+  call assert_equal(min_number/2-1, float2nr(-pow(2, 62)))
+  call assert_equal(min_number, float2nr(-pow(2, 63)))
+  call assert_equal(min_number, float2nr(-pow(2, 64)))
+endfunc
+
 func Test_floor()
   call assert_equal('2.0', string(floor(2.0)))
   call assert_equal('2.0', string(floor(2.11)))
@@ -283,3 +297,36 @@ func Test_isnan()
   call assert_equal(0, isnan([]))
   call assert_equal(0, isnan({}))
 endfunc
+
+" This was converted from test65
+func Test_float_misc()
+  call assert_equal('123.456000', printf('%f', 123.456))
+  call assert_equal('1.234560e+02', printf('%e', 123.456))
+  call assert_equal('123.456', printf('%g', 123.456))
+  " +=
+  let v = 1.234
+  let v += 6.543
+  call assert_equal('7.777', printf('%g', v))
+  let v = 1.234
+  let v += 5
+  call assert_equal('6.234', printf('%g', v))
+  let v = 5
+  let v += 3.333
+  call assert_equal('8.333', string(v))
+  " ==
+  let v = 1.234
+  call assert_true(v == 1.234)
+  call assert_false(v == 1.2341)
+  " add-subtract
+  call assert_equal('5.234', printf('%g', 4 + 1.234))
+  call assert_equal('-6.766', printf('%g', 1.234 - 8))
+  " mult-div
+  call assert_equal('4.936', printf('%g', 4 * 1.234))
+  call assert_equal('0.003241', printf('%g', 4.0 / 1234))
+  " dict
+  call assert_equal("{'x': 1.234, 'y': -2.0e20}", string({'x': 1.234, 'y': -2.0e20}))
+  " list
+  call assert_equal('[-123.4, 2.0e-20]', string([-123.4, 2.0e-20]))
+endfunc
+
+" vim: shiftwidth=2 sts=2 expandtab
diff --git a/src/nvim/testdir/test_largefile.vim b/src/nvim/testdir/test_largefile.vim
new file mode 100644
index 0000000000..1b3e02a0c8
--- /dev/null
+++ b/src/nvim/testdir/test_largefile.vim
@@ -0,0 +1,34 @@
+" Tests for large files
+" This is only executed manually: "make test_largefile".
+" This is not run as part of "make test".
+
+func Test_largefile()
+  let fname = 'Xlarge.txt'
+
+  call delete(fname)
+  exe "e" fname
+  " Make sure that a line break is 1 byte (LF).
+  set ff=unix
+  set undolevels=-1
+  " Input 99 'A's. The line becomes 100 bytes including a line break.
+  exe "normal 99iA\<Esc>"
+  yank
+  " Put 39,999,999 times. The file becomes 4,000,000,000 bytes.
+  normal 39999999p
+  " Moving around in the file randomly.
+  normal G
+  normal 10%
+  normal 90%
+  normal 50%
+  normal gg
+  w
+  " Check if the file size is 4,000,000,000 bytes.
+  let fsize=getfsize(fname)
+  if has('num64')
+    call assert_true(fsize == 4000000000)
+  else
+    " getfsize() returns -2 if a Number is 32 bits.
+    call assert_true(fsize == -2)
+  endif
+  call delete(fname)
+endfunc
diff --git a/src/nvim/testdir/test_stat.vim b/src/nvim/testdir/test_stat.vim
new file mode 100644
index 0000000000..89ca9ef379
--- /dev/null
+++ b/src/nvim/testdir/test_stat.vim
@@ -0,0 +1,64 @@
+" Tests for stat functions and checktime
+
+func Test_existent_file()
+  let fname='Xtest.tmp'
+
+  let ts=localtime()
+  sleep 1
+  let fl=['Hello World!']
+  call writefile(fl, fname)
+  let tf=getftime(fname)
+  sleep 1
+  let te=localtime()
+
+  call assert_true(ts <= tf && tf <= te)
+  call assert_equal(strlen(fl[0] . "\n"), getfsize(fname))
+  call assert_equal('file', getftype(fname))
+  call assert_equal('rw-', getfperm(fname)[0:2])
+endfunc
+
+func Test_existent_directory()
+  let dname='.'
+
+  call assert_equal(0, getfsize(dname))
+  call assert_equal('dir', getftype(dname))
+  call assert_equal('rwx', getfperm(dname)[0:2])
+endfunc
+
+func Test_checktime()
+  let fname='Xtest.tmp'
+
+  let fl=['Hello World!']
+  call writefile(fl, fname)
+  set autoread
+  exec 'e' fname
+  sleep 2
+  let fl=readfile(fname)
+  let fl[0] .= ' - checktime'
+  call writefile(fl, fname)
+  checktime
+  call assert_equal(fl[0], getline(1))
+endfunc
+
+func Test_nonexistent_file()
+  let fname='Xtest.tmp'
+
+  call delete(fname)
+  call assert_equal(-1, getftime(fname))
+  call assert_equal(-1, getfsize(fname))
+  call assert_equal('', getftype(fname))
+  call assert_equal('', getfperm(fname))
+endfunc
+
+func Test_win32_symlink_dir()
+  " On Windows, non-admin users cannot create symlinks.
+  " So we use an existing symlink for this test.
+  if has('win32')
+    " Check if 'C:\Users\All Users' is a symlink to a directory.
+    let res=system('dir C:\Users /a')
+    if match(res, '\C<SYMLINKD> *All Users') >= 0
+      " Get the filetype of the symlink.
+      call assert_equal('dir', getftype('C:\Users\All Users'))
+    endif
+  endif
+endfunc
diff --git a/src/nvim/testdir/test_vimscript.vim b/src/nvim/testdir/test_vimscript.vim
index da3adf5e2b..4e0f1bbd2f 100644
--- a/src/nvim/testdir/test_vimscript.vim
+++ b/src/nvim/testdir/test_vimscript.vim
@@ -1062,6 +1062,32 @@ func Test_echo_and_string()
     call assert_equal(["{'a': [], 'b': []}",
 		     \ "{'a': [], 'b': []}"], l)
 
+"-------------------------------------------------------------------------------
+" Test 94:  64-bit Numbers					    {{{1
+"-------------------------------------------------------------------------------
+
+func Test_num64()
+    if !has('num64')
+	return
+    endif
+
+    call assert_notequal( 4294967296, 0)
+    call assert_notequal(-4294967296, 0)
+    call assert_equal( 4294967296,  0xFFFFffff + 1)
+    call assert_equal(-4294967296, -0xFFFFffff - 1)
+
+    call assert_equal( 9223372036854775807,  1 / 0)
+    call assert_equal(-9223372036854775807, -1 / 0)
+    call assert_equal(-9223372036854775807 - 1,  0 / 0)
+
+    call assert_equal( 0x7FFFffffFFFFffff, float2nr( 1.0e150))
+    call assert_equal(-0x7FFFffffFFFFffff, float2nr(-1.0e150))
+
+    let rng = range(0xFFFFffff, 0x100000001)
+    call assert_equal([0xFFFFffff, 0x100000000, 0x100000001], rng)
+    call assert_equal(0x100000001, max(rng))
+    call assert_equal(0xFFFFffff, min(rng))
+    call assert_equal(rng, sort(range(0x100000001, 0xFFFFffff, -1), 'N'))
 endfunc
 
 "-------------------------------------------------------------------------------
@@ -1146,6 +1172,49 @@ func Test_script_emty_line_continuation()
     \
 endfunc
 
+"-------------------------------------------------------------------------------
+" Test 97:  bitwise functions						    {{{1
+"-------------------------------------------------------------------------------
+func Test_bitwise_functions()
+    " and
+    call assert_equal(127, and(127, 127))
+    call assert_equal(16, and(127, 16))
+    call assert_equal(0, and(127, 128))
+    call assert_fails("call and(1.0, 1)", 'E805:')
+    call assert_fails("call and([], 1)", 'E745:')
+    call assert_fails("call and({}, 1)", 'E728:')
+    call assert_fails("call and(1, 1.0)", 'E805:')
+    call assert_fails("call and(1, [])", 'E745:')
+    call assert_fails("call and(1, {})", 'E728:')
+    " or
+    call assert_equal(23, or(16, 7))
+    call assert_equal(15, or(8, 7))
+    call assert_equal(123, or(0, 123))
+    call assert_fails("call or(1.0, 1)", 'E805:')
+    call assert_fails("call or([], 1)", 'E745:')
+    call assert_fails("call or({}, 1)", 'E728:')
+    call assert_fails("call or(1, 1.0)", 'E805:')
+    call assert_fails("call or(1, [])", 'E745:')
+    call assert_fails("call or(1, {})", 'E728:')
+    " xor
+    call assert_equal(0, xor(127, 127))
+    call assert_equal(111, xor(127, 16))
+    call assert_equal(255, xor(127, 128))
+    call assert_fails("call xor(1.0, 1)", 'E805:')
+    call assert_fails("call xor([], 1)", 'E745:')
+    call assert_fails("call xor({}, 1)", 'E728:')
+    call assert_fails("call xor(1, 1.0)", 'E805:')
+    call assert_fails("call xor(1, [])", 'E745:')
+    call assert_fails("call xor(1, {})", 'E728:')
+    " invert
+    call assert_equal(65408, and(invert(127), 65535))
+    call assert_equal(65519, and(invert(16), 65535))
+    call assert_equal(65407, and(invert(128), 65535))
+    call assert_fails("call invert(1.0)", 'E805:')
+    call assert_fails("call invert([])", 'E745:')
+    call assert_fails("call invert({})", 'E728:')
+endfunc
+
 "-------------------------------------------------------------------------------
 " Modelines								    {{{1
 " vim: ts=8 sw=4 tw=80 fdm=marker
diff --git a/src/nvim/version.c b/src/nvim/version.c
index b579cdef12..804968af3d 100644
--- a/src/nvim/version.c
+++ b/src/nvim/version.c
@@ -220,7 +220,7 @@ static const int included_patches[] = {
   2227,
   2226,
   2225,
-  // 2224,
+  2224,
   2223,
   2222,
   2221,
@@ -415,7 +415,7 @@ static const int included_patches[] = {
   // 2032 NA
   2031,
   // 2030 NA
-  // 2029,
+  2029,
   2028,
   // 2027 NA
   // 2026 NA
@@ -458,18 +458,18 @@ static const int included_patches[] = {
   1989,
   // 1988 NA
   // 1987 NA
-  // 1986,
+  1986,
   // 1985 NA
   1984,
   // 1983 NA
   // 1982 NA
   1981,
   1980,
-  // 1979,
-  // 1978,
-  // 1977,
-  // 1976,
-  // 1975,
+  1979,
+  1978,
+  1977,
+  1976,
+  1975,
   // 1974 NA
   1973,
   // 1972 NA
diff --git a/test/functional/eval/msgpack_functions_spec.lua b/test/functional/eval/msgpack_functions_spec.lua
index 4a052b4aff..b241635dfe 100644
--- a/test/functional/eval/msgpack_functions_spec.lua
+++ b/test/functional/eval/msgpack_functions_spec.lua
@@ -337,7 +337,8 @@ describe('msgpack*() functions', function()
     eq(1, eval('type(parsed[0]) == type(0) ' ..
                '|| parsed[0]._TYPE is v:msgpack_types.integer'))
     if eval('type(parsed[0]) == type(0)') == 1 then
-      eq(1, eval('0xFFFFFFFFFFFFFFFF == parsed[0]'))
+      command('call assert_equal(0xFFFFFFFFFFFFFFFF, parsed[0])')
+      eq({}, eval('v:errors'))
     else
       eq({_TYPE={}, _VAL={1, 3, 0x7FFFFFFF, 0x7FFFFFFF}}, eval('parsed[0]'))
     end
@@ -351,7 +352,8 @@ describe('msgpack*() functions', function()
     eq(1, eval('type(parsed[0]) == type(0) ' ..
                '|| parsed[0]._TYPE is v:msgpack_types.integer'))
     if eval('type(parsed[0]) == type(0)') == 1 then
-      eq(1, eval('-0x8000000000000000 == parsed[0]'))
+      command('call assert_equal(-0x7fffffffffffffff - 1, parsed[0])')
+      eq({}, eval('v:errors'))
     else
       eq({_TYPE={}, _VAL={-1, 2, 0, 0}}, eval('parsed[0]'))
     end