utils: Make TimevalToString thread-safe

src/zm_utils.cpp

@@ -22,7 +22,7 @@
 #include "zm_config.h"
 #include "zm_logger.h"
 #include <algorithm>
-#include <cstdarg>
+#include <array>
 #include <cstring>
 #include <fcntl.h> /* Definition of AT_* constants */
 #include <sstream>
@@ -328,16 +328,17 @@ void timespec_diff(struct timespec *start, struct timespec *end, struct timespec
   }
 }
 
-char *timeval_to_string( struct timeval tv ) {
-  time_t nowtime;
-  struct tm *nowtm;
-  static char tmbuf[20], buf[28];
+std::string TimevalToString(timeval tv) {
+  tm now = {};
+  std::array<char, 26> tm_buf = {};
 
-  nowtime = tv.tv_sec;
-  nowtm = localtime(&nowtime);
-  strftime(tmbuf, sizeof tmbuf, "%Y-%m-%d %H:%M:%S", nowtm);
-  snprintf(buf, sizeof buf-1, "%s.%06ld", tmbuf, tv.tv_usec);
-  return buf;
+  localtime_r(&tv.tv_sec, &now);
+  size_t tm_buf_len = strftime(tm_buf.data(), tm_buf.size(), "%Y-%m-%d %H:%M:%S", &now);
+  if (tm_buf_len == 0) {
+    return "";
+  }
+
+  return stringtf("%s.%06ld", tm_buf.data(), tv.tv_usec);
 }
 
 std::string UriDecode( const std::string &encoded ) {

src/zm_utils.h

@@ -63,7 +63,7 @@ void hwcaps_detect();
 extern unsigned int sse_version;
 extern unsigned int neonversion;
 
-char *timeval_to_string( struct timeval tv );
+std::string TimevalToString(timeval tv);
 std::string UriDecode( const std::string &encoded );
 void touch( const char *pathname );