Compiled some source with the Arduino IDE and, at the end of compilation, the following loader errors appear:
/home/digysol/arduino-1.8.0/hardware/tools/arm/bin/../lib/gcc/arm-none-eabi/4.8.4/../../../../arm-none-eabi/lib/armv7e-m/libc.a(lib_a-openr.o): In function _open_r': openr.c:(.text._open_r+0x10): undefined reference to
_open'
/home/digysol/arduino-1.8.0/hardware/tools/arm/bin/../lib/gcc/arm-none-eabi/4.8.4/../../../../arm-none-eabi/lib/armv7e-m/libc.a(lib_a-writer.o): In function _write_r': writer.c:(.text._write_r+0x10): undefined reference to
_write'
collect2: error: ld returned 1 exit status
Welcome any suggestions as to what in the source could have triggered this error.