title: exit.c:(.text+0x18): undefined reference to `_exit' when using arm-none-eabi-gcc
body: <p>I'm new to the field of microcontrollers. I need to port an IDE which is compiling programs for AVR microcontrollers to compile programs for ARM microcontrollers. I have just replaced the compiler from AVR to ARM and added some options as told by someone.
  The following is the command:</p>
  
  <pre><code>\ARM-GCC\bin\arm-none-eabi-gcc -O0 -ffunction-sections -Wall -std=gnu99 -mfloat-abi=soft 
  -Wa,-adhlns="$@.lst" -fmessage-length=0 -mcpu=cortex-m0 -mthumb -g3 -gdwarf-2 -Wl,
  --gc-sections -o &lt;Dir_name&gt;\Build_Files\Blink_arm.cpp.elf  &lt;Dir_name&gt;\Build_Files\Blink_arm.cpp.o &lt;Dir_name&gt;\Build_Files\core.a 
  -L&lt;Dir_name&gt;\Build_Files -lm 
  </code></pre>
  
  <p>When I execute it I get the follwing error:</p>
  
  <pre><code>tools/arm-gcc/bin/../lib/gcc/arm-none-eabi/4.6.2\libc.a(lib_a-exit.o): In function `exit':
  exit.c:(.text+0x18): undefined reference to `_exit'  
  collect2: ld returned 1 exit status
  </code></pre>
  
  <p>May I get some help on what is this error and how can I solve it. And also I don't know what those options in the command line specify.</p>