PIO extra script to silence viotile warnings, cased by external libraries, after the upgrade to C++20

Author: MacDada

config/nodemcu.ini

@@ -82,3 +82,7 @@ build_src_filter = "+<arduino.cpp>"
 ; https://docs.platformio.org/en/latest/projectconf/section_env_test.html#test-filter
 ; todo: is it even possible to configure tests on NodeMcu?
 test_filter = embedded/*
+
+; https://docs.platformio.org/en/latest/projectconf/sections/env/options/advanced/extra_scripts.html
+; https://docs.platformio.org/en/latest/scripting/actions.html
+extra_scripts = post:scripts/pio_post_extra_script.py

scripts/pio_post_extra_script.py

@@ -0,0 +1,42 @@
+# Activate the script with `extra_scripts = pre:scripts/pio_post_extra_script.py` in `platformio.ini` config.
+#
+# https://docs.platformio.org/en/latest/projectconf/sections/env/options/advanced/extra_scripts.html
+# https://docs.platformio.org/en/latest/scripting/actions.html
+
+Import("env")
+
+# Silencing `volatile` warnings
+#
+# There is a lot "invalid" usages of `volatile` in the external libraries (dependencies):
+#
+# > .platformio/packages/framework-arduinoespressif8266/cores/esp8266/core_esp8266_i2s.cpp:179:23:
+# > warning: '++' expression of 'volatile'-qualified type is deprecated [-Wvolatile]
+#
+# The problem appears with the upgrade to C++20,
+# but they apparently de-deprecated it in C++23,
+# so there is little to no will to fix the usages:
+# https://github.com/esp8266/Arduino/issues/8916
+#
+# Therefore, I'm silencing `volatile`, so that the build keeps being clean,
+# and I don't miss any issues within _my_ code, hidden between the dependencies shitstorm.
+# Luckily, I don't use `volatile` myself, so _my_ code should not be at risk.
+#
+# todo: remove the the silencing, when GCC is upgraded, and I can use C++23 standard,
+#       or if they fix the issues in the libs (not gonna happen ;p)
+#
+# I cannot set the flag with `build_flags`, because then it applies to both C++ and C,
+# while it is not valid for C -> and the warning appears:
+#
+# > cc1: warning: command-line option '-Wno-volatile' is valid for C++/ObjC++ but not for C
+#
+# Therefore, "hacking" with the `extra_scripts`:
+#  * https://github.com/platformio/platformio-core/issues/1728
+#  * https://github.com/platformio/platformio-core/issues/2144
+#    * todo: get rid of `extra_scripts` when a "native to PIO" `build_flags` option can be properly set
+#  * https://community.platformio.org/t/separate-settings-for-c-and-c-versions/21647
+#  * https://community.platformio.org/t/silence-warnings-for-dependencies-external-libraries/33387
+#
+# Using `env` as it applies to everything, including the external libraries,
+# while `projectenv` would apply only to _my_ code,
+# https://github.com/platformio/platformio-core/issues/1728#issuecomment-403297776
+env.Append(CXXFLAGS=["-Wno-volatile"])