* Remove string duplication (search binary with string utility to find out how much space you can save)
  * Use integer error codes rather than showing error strings
  * Literal pool usage reduction  
      * e.g. when going from ARM to Thumb
      * group globals into structures
  * .sinit usage (construct instead simple global structs)
  * selectively enable optimization for some files
  * refactoring duplicate code
  * reduce usage of standard library functions


====== assertions ======
  #define ASSERT(expr) \
  if (expr)            \
      {}               \
  else                 \
      aFailed(F_NUM, __LINE__) 
        
  trap()
  {
      #ifndef NDEBUG
      #define _BKPT __ASM(“bkpt 0″)
      while(1);
      #endif
  }

http://blog.feabhas.com/2013/02/developing-a-generic-hard-fault-handler-for-arm-cortex-m3cortex-m4/

http://blog.frankvh.com/2011/12/07/cortex-m3-m4-hard-fault-handler/

http://www.drdobbs.com/an-exception-or-a-bug/184401686

http://www.embedded.com/electronics-blogs/other/4023329/Assert-Yourself

https://interrupt.memfault.com/blog/asserts-in-embedded-systems