Linker fails to find memchr implementation

When I try to use memchr function in my application, I get the following error during build:

Linking .pioenvs\esp01_1m\firmware.elf
.pioenvs\esp01_1m\lib\libESPAsyncWebServer_ID306.a(WebResponses.o):(.text._ZN17AsyncFileResponse11_fillBufferEPhj+0x0): undefined reference to `memchr'
.pioenvs\esp01_1m\lib\libESPAsyncWebServer_ID306.a(WebResponses.o):(.text._ZN17AsyncFileResponse11_fillBufferEPhj+0x59): undefined reference to `memchr'
.pioenvs\esp01_1m\lib\libESPAsyncWebServer_ID306.a(WebResponses.o): In function `AsyncFileResponse::_fillBuffer(unsigned char*, unsigned int)':
WebResponses.cpp:(.text._ZN17AsyncFileResponse11_fillBufferEPhj+0x2c3): undefined reference to `memchr'
WebResponses.cpp:(.text._ZN17AsyncFileResponse11_fillBufferEPhj+0x302): undefined reference to `memchr'

The platform is Arduino for ESP8266.
Isn’t memchr included in standard C library for this platform?

Hi @azarubkin!
Does your example work in Arduino IDE?

@valeros No, it gives the same error.

I would recommend to find a memchr implementation (e.g.this one) and add it to a file somewhere in your project.