High level macro not recognized - Beginner MASM

Question

main proc
 finit
 .while ang < 91
    invoke func, ang
    fstp res
    print real8$(ang), 13, 10
    print real8$(res), 13, 10
    fld ang
    fld1
    fadd
    fstp ang
 .endw
 ret
main endp

What's wrong with this piece of MASM code?

I get an error on .endw. I have ran some tests to ensure myself of that. Assembler tells me invalid instruction operands.

Thank you for your time!

Answer 1

Remember that masm is a "typed" assembly language. And it looks like ang is defined as a real.

Problem is, ".while" generate a cmp instruction followed by a conditional jump. And a cmp instruction takes some integer value from either a reg or memory, but certainly not a real. Thus the "invalid instruction operand" error.

The reason this happens in the .endw is most likely because the .while / .endw construct generates its test at the bottom of the loop rather than at the beginning.