Platformio Linker Error When Including <functional>

Question

I'm using PlatformIO (with the VS Code extension), on Windows 10, and am compiling for the Teensy 3.5 board.

I've reduced a linker error in one of my projects to the following piece of code:

#include <Arduino.h>
#include <functional>

void setup()
{
   // Serial.println();
  std::function<void()> func;
  func();
}

void loop() {}

When I try to compile and link this, it compiles fine, but fails to link. If i uncomment the Serial.println(), then it links and compiles.

I am using the following settings in the platformio.ini file:

[env:teensy35]
platform = teensy
board = teensy35
framework = arduino

The error it gives when failing to link is:

c:/users/zackh/.platformio/packages/toolchain-gccarmnoneeabi/bin/../lib/gcc/arm-none-eabi/5.4.1/../../../../arm-none-eabi/lib/armv7e-m/fpu\libc.a(lib_a-writer.o): In function _write_r': writer.c:(.text._write_r+0x12): undefined reference to_write' collect2.exe: error: ld returned 1 exit status

Any idea what's happening here?

Zack Zack · Accepted Answer · 2019-04-21T18:58:27

The solution I found was to include the following line in the platformio.ini project.

build_flags = -llibc -lc

Platformio Linker Error When Including <functional>

1 Answers