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v2.5.0 - Fix setenv/tzset Called on Every NMEA Timestamp Conversion (2026-02-24)

What Changed?

This release fixes gnss_manager.cpp to call setenv("TZ", "UTC0", 1) and tzset() only once at initialization instead of on every NMEA timestamp conversion. Previously, these calls were inside nmea_to_unix_timestamp_seconds(), which is invoked from the main loop whenever GNSS time is needed. Moving them to gnss_init() eliminates repeated heap allocation and global state mutation in the hot path.

What's New

Main Feature: Move setenv/tzset to gnss_init()

What it does:

Moves timezone initialization out of the per-call NMEA conversion helper into the one-time gnss_init() function:

Before:
  nmea_to_unix_timestamp_seconds()   // called every NMEA parse
    setenv("TZ", "UTC0", 1)          // heap alloc every call
    tzset()                           // global TZ re-init every call
    mktime()

After:
  gnss_init()                        // called once in setup()
    setenv("TZ", "UTC0", 1)          // heap alloc once
    tzset()                           // global TZ init once

  nmea_to_unix_timestamp_seconds()   // called every NMEA parse
    mktime()                          // TZ already set

Why it matters:

  • setenv() allocates heap memory on every call — on ESP32's constrained RAM, repeated calls cause heap fragmentation
  • tzset() re-initializes the global timezone state unnecessarily
  • TZ is always "UTC0" and never changes, so setting it once is correct and sufficient

Installation

Quick Start

# Get the release
git checkout 2.5.0

# Build
task v2:build

# Upload
task v2:upload

# Check it works
task monitor

What's Different from the Last Version?

🐛 Fixed

  • src/gnss_manager.cpp: setenv("TZ", "UTC0", 1) and tzset() moved from nmea_to_unix_timestamp_seconds() to gnss_init()

Is It Safe to Upgrade?

Backward Compatible: Yes

  • No change in behavior; UTC timezone was already set before every mktime() call
  • Only affects code path when ENABLE_GNSS=1

Tests Passed

  • ✅ Builds without errors

Release Details

  • Date: 2026-02-24
  • Version: v2.5.0
  • Files Changed: 1 (src/gnss_manager.cpp)

Next Steps

Continued code quality improvements (see REFACTORING_ROADMAP.md):

  • Remove double discard_input() call (P2, pending real-device verification)