strcasestr ESP8266 error

I have been searching for answers to this everywhere but to no avail. I am trying to use strcasestr in the Arduino IDE on ESP8266 boards. During compilation, I get this error "undefined reference to 'strcasestr". The error does not occur when using strstr, only occurs using strcasestr. The error also does not occur when compiling using Arduino boards.

I ran across and tried this but to no avail c - How do I use strcasestr()? - Stack Overflow. I also checked the esp8266 string.h file, and the strcasestr entry seems to exist.

Could someone point me in the right direction / tell me which file should I look into or edit, to find a potential solution to solve the error.

Byork:
Could someone point me in the right direction / tell me which file should I look into or edit, to find a potential solution to solve the error.

I'm not familiar with the hardware, but you could try this:

#ifdef __cplusplus
extern "C"{
#endif

char* strcasestr(const char* target, const char* search);

#ifdef __cplusplus
}
#endif

char bigString[] = "this is my target string";
char littleString[] = "MY";

void setup() 
{
  Serial.begin(9600);
  char* ptr = strcasestr(bigString, littleString);
  Serial.println(ptr);
}

void loop() {}

Appreciate the reply BulldogLowell. I have copied and paste your code exactly into a blank sketch and tried compiling. I still get the same exact error.

sketch\sketch_jul30a.ino.cpp.o:(.text.setup+0x8): undefined reference to `strcasestr'

sketch\sketch_jul30a.ino.cpp.o: In function `setup':

C:\Users\Byork\AppData\Local\Temp\arduino_modified_sketch_355779/sketch_jul30a.ino:19: undefined reference to `strcasestr'

collect2.exe: error: ld returned 1 exit status

exit status 1
Error compiling for board Generic ESP8266 Module.

Byork:
I still get the same exact error.

does strstr() compile?

perhaps there is a compiler setting to bring in the expanded library for the ESP8266

Aye, strstr compile perfectly with or without the added statements at the top which you provided earlier.