ESP32 scanNetworks compile error: call of overloaded 'BSSID(int)' is ambiguous

Question

I am trying to run following code:

#include <WiFi.h>
void setup() {
 
 //int16_t scanNetworks(bool async = false, bool show_hidden = false, bool passive = false, uint32_t max_ms_per_chan = 300, uint8_t channel = 0, const char * ssid=nullptr, const uint8_t * bssid=nullptr);
 int n = WiFi.scanNetworks(true, false, false, 5, 7, "HTM");
 
 Serial.begin(115200);
 
 delay(10); // Minimum 10 milliseonds delay required to reliably receive message from Gateway.
 
 
 
 for (int i = 0; i < 4; i++) 
 {
 uint8_t values[4];
 values[i] = WiFi.BSSID(0)[i];
 
 }
} 
void loop() { } 

but I get an Arduino compile error (call of overloaded 'BSSID(int)' is ambiguous):

C:\Users\ebhynes\AppData\Local\Temp\arduino_modified_sketch_647803\sketch_apr04a.ino: In function 'void setup()':
sketch_apr04a:17:29: error: call of overloaded 'BSSID(int)' is ambiguous
 17 | values[i] = WiFi.BSSID(0)[i];
 | ~~~~~~~~~~^~~
In file included from C:\Users\ebhynes\AppData\Local\Arduino15\packages\esp32\hardware\esp323円.2.0\libraries\WiFi\src/WiFi.h:34,
 from C:\Users\ebhynes\AppData\Local\Temp\arduino_modified_sketch_647803\sketch_apr04a.ino:1:
C:\Users\ebhynes\AppData\Local\Arduino15\packages\esp32\hardware\esp323円.2.0\libraries\WiFi\src/WiFiSTA.h:171:12: note: candidate: 'uint8_t* WiFiSTAClass::BSSID(uint8_t*)'
 171 | uint8_t *BSSID(uint8_t *bssid = NULL);
 | ^~~~~
In file included from C:\Users\ebhynes\AppData\Local\Arduino15\packages\esp32\hardware\esp323円.2.0\libraries\WiFi\src/WiFi.h:36:
C:\Users\ebhynes\AppData\Local\Arduino15\packages\esp32\hardware\esp323円.2.0\libraries\WiFi\src/WiFiScan.h:52:12: note: candidate: 'uint8_t* WiFiScanClass::BSSID(uint8_t, uint8_t*)'
 52 | uint8_t *BSSID(uint8_t networkItem, uint8_t *bssid = NULL);
 | 

What is the solution?

• Juraj: values[i] = WiFi.BSSID( ((uint8_t) 0)[i]; to remove the ambiguity. not your error. they have a wrong API design
• the busybee: @Juraj Let's say that C++ has a design flaw, making 0 an integer and a pointer. :-D The issue comes up only because of the literal value 0. However, a good API would strive to work around.

Answer 1

Here is a slightly pruned version of the error message. If you take the time to read it carefully, it should hint you at the origin of the problem:

error: call of overloaded 'BSSID(int)' is ambiguous
candidate: uint8_t *BSSID(uint8_t *bssid = NULL);
candidate: uint8_t *BSSID(uint8_t networkItem, uint8_t *bssid = NULL);

This means that the method expects, as parameters:

• either an optional pointer (defaulting to NULL), which is the signature of the first candidate

• or a uint8_t number, optionally followed by a pointer (defaulting to NULL), which is the second candidate.

Since you called it with the single parameter 0, which is an int, the compiler does not know whether you meant for this parameter to be a pointer (first candidate) or a uint8_t (second candidate).

The solution is to be explicit about the type. Presumably:

values[i] = WiFi.BSSID(uint8_t(0))[i];