Build error: conversion from 'const ip_addr_t {aka const ip_addr}' to non-scalar type 'ip_addr_t {aka ip_addr}' requested

[GianCann]

What you are trying to do? Compile my esp32-arduino library with sdkconfig custom value (i need more of 3 BLE Max Connection)
Describe your system: PC with Ubuntu desktop
Describe what is failing.

I try to compiling esp32-arduino library following this guide:
https://github.com/espressif/arduino-esp32/blob/master/docs/lib_builder.md

I get this error:

/home/gianluca/esp32-arduino-lib-builder/components/arduino/libraries/WiFi/src/WiFiSTA.cpp: In member function 'IPAddress WiFiSTAClass::dnsIP(uint8_t)':
/home/gianluca/esp32-arduino-lib-builder/components/arduino/libraries/WiFi/src/WiFiSTA.cpp:491:37: error: conversion from 'const ip_addr_t {aka const ip_addr}' to non-scalar type 'ip_addr_t {aka ip_addr}' requested **
ip_addr_t dns_ip = dns_getserver(dns_no);
^
/home/gianluca/esp32-arduino-lib-builder/components/arduino/libraries/WiFi/src/ETH.cpp: In member function 'IPAddress ETHClass::dnsIP(uint8_t)':
/home/gianluca/esp32-arduino-lib-builder/components/arduino/libraries/WiFi/src/ETH.cpp:196:37: error: conversion from 'const ip_addr_t {aka const ip_addr}' to non-scalar type 'ip_addr_t {aka ip_addr}' requested**
ip_addr_t dns_ip = dns_getserver(dns_no);

Where is the problem?

[pivan76]

Ciao :-)

Try this:

In file:
/home/..../components/arduino/libraries/WiFi/src/WiFiSTA.cpp:491

IPAddress WiFiSTAClass::dnsIP(uint8_t dns_no)
{
if(WiFiGenericClass::getMode() == WIFI_MODE_NULL){
return IPAddress();
}
// ip_addr_t dns_ip = dns_getserver(dns_no);
// return IPAddress(dns_ip.u_addr.ip4.addr);
const ip_addr_t * dns_ip = dns_getserver(dns_no);
return IPAddress(dns_ip->u_addr.ip4.addr);
}

In file:
/home/..../components/arduino/libraries/WiFi/src/ETH.cpp:196

IPAddress ETHClass::dnsIP(uint8_t dns_no)
{
//ip_addr_t dns_ip = dns_getserver(dns_no);
//return IPAddress(dns_ip.u_addr.ip4.addr);
const ip_addr_t * dns_ip = dns_getserver(dns_no);
return IPAddress(dns_ip->u_addr.ip4.addr);
}

This fix is from version 4.0 of the arduino-esp32 found here:
https://github.com/espressif/arduino-esp32/blob/idf-release/v4.0/libraries/WiFi/src/WiFiSTA.cpp

If you get the error "Please configure IDF framework to include mbedTLS -> Enable pre-shared-key ciphersuites and activate at least the path in menuconfig is:

component config > mbedTLS > TLS key exchange method > enable pre-shared keys & enable psk

Ivan

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[copercini]

@me-no-dev I think this fix should be included in master, because it generates a build error when using arduino as component of IDF 3.3.2 without it
EDIT: this is already implemented in 3.3 branch 3da04ce