I have got an telnet server with esp8266 + SoftwareSerial+ UNO, and here I want to on led with command ON . will be 1 or 2. It is for recive 1 or 2 numbered pins. And I extract pin from request with indexOf and substring functions and write:


I write if pin is not 0 or 1 and it is in range 2-9 for type 1 and if pin is in range 10-13. But at compile time it gives me error compiling for uno. And it gives me this error whn I use pinMode. When I write it to setup it don't give me error. Why? What happenes?

Full code:

#include "WiFiEsp.h"

// Emulate Serial1 on pins 6/7 if not present
#include "SoftwareSerial.h"
SoftwareSerial Serial1(6, 7); // RX, TX
 String res = "";
char ssid[] = "ssid";            // your network SSID (name)
char pass[] = "passs";         // your network password
int status = WL_IDLE_STATUS;     // the Wifi radio's status
int reqCount = 0;                // number of requests received

WiFiEspServer server(23);

 WiFiEspClient client;

void setup() {

  // initialize serial for ESP module
  // initialize ESP module

  // check for the presence of the shield
  if (WiFi.status() == WL_NO_SHIELD) {
    Serial.println("WiFi shield not present");
    // don't continue
    while (true);

  while ( status != WL_CONNECTED) {
    Serial.print("Attempting to connect to WPA SSID: ");
    // Connect to WPA/WPA2 network
    status = WiFi.begin(ssid, pass);

  Serial.println("You're connected to the network");


  // start the web server on port 80

void loop(){
    client = server.available();
      client.println("Welcome to telnet server!,");


  res = "";

char c = client.read();

res += c;


int i = res.indexOf("ON")+3;
int j = i+1;
String hh = res.substring(i,j);
int type = hh.toInt();
if(type == 1) 
  int ii = res.indexOf("ON")+5;
int jj = ii+1;
String hhh = res.substring(ii,jj);
int ihhh = hhh.toInt();
if(ihhh != 0 && ihhh != 1 && (2 <=ihhh)&& ( ihhh <= 9 ))
  client.print("Pin is TX/RX, or not 2<= pin <=9\r\n");
}else if(type == 2){
    int iii = res.indexOf("ON")+5;
int jjj = iii+2;
String hhhh = res.substring(iii,jjj);
int ihhhh = hhhh.toInt();
if(ihhhh != 0 && ihhhh != 1 && !((2<=ihhhh)&&(ihhhh <= 9)) && (10 <= ihhhh)&&(ihhhh <= 13 ))
  client.print("Pin is TX/RX, or not 2<= pin <=9\r\n");


    Serial.println("Client disconnected from Telnet Server");



Error is:

Arduino: 1.8.9 (Windows Store (Windows 10), Board: "Arduino/Genuino Uno"

C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.21.0_x86__mdqgnx93n4wtt\hardware\arduino\avr\cores\arduino\HardwareSerial.cpp: In member function 'availableForWrite':

C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.21.0_x86__mdqgnx93n4wtt\hardware\arduino\avr\cores\arduino\HardwareSerial.cpp:203:1: internal compiler error: Segmentation fault



Please submit a full bug report,

with preprocessed source if appropriate.

See http://gcc.gnu.org/bugs.html for instructions.

lto-wrapper.exe: fatal error: C:\Program Files\WindowsApps\ArduinoLLC.ArduinoIDE_1.8.21.0_x86__mdqgnx93n4wtt\hardware\tools\avr/bin/avr-gcc returned 1 exit status

compilation terminated.

c:/program files/windowsapps/arduinollc.arduinoide_1.8.21.0_x86__mdqgnx93n4wtt/hardware/tools/avr/bin/../lib/gcc/avr/5.4.0/../../../../avr/bin/ld.exe: error: lto-wrapper failed

collect2.exe: error: ld returned 1 exit status

exit status 1 Error compiling for board Arduino/Genuino Uno.

Arduino IDE version is: 1.8.9(Windows Store

  • 1
    You forgot to include the error message. Please format your code correctly (use autoformat in the IDE, delete unnecessary empty lines, and fix the indentation).
    – tttapa
    Commented Aug 13, 2019 at 12:14
  • What is the exact text of the error (all the error, not just the last line). Also, what version of the IDE are you using, and what version of the AVR boards package, and how did you install the IDE?
    – Majenko
    Commented Aug 13, 2019 at 12:14
  • I thought it might be the "windows store" version. Known to be broken. Delete it. Download the IDE properly from the Arduino website.
    – Majenko
    Commented Aug 13, 2019 at 13:08
  • @Majenko I didn't know that, what's the difference compared to the "normal" version?
    – tttapa
    Commented Aug 13, 2019 at 13:28
  • It bundles a broken version of the compiler.
    – Majenko
    Commented Aug 13, 2019 at 13:29

1 Answer 1


This is a bug in the compiler (linker) used by the Arduino AVR Core. It's not because of a bug in your code, and there's not much you can do about it except using a different version of the AVR Core.

See this forum post:

Here's the traditional workaround:

  1. Tools > Board > Boards Manager
  2. Wait for downloads to finish.
  3. When you move the mouse pointer over "Arduino AVR Boards", you will see a "Select version" dropdown menu appear. Select "1.6.21".
  4. Click "Install".
  5. Wait for installation to finish.
  6. Click "Close".

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