If I want to use library functions from stdio.h and stdlib.h am i amble to declare those header files in an arduino IDE code file? Or are those headers and associated library functions already built into arduino coding when I use the arduino IDE to tweak some arduino code file?

I'm trying to set up an environment for an ESP8266 Wemos with VSCode and the Arduino plugin. Apparently, verify + deploy works, but Intellisense throws an error for the "ESP8266WiFi.h" header, namely that

 cannot open source file "stdlib.h" (dependency of "C:\Users\[me]\AppData\Local\Arduino15\packages\esp8266\hardware\esp8266\3.1.1\cores\esp8266\Arduino.h") 

I found the ESP board manager's stdlib.h under the folder

C:\Users\[still me]\AppData\Local\Arduino15\packages\esp8266\tools\xtensa-lx106-elf-gcc\3.1.0-gcc10.3-e5f9fec\xtensa-lx106-elf\include

But if I add it to the c_cpp_properties.json the ^(probably) plugin instantly removes it at the next intellisense analyze session, thus still causing an error message.

The whole cpp file:

{
    "version": 4,
    "configurations": [
        {
            "name": "Arduino",
            "compilerPath": "@C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\tools\\warnings\\none-g++",
            "compilerArgs": [
                "-U__STRICT_ANSI__",
                "-free",
                "-fipa-pta",
                "-Werror=return-type",
                "-mlongcalls",
                "-mtext-section-literals",
                "-fno-rtti",
                "-falign-functions=4",
                "-std=gnu++17"
            ],
            "intelliSenseMode": "gcc-x64",
            "includePath": [
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\tools\\sdk\\include",
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\tools\\sdk\\lwip2\\include",
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\cores\\esp8266",
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\variants\\d1_mini",
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\libraries\\ESP8266WiFi\\src",
                "C:\\Users\\[me]\\Documents\\Arduino\\libraries\\PubSubClient-2.8.0\\src"
            ],
            "forcedInclude": [
                "C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\cores\\esp8266\\Arduino.h"
            ],
            "cStandard": "c11",
            "cppStandard": "c++17",
            "defines": [
                "__ets__",
                "ICACHE_FLASH",
                "_GNU_SOURCE",
                "ESP8266",
                "MMU_IRAM_SIZE=0x8000",
                "MMU_ICACHE_SIZE=0x8000",
                "NONOSDK22x_190703=1",
                "F_CPU=80000000L",
                "LWIP_OPEN_SRC",
                "TCP_MSS=536",
                "LWIP_FEATURES=1",
                "LWIP_IPV6=0",
                "ARDUINO=10813",
                "ARDUINO_ESP8266_WEMOS_D1MINI",
                "ARDUINO_ARCH_ESP8266",
                "ARDUINO_BOARD=\"ESP8266_WEMOS_D1MINI\"",
                "ARDUINO_BOARD_ID=\"d1_mini_clone\"",
                "FLASHMODE_DOUT",
                "USBCON"
            ]
        }
    ]
}

Fun part 2:

The @C:\\Users\\[me]\\AppData\\Local\\Arduino15\\packages\\esp8266\\hardware\\esp8266\\3.1.1\\tools\\warnings\\none-g++ also seem to be corrupted because thanks to the @, the intellisense interprets it as [projectpath]\[path from json] instead of an absolute path. Altho building works, the VSCode constantly highlights the json file for errors. Whenever I change this, the ^(probably) plugin instantly changes it back to this nonsense.