Experiment: C++17 support (#9874)

* Add C++17 support

* Add C++17 runtime probes and update build configurations for STM32 and Portduino

* Remove unflags

* Update C++ standard flags across the platforms

* Convert a couple of instances to structured bindings

* NRF52 platform.txt to add C++17 support

* Still need the unflags apparently

* Remove C++17 runtime probe tests from test_main.cpp

* Reconfigured doesnt need a nodiscard

* Remove nodiscard attribute from init() method in RadioInterface

* Remove mbedtls/error.h from build flags

Removed include directive for mbedtls/error.h from build flags.

* Fix IRAM overflow

* Fix IRAM overflow

* Add build flag to exclude MQTT from rak11200

* Update C++ standard from gnu17 to gnu++17

platformio.ini

@@ -97,7 +97,11 @@ lib_deps =
 	${env.lib_deps}
 	# renovate: datasource=custom.pio depName=NonBlockingRTTTL packageName=end2endzone/library/NonBlockingRTTTL
 	end2endzone/NonBlockingRTTTL@1.4.0
+build_unflags =
+	-std=c++11
+	-std=gnu++11
 build_flags = ${env.build_flags} -Os
+	-std=gnu++17
 build_src_filter = ${env.build_src_filter} -<platform/portduino/> -<graphics/niche/>
 
 ; Common libs for communicating over TCP/IP networks such as MQTT

src/mesh/NextHopRouter.cpp

@@ -23,7 +23,7 @@ ErrorCode NextHopRouter::send(meshtastic_MeshPacket *p)
     p->relay_node = nodeDB->getLastByteOfNodeNum(getNodeNum()); // First set the relayer to us
     wasSeenRecently(p);                                         // FIXME, move this to a sniffSent method
 
-    p->next_hop = getNextHop(p->to, p->relay_node); // set the next hop
+    p->next_hop = getNextHop(p->to, p->relay_node).value_or(NO_NEXT_HOP_PREFERENCE); // set the next hop
     LOG_DEBUG("Setting next hop for packet with dest %x to %x", p->to, p->next_hop);
 
     // If it's from us, ReliableRouter already handles retransmissions if want_ack is set. If a next hop is set and hop limit is
@@ -170,10 +170,10 @@ bool NextHopRouter::perhapsRebroadcast(const meshtastic_MeshPacket *p)
  * Get the next hop for a destination, given the relay node
  * @return the node number of the next hop, 0 if no preference (fallback to FloodingRouter)
  */
-uint8_t NextHopRouter::getNextHop(NodeNum to, uint8_t relay_node)
+std::optional<uint8_t> NextHopRouter::getNextHop(NodeNum to, uint8_t relay_node)
 {
     if (isBroadcast(to))
-        return NO_NEXT_HOP_PREFERENCE;
+        return std::nullopt;
 
     meshtastic_NodeInfoLite *node = nodeDB->getMeshNode(to);
     if (node && node->next_hop) {
@@ -184,7 +184,7 @@ uint8_t NextHopRouter::getNextHop(NodeNum to, uint8_t relay_node)
         } else
             LOG_WARN("Next hop for 0x%x is 0x%x, same as relayer; set no pref", to, node->next_hop);
     }
-    return NO_NEXT_HOP_PREFERENCE;
+    return std::nullopt;
 }
 
 PendingPacket *NextHopRouter::findPendingPacket(GlobalPacketId key)

src/mesh/NextHopRouter.h

@@ -1,6 +1,7 @@
 #pragma once
 
 #include "FloodingRouter.h"
+#include <optional>
 #include <unordered_map>
 
 /**
@@ -146,7 +147,7 @@ class NextHopRouter : public FloodingRouter
      * Get the next hop for a destination, given the relay node
      * @return the node number of the next hop, 0 if no preference (fallback to FloodingRouter)
      */
-    uint8_t getNextHop(NodeNum to, uint8_t relay_node);
+    std::optional<uint8_t> getNextHop(NodeNum to, uint8_t relay_node);
 
     /** Check if we should be rebroadcasting this packet if so, do so.
      *  @return true if we did rebroadcast */

src/mesh/RadioInterface.h

@@ -156,7 +156,7 @@ class RadioInterface
     virtual ErrorCode send(meshtastic_MeshPacket *p) = 0;
 
     /** Return TX queue status */
-    virtual meshtastic_QueueStatus getQueueStatus()
+    [[nodiscard]] virtual meshtastic_QueueStatus getQueueStatus()
     {
         meshtastic_QueueStatus qs;
         qs.res = qs.mesh_packet_id = qs.free = qs.maxlen = 0;
@@ -182,22 +182,22 @@ class RadioInterface
     virtual bool reconfigure();
 
     /** The delay to use for retransmitting dropped packets */
-    uint32_t getRetransmissionMsec(const meshtastic_MeshPacket *p);
+    [[nodiscard]] uint32_t getRetransmissionMsec(const meshtastic_MeshPacket *p);
 
     /** The delay to use when we want to send something */
-    uint32_t getTxDelayMsec();
+    [[nodiscard]] uint32_t getTxDelayMsec();
 
     /** The CW to use when calculating SNR_based delays */
-    uint8_t getCWsize(float snr);
+    [[nodiscard]] uint8_t getCWsize(float snr);
 
     /** The worst-case SNR_based packet delay */
-    uint32_t getTxDelayMsecWeightedWorst(float snr);
+    [[nodiscard]] uint32_t getTxDelayMsecWeightedWorst(float snr);
 
     /** Returns true if we should rebroadcast early like a ROUTER */
-    bool shouldRebroadcastEarlyLikeRouter(meshtastic_MeshPacket *p);
+    [[nodiscard]] bool shouldRebroadcastEarlyLikeRouter(meshtastic_MeshPacket *p);
 
     /** The delay to use when we want to flood a message. Use a weighted scale based on SNR */
-    uint32_t getTxDelayMsecWeighted(meshtastic_MeshPacket *p);
+    [[nodiscard]] uint32_t getTxDelayMsecWeighted(meshtastic_MeshPacket *p);
 
     /** If the packet is not already in the late rebroadcast window, move it there */
     virtual void clampToLateRebroadcastWindow(NodeNum from, PacketId id) { return; }
@@ -215,18 +215,18 @@ class RadioInterface
      *
      * @return num msecs for the packet
      */
-    uint32_t getPacketTime(const meshtastic_MeshPacket *p, bool received = false);
-    virtual uint32_t getPacketTime(uint32_t totalPacketLen, bool received = false) = 0;
+    [[nodiscard]] uint32_t getPacketTime(const meshtastic_MeshPacket *p, bool received = false);
+    [[nodiscard]] virtual uint32_t getPacketTime(uint32_t totalPacketLen, bool received = false) = 0;
 
     /**
      * Get the channel we saved.
      */
-    uint32_t getChannelNum();
+    [[nodiscard]] uint32_t getChannelNum();
 
     /**
      * Get the frequency we saved.
      */
-    virtual float getFreq();
+    [[nodiscard]] virtual float getFreq();
 
     /// Some boards (1st gen Pinetab Lora module) have broken IRQ wires, so we need to poll via i2c registers
     virtual bool isIRQPending() { return false; }
@@ -246,7 +246,7 @@ class RadioInterface
      *
      * Used as the first step of
      */
-    size_t beginSending(meshtastic_MeshPacket *p);
+    [[nodiscard]] size_t beginSending(meshtastic_MeshPacket *p);
 
     /**
      * Some regulatory regions limit xmit power.

src/mesh/Router.h

@@ -58,14 +58,14 @@ class Router : protected concurrency::OSThread, protected PacketHistory
     /** Allocate and return a meshpacket which defaults as send to broadcast from the current node.
      * The returned packet is guaranteed to have a unique packet ID already assigned
      */
-    meshtastic_MeshPacket *allocForSending();
+    [[nodiscard]] meshtastic_MeshPacket *allocForSending();
 
     /** Return Underlying interface's TX queue status */
-    meshtastic_QueueStatus getQueueStatus();
+    [[nodiscard]] meshtastic_QueueStatus getQueueStatus();
 
     /**
      * @return our local nodenum */
-    NodeNum getNodeNum();
+    [[nodiscard]] NodeNum getNodeNum();
 
     /** Wake up the router thread ASAP, because we just queued a message for it.
      * FIXME, this is kinda a hack because we don't have a nice way yet to say 'wake us because we are 'blocked on this queue'

src/mesh/TransmitHistory.cpp

@@ -141,12 +141,12 @@ bool TransmitHistory::saveToDisk()
         file.write((uint8_t *)&header, sizeof(header));
 
         uint8_t written = 0;
-        for (auto &pair : history) {
+        for (const auto &[key, epochSeconds] : history) {
             if (written >= MAX_ENTRIES)
                 break;
             Entry entry{};
-            entry.key = pair.first;
-            entry.epochSeconds = pair.second;
+            entry.key = key;
+            entry.epochSeconds = epochSeconds;
             file.write((uint8_t *)&entry, sizeof(entry));
             written++;
         }

src/mqtt/MQTT.cpp

@@ -300,7 +300,9 @@ struct PubSubConfig {
         if (config.tls_enabled) {
             serverPort = 8883;
         }
-        std::tie(serverAddr, serverPort) = parseHostAndPort(serverAddr.c_str(), serverPort);
+        auto [parsedServerAddr, parsedServerPort] = parseHostAndPort(serverAddr.c_str(), serverPort);
+        serverAddr = std::move(parsedServerAddr);
+        serverPort = parsedServerPort;
     }
 
     // Defaults
@@ -441,7 +443,8 @@ MQTT::MQTT() : concurrency::OSThread("mqtt"), mqttQueue(MAX_MQTT_QUEUE)
                 moduleConfig.mqtt.map_report_settings.publish_interval_secs, default_map_publish_interval_secs);
         }
 
-        String host = parseHostAndPort(moduleConfig.mqtt.address).first;
+        auto [host, parsedPort] = parseHostAndPort(moduleConfig.mqtt.address);
+        (void)parsedPort;
         isConfiguredForDefaultServer = isDefaultServer(host);
         IPAddress ip;
         isMqttServerAddressPrivate = ip.fromString(host.c_str()) && isPrivateIpAddress(ip);

variants/esp32/esp32-common.ini

@@ -27,7 +27,12 @@ board_build.filesystem = littlefs
 # Remove -DMYNEWT_VAL_BLE_HS_LOG_LVL=LOG_LEVEL_CRITICAL for low level BLE logging.
 # See library directory for BLE logging possible values: .pio/libdeps/tbeam/NimBLE-Arduino/src/log_common/log_common.h
 # This overrides the BLE logging default of LOG_LEVEL_INFO (1) from: .pio/libdeps/tbeam/NimBLE-Arduino/src/esp_nimble_cfg.h
-build_unflags = -fno-lto
+build_unflags =
+  -fno-lto
+  # Keep explicit std unflags on ESP32; base-level unflags are not sufficient
+  # to prevent framework-injected C++11 fallback on this platform.
+  -std=c++11
+  -std=gnu++11
 build_flags =
   ${arduino_base.build_flags}
   -flto
@@ -35,7 +40,7 @@ build_flags =
   -Wextra
   -Isrc/platform/esp32
   -include mbedtls/error.h
-  -std=c++11
+  -std=gnu++17
   -DLOG_LOCAL_LEVEL=ESP_LOG_DEBUG
   -DCORE_DEBUG_LEVEL=ARDUHAL_LOG_LEVEL_DEBUG
   -DMYNEWT_VAL_BLE_HS_LOG_LVL=LOG_LEVEL_CRITICAL

variants/esp32/rak11200/platformio.ini

@@ -16,4 +16,8 @@ build_flags =
   ${esp32_base.build_flags}
   -D RAK_11200
   -I variants/esp32/rak11200
+  -DMESHTASTIC_EXCLUDE_WEBSERVER=1
+  -DMESHTASTIC_EXCLUDE_PAXCOUNTER=1
+  -DMESHTASTIC_EXCLUDE_RANGETEST=1
+  -DMESHTASTIC_EXCLUDE_MQTT=1
 upload_speed = 115200

variants/esp32c6/esp32c6.ini

@@ -8,7 +8,6 @@ build_flags =
   -Wall
   -Wextra
   -Isrc/platform/esp32
-  -std=c++11
   -DESP_OPENSSL_SUPPRESS_LEGACY_WARNING
   -DSERIAL_BUFFER_SIZE=4096
   -DLIBPAX_ARDUINO

variants/native/portduino.ini

@@ -55,8 +55,7 @@ build_flags =
   -li2c
   -luv
   -std=gnu17
-  -std=c++17
-
+  -std=gnu++17
 lib_ignore =
   Adafruit NeoPixel
   Adafruit ST7735 and ST7789 Library

variants/nrf52840/nrf52.ini

@@ -5,9 +5,9 @@ platform =
   platformio/nordicnrf52@10.11.0
 extends = arduino_base
 platform_packages =
-  ; our custom Git version until they merge our PR
+  ; our custom Git version with C++17 support in platform.txt
   # TODO renovate
-  platformio/framework-arduinoadafruitnrf52 @ https://github.com/meshtastic/Adafruit_nRF52_Arduino#74096746e5f167a2ff22e483d8e79bb1aef00591
+  platformio/framework-arduinoadafruitnrf52 @ https://github.com/meshtastic/Adafruit_nRF52_Arduino#cpp17-platform
   ; Don't renovate toolchain-gccarmnoneeabi
   platformio/toolchain-gccarmnoneeabi@~1.90301.0
 
@@ -35,6 +35,8 @@ build_unflags =
   -g
   -g1
   -g0
+  -std=c++11
+  -std=gnu++11
 
 build_src_filter = 
   ${arduino_base.build_src_filter} -<platform/esp32/> -<platform/stm32wl> -<nimble/> -<mesh/wifi/> -<mesh/api/> -<mesh/http/> -<modules/esp32> -<platform/rp2xx0> -<mesh/eth/> -<mesh/raspihttp> -<serialization/>