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

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/>