Fix issue #3483

CMakeLists.txt

@@ -97,6 +97,8 @@ option(SPDLOG_USE_STD_FORMAT "Use std::format instead of fmt library." OFF)
 option(SPDLOG_FMT_EXTERNAL "Use external fmt library instead of bundled" OFF)
 option(SPDLOG_FMT_EXTERNAL_HO "Use external fmt header-only library instead of bundled" OFF)
 option(SPDLOG_NO_EXCEPTIONS "Compile with -fno-exceptions. Call abort() on any spdlog exceptions" OFF)
+option(SPDLOG_NO_TZ_OFFSET "Omit %z timezone offset (use on platforms without tm_gmtoff)" OFF)
+
 
 if(SPDLOG_FMT_EXTERNAL AND SPDLOG_FMT_EXTERNAL_HO)
     message(FATAL_ERROR "SPDLOG_FMT_EXTERNAL and SPDLOG_FMT_EXTERNAL_HO are mutually exclusive")
@@ -286,7 +288,9 @@ foreach(
     SPDLOG_NO_TLS
     SPDLOG_NO_ATOMIC_LEVELS
     SPDLOG_DISABLE_DEFAULT_LOGGER
-    SPDLOG_USE_STD_FORMAT)
+    SPDLOG_USE_STD_FORMAT
+    SPDLOG_NO_TZ_OFFSET
+)
     if(${SPDLOG_OPTION})
         target_compile_definitions(spdlog PUBLIC ${SPDLOG_OPTION})
         target_compile_definitions(spdlog_header_only INTERFACE ${SPDLOG_OPTION})

include/spdlog/details/os-inl.h

@@ -244,6 +244,7 @@ SPDLOG_INLINE size_t filesize(FILE *f) {
 #endif
 
 // Return utc offset in minutes or throw spdlog_ex on failure
+#if !defined(SPDLOG_NO_TZ_OFFSET)
 SPDLOG_INLINE int utc_minutes_offset(const std::tm &tm) {
 #ifdef _WIN32
     #if _WIN32_WINNT < _WIN32_WINNT_WS08
@@ -263,46 +264,11 @@ SPDLOG_INLINE int utc_minutes_offset(const std::tm &tm) {
     }
     return offset;
 #else
-
-    #if defined(sun) || defined(__sun) || defined(_AIX) ||                        \
-        (defined(__NEWLIB__) && !defined(__TM_GMTOFF)) ||                         \
-        (!defined(__APPLE__) && !defined(_BSD_SOURCE) && !defined(_GNU_SOURCE) && \
-         (!defined(_POSIX_VERSION) || (_POSIX_VERSION < 202405L)))
-    // 'tm_gmtoff' field is BSD extension and it's missing on SunOS/Solaris
-    struct helper {
-        static long int calculate_gmt_offset(const std::tm &localtm = details::os::localtime(),
-                                             const std::tm &gmtm = details::os::gmtime()) {
-            int local_year = localtm.tm_year + (1900 - 1);
-            int gmt_year = gmtm.tm_year + (1900 - 1);
-
-            long int days = (
-                // difference in day of year
-                localtm.tm_yday -
-                gmtm.tm_yday
-
-                // + intervening leap days
-                + ((local_year >> 2) - (gmt_year >> 2)) - (local_year / 100 - gmt_year / 100) +
-                ((local_year / 100 >> 2) - (gmt_year / 100 >> 2))
-
-                // + difference in years * 365 */
-                + static_cast<long int>(local_year - gmt_year) * 365);
-
-            long int hours = (24 * days) + (localtm.tm_hour - gmtm.tm_hour);
-            long int mins = (60 * hours) + (localtm.tm_min - gmtm.tm_min);
-            long int secs = (60 * mins) + (localtm.tm_sec - gmtm.tm_sec);
-
-            return secs;
-        }
-    };
-
-    auto offset_seconds = helper::calculate_gmt_offset(tm);
-    #else
     auto offset_seconds = tm.tm_gmtoff;
-    #endif
-
     return static_cast<int>(offset_seconds / 60);
 #endif
 }
+#endif // SPDLOG_NO_TZ_OFFSET
 
 // Return current thread id as size_t
 // It exists because the std::this_thread::get_id() is much slower(especially

include/spdlog/pattern_formatter-inl.h

@@ -510,6 +510,7 @@ public:
 };
 
 // ISO 8601 offset from UTC in timezone (+-HH:MM)
+// If SPDLOG_NO_TZ_OFFSET is defined, print "+??.??" instead.
 template <typename ScopedPadder>
 class z_formatter final : public flag_formatter {
 public:
@@ -524,6 +525,10 @@ public:
         const size_t field_size = 6;
         ScopedPadder p(field_size, padinfo_, dest);
 
+        #ifdef SPDLOG_NO_TZ_OFFSET
+        const char *str = "+??:??";
+        dest.append(str, str + 6);
+        #else
         auto total_minutes = get_cached_offset(msg, tm_time);
         bool is_negative = total_minutes < 0;
         if (is_negative) {
@@ -536,6 +541,7 @@ public:
         fmt_helper::pad2(total_minutes / 60, dest);  // hours
         dest.push_back(':');
         fmt_helper::pad2(total_minutes % 60, dest);  // minutes
+        #endif // SPDLOG_NO_TZ_OFFSET
     }
 
 private:
@@ -1154,12 +1160,10 @@ SPDLOG_INLINE void pattern_formatter::handle_flag_(char flag, details::padding_i
             formatters_.push_back(details::make_unique<details::T_formatter<Padder>>(padding));
             need_localtime_ = true;
             break;
-
         case ('z'):  // timezone
-            formatters_.push_back(details::make_unique<details::z_formatter<Padder>>(padding));
-            need_localtime_ = true;
+                formatters_.push_back(details::make_unique<details::z_formatter<Padder>>(padding));
+                need_localtime_ = true;
             break;
-
         case ('P'):  // pid
             formatters_.push_back(details::make_unique<details::pid_formatter<Padder>>(padding));
             break;

tests/test_pattern_formatter.cpp

@@ -82,8 +82,12 @@ TEST_CASE("GMT offset ", "[pattern_formatter]") {
     const auto now = std::chrono::system_clock::now();
     const auto yesterday = now - 24h;
 
-    REQUIRE(log_to_str_with_time(yesterday, "Some message", "%z", spdlog::pattern_time_type::utc,
-                                 "\n") == "+00:00\n");
+#ifndef SPDLOG_NO_TZ_OFFSET
+    const std::string expected_result = "+00:00\n";
+#else
+    const std::string expected_result = "+??:??\n";
+#endif
+    REQUIRE(log_to_str_with_time(yesterday, "Some message", "%z", spdlog::pattern_time_type::utc, "\n") == expected_result);
 }
 
 TEST_CASE("color range test1", "[pattern_formatter]") {