73 lines
1.4 KiB
C
73 lines
1.4 KiB
C
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/* This file is part of the sample code and exercises
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* used by the class "Advanced Programming in the UNIX
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* Environment" taught by Jan Schaumann
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* <jschauma@netmeister.org> at Stevens Institute of
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* Technology.
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*
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* This file is in the public domain.
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*
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* You don't have to, but if you feel like
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* acknowledging where you got this code, you may
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* reference me by name, email address, or point
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* people to the course website:
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* https://stevens.netmeister.org/631/
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*/
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/* Use this program to illustrate how the
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* call stack works by inspecting the various
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* registers using gdb(1).
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*
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* Also inspect the return values of the
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* differrent functions and how the behavior
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* changes when you exit versus return
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* from main.
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*
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* Note that you have to compile without
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* warnings since we don't (explicitly)
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* return in 'sum2'.
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*
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* cc -g sum.c
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* gdb a.out
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* display $rbp
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* display $rsp
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* display $rip
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* display $rax
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* break __start
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* break main
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* break sum
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* break sum2
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* run
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*
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* Also use this example to illustrate that
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* you can manipulate both variables and
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* registers while the program is running.
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*/
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#include <stdio.h>
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#include <stdlib.h>
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int
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sum1(int a, int b) {
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int sum;
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sum = a + b;
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return sum;
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}
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int
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sum2(int a, int b) {
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int sum = a + b;
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printf("sum2: %d\n", sum);
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}
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int
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main() {
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int a = 1;
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int b = 2;
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a += b;
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printf("sum1 returned: %d\n", sum1(a, b));
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printf("sum2 returned: %d\n", sum2(b, a));
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return(0);
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//exit(0);
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}
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