How to type EOF in ARMv8 Assembly?

Question

I am using the ARMv8 instruction set with Aarch64 execution state. The problem I am having, is were supposed to translate C code into assembly, and I am stuck on the following:

while (c != '\n' && c != EOF)
    c = getchar();

I know the basic setup for the while loop, as well as how to test c != '\\n' but the issue I have is how to write EOF in assembly. Can i just type

cmp c_r, EOF
b.eq skipwhile

or is it something else?

Answer 1

It depends on what code you're using in assembly for getchar() -

• If you're just using a call to the assembly version of standard C library getchar() , then you can test with the C library's definition of EOF - normally -1 .
• If you're implementing your own getchar() in assembly, then you need to match your test to the return value of your getchar() implementation when it gets to the end-of-file.