Introduce os_localtime_r() and os_get_local_time()

Replace localtime() with os_localtime_r() in `eval.c` and `undo.c`.

src/eval.c

@@ -65,6 +65,7 @@
 #include "os/job.h"
 #include "os/rstream.h"
 #include "os/rstream_defs.h"
+#include "os/time.h"
 
 #if defined(FEAT_FLOAT)
 # include <math.h>
@@ -14163,7 +14164,6 @@ static void f_str2nr(typval_T *argvars, typval_T *rettv)
 static void f_strftime(typval_T *argvars, typval_T *rettv)
 {
   char_u result_buf[256];
-  struct tm   *curtime;
   time_t seconds;
   char_u      *p;
 
@@ -14174,9 +14174,11 @@ static void f_strftime(typval_T *argvars, typval_T *rettv)
     seconds = time(NULL);
   else
     seconds = (time_t)get_tv_number(&argvars[1]);
-  curtime = localtime(&seconds);
+
+  struct tm curtime;
+  struct tm *curtime_ptr = os_localtime_r(&seconds, &curtime);
   /* MSVC returns NULL for an invalid value of seconds. */
-  if (curtime == NULL)
+  if (curtime_ptr == NULL)
     rettv->vval.v_string = vim_strsave((char_u *)_("(Invalid)"));
   else {
     vimconv_T conv;
@@ -14189,7 +14191,7 @@ static void f_strftime(typval_T *argvars, typval_T *rettv)
       p = string_convert(&conv, p, NULL);
     if (p != NULL)
       (void)strftime((char *)result_buf, sizeof(result_buf),
-          (char *)p, curtime);
+          (char *)p, curtime_ptr);
     else
       result_buf[0] = NUL;
 

src/log.c

@@ -11,6 +11,7 @@
 #include "misc1.h"
 #include "types.h"
 #include "os/os.h"
+#include "os/time.h"
 
 #define USR_LOG_FILE "$HOME/.nvimlog"
 
@@ -117,23 +118,13 @@ static bool v_do_log_to_file(FILE *log_file, int log_level,
   assert(log_level >= DEBUG_LOG_LEVEL && log_level <= ERROR_LOG_LEVEL);
 
   // format current timestamp in local time
-  struct timeval tv;
-  if (gettimeofday(&tv, NULL) < 0) {
+  struct tm local_time;
+  if (os_get_localtime(&local_time) == NULL) {
     return false;
   }
-#ifdef UNIX
-  // localtime() is not thread-safe. POSIX provides localtime_r() as a
-  // thread-safe version.
-  struct tm local_time_allocated;
-  struct tm *local_time = localtime_r(&tv.tv_sec, &local_time_allocated);
-#else
-  // Windows version of localtime() is thread-safe.
-  // See http://msdn.microsoft.com/en-us/library/bf12f0hc%28VS.80%29.aspx
-  struct tm *local_time = localtime(&tv.tv_sec);  // NOLINT
-#endif
   char date_time[20];
   if (strftime(date_time, sizeof(date_time), "%Y/%m/%d %H:%M:%S",
-               local_time) == 0) {
+               &local_time) == 0) {
     return false;
   }
 

src/os/time.c

@@ -1,5 +1,6 @@
 #include <stdint.h>
 #include <stdbool.h>
+#include <sys/time.h>
 
 #include <uv.h>
 
@@ -59,3 +60,27 @@ static void microdelay(uint64_t microseconds)
 
   uv_mutex_unlock(&delay_mutex);
 }
+
+struct tm *os_localtime_r(const time_t *clock, struct tm *result)
+{
+#ifdef UNIX
+  // POSIX provides localtime_r() as a thread-safe version of localtime().
+  return localtime_r(clock, result);
+#else
+  // Windows version of localtime() is thread-safe.
+  // See http://msdn.microsoft.com/en-us/library/bf12f0hc%28VS.80%29.aspx
+  struct tm *local_time = localtime(clock);  // NOLINT
+  *result = *local_time;
+return result;
+#endif
+}
+
+struct tm *os_get_localtime(struct tm *result)
+{
+  struct timeval tv;
+  if (gettimeofday(&tv, NULL) < 0) {
+    return NULL;
+  }
+
+  return os_localtime_r(&tv.tv_sec, result);
+}

src/os/time.h

@@ -19,6 +19,17 @@ void os_delay(uint64_t milliseconds, bool ignoreinput);
 /// @param ignoreinput If true, allow a SIGINT to interrupt us
 void os_microdelay(uint64_t microseconds, bool ignoreinput);
 
+/// Portable version of POSIX localtime_r()
+///
+/// @return NULL in case of error
+struct tm *os_localtime_r(const time_t *clock, struct tm *result);
+
+/// Obtains the current UNIX timestamp and adjusts it to local time
+///
+/// @param result Pointer to a 'struct tm' where the result should be placed
+/// @return A pointer to a 'struct tm' in the current time zone (the 'result'
+///         argument) or NULL in case of error
+struct tm *os_get_localtime(struct tm *result);
 
 #endif  // NEOVIM_OS_TIME_H
 

src/undo.c

@@ -103,6 +103,7 @@
 #include "screen.h"
 #include "sha256.h"
 #include "os/os.h"
+#include "os/time.h"
 
 static long get_undolevel(void);
 static void u_unch_branch(u_header_T *uhp);
@@ -2455,16 +2456,16 @@ void ex_undolist(exarg_T *eap)
  */
 static void u_add_time(char_u *buf, size_t buflen, time_t tt)
 {
-  struct tm   *curtime;
+  struct tm curtime;
 
   if (time(NULL) - tt >= 100) {
-    curtime = localtime(&tt);
+    os_localtime_r(&tt, &curtime);
     if (time(NULL) - tt < (60L * 60L * 12L))
       /* within 12 hours */
-      (void)strftime((char *)buf, buflen, "%H:%M:%S", curtime);
+      (void)strftime((char *)buf, buflen, "%H:%M:%S", &curtime);
     else
       /* longer ago */
-      (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", curtime);
+      (void)strftime((char *)buf, buflen, "%Y/%m/%d %H:%M:%S", &curtime);
   } else
   vim_snprintf((char *)buf, buflen, _("%" PRId64 " seconds ago"),
       (int64_t)(time(NULL) - tt));