I am new to Assembler and am currently reading a book about it by Jonathan Bartlett called ‘Learn to Program with Assembly’. On pages 160-1 he gives the following sample program to demonstrate the use of the STDIN and STDOUT features of C/C++ in GAS Assembler:

.globl main

.section .data
    promptformat:   .ascii "Enter two numbers separated by spaces, then press RETURN.n"
    scanformat: .ascii "%d %d"
    resultformat:   .ascii "The result is %d.n"

.section .text
    .equ    LOCAL_NUMBER, -8
    .equ    LOCAL_EXPONENT, -16
main:
    enter $16, $0

    # PROMPT THE USER FOR INPUT
    movq stdout, %rdi
    movq $promptformat, %rsi
    movq $0, %rax
    call fprintf

    # READ IN DATA AND PERFORM CALCULATION
    movq stdin, %rdi
    movq $scanformat, %rsi
    leaq LOCAL_NUMBER(%rbp), %rdx
    leaq LOCAL_EXPONENT(%rbp), %rsi
    call exponent

    # OUTPUT RESULT FOR USER
    movq stdout, %rdi
    movq $resultformat, %rsi
    movq %rax, %rdx
    movq $0, %rax
    call fprintf

    leave
    ret

When I run the program, the STDOUT giving the prompt works just fine, but when I type in the two integers and hit ENTER, the program does nothing until I am forced to exit with Ctrl-C. It’s as though the program is waiting for some type of end-of-line character or something.

(NOTE: This program also calls another program named ‘exponent’ which is not shown here. If anyone thinks it’s necessary, I can post that code, too. Honestly, though, I don’t think the exponentscanf program is making it that far anyway.)

I am running Linux Mint-Virginia, and the program is being compiled with GNU: gcc -static exponentscanf.s exponentfunc.s -o exponentscanf.

[I think I just addressed this point above.]