src: Add code in case struct tm.tm_gmtoff is not available

configure.ac

@@ -468,6 +468,14 @@ AC_CHECK_TYPES([ptrdiff_t])
 AC_C_BIGENDIAN
 AC_SYS_LARGEFILE
 
+AC_CHECK_MEMBER([struct tm.tm_gmtoff], [have_struct_tm_tm_gmtoff=yes],
+                [have_struct_tm_tm_gmtoff=no], [[#include <time.h>]])
+
+if test "x$have_struct_tm_tm_gmtoff" = "xyes"; then
+  AC_DEFINE([HAVE_STRUCT_TM_TM_GMTOFF], [1],
+            [Define to 1 if you have `struct tm.tm_gmtoff` member.])
+fi
+
 # Checks for library functions.
 if test "x$cross_compiling" != "xyes"; then
   AC_FUNC_MALLOC

src/util.cc

@@ -231,6 +231,7 @@ std::string common_log_date(time_t t)
     return "";
   }
 
+#ifdef HAVE_STRUCT_TM_TM_GMTOFF
   // Format data like this:
   // 03/Jul/2014:00:19:38 +0900
   std::string res;
@@ -264,6 +265,13 @@ std::string common_log_date(time_t t)
   p = cpydig(p, (gmtoff % 3600) / 60, 2);
 
   return res;
+#else // !HAVE_STRUCT_TM_TM_GMTOFF
+  char buf[32];
+
+  strftime(buf, sizeof(buf), "%d/%b/%Y:%T %z", &tms);
+
+  return buf;
+#endif // !HAVE_STRUCT_TM_TM_GMTOFF
 }
 
 std::string iso8601_date(int64_t ms)
@@ -275,6 +283,7 @@ std::string iso8601_date(int64_t ms)
     return "";
   }
 
+#ifdef HAVE_STRUCT_TM_TM_GMTOFF
   // Format data like this:
   // 2014-11-15T12:58:24.741Z
   // 2014-11-15T12:58:24.741+09:00
@@ -315,6 +324,29 @@ std::string iso8601_date(int64_t ms)
   res.resize(p - std::begin(res));
 
   return res;
+#else // !HAVE_STRUCT_TM_TM_GMTOFF
+  char buf[128];
+
+  auto nwrite = strftime(buf, sizeof(buf), "%Y-%m-%dT%H:%M:%S", &tms);
+  nwrite += snprintf(&buf[nwrite], sizeof(buf) - nwrite, ".%03d",
+                     static_cast<int>(ms % 1000));
+  auto nzone = strftime(&buf[nwrite], sizeof(buf) - nwrite, "%z", &tms);
+
+  // %z of strftime writes +hhmm or -hhmm not Z, +hh:mm or -hh:mm.  Do
+  // %nothing if nzone is not 5.  we don't know how to cope with this.
+  if(nzone == 5) {
+    if(memcmp(&buf[nwrite], "+0000", 5) == 0) {
+      // 0000 should be Z
+      memcpy(&buf[nwrite], "Z", 2);
+    } else {
+      // Move mm part to right by 1 including terminal \0
+      memmove(&buf[nwrite + 4], &buf[nwrite + 3], 3);
+      // Insert ':' between hh and mm
+      buf[nwrite + 3] = ':';
+    }
+  }
+  return buf;
+#endif // !HAVE_STRUCT_TM_TM_GMTOFF
 }
 
 time_t parse_http_date(const std::string& s)