This compiler is far from reaching the C99 standard. Less commonly used features like unions, the register keyword, goto statements, inline asm, and casting a non-constant to a constant pointer all cause this compiler to crash when identical code works perfectly on the gnu gcc compiler. The performance is very poor, even for a phone - all the variables might as well be volatile and none of the instructions may be optimized. If you purchase this app, keep in mind that it functions as a beginners introductory learning tool and that it cannot compile real code - like the gnu libc source code - that can compile in a fully functional compiler.