130 lines
4.6 KiB
C
130 lines
4.6 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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/* This program allows us to visualize the layout of a
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* process in memory, printing the addresses of
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* various parts of the program, including components
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* in the text, data, and bss segments as well as on
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* the heap and the stack.
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*/
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#include <err.h>
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#include <stdio.h>
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#include <stdlib.h>
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#include <unistd.h>
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#define ARRAY_SIZE 16
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#define MALLOC_SIZE 32
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#define MSG "I'm a constant, wheeee!"
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char array[ARRAY_SIZE];
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char *string = "a string";
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char *string2;
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int num = 10;
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int num2;
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extern char **environ;
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void func(void);
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void func2(const char *);
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int
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main(int argc, char **argv) {
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int var;
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char *ptr;
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char func_array[ARRAY_SIZE];
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(void)printf("High address (args and env):\n");
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(void)printf("----------------------------\n");
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(void)printf("environ[0] at : 0x%12lX\n", (unsigned long)environ);
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(void)printf("last arg at : 0x%12lX\n", (unsigned long)&argv[argc]);
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(void)printf("first arg at : 0x%12lX\n", (unsigned long)&argv[0]);
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(void)printf("\n");
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(void)printf("Stack:\n");
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(void)printf("------\n");
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(void)printf("First variable inside main at : 0x%12lX\n", (unsigned long)&var);
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(void)printf("func_array[] ends at : 0x%12lX\n", (unsigned long)&func_array[ARRAY_SIZE]);
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(void)printf("func_array[] (like 'array[]', but on stack) begins at : 0x%12lX\n", (unsigned long)&func_array[0]);
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(void)printf("argc at : 0x%12lX\n", (unsigned long)&argc);
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(void)printf("argv at : 0x%12lX\n", (unsigned long)&argv);
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func2("from main");
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func();
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(void)printf("\n");
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(void)printf("Heap:\n");
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(void)printf("-----\n");
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if ((ptr = malloc(MALLOC_SIZE)) == NULL) {
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err(EXIT_FAILURE, "unable to allocate memory");
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/* NOTREACHED */
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}
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(void)printf("malloced area ends at : 0x%12lX\n", (unsigned long)ptr+MALLOC_SIZE);
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(void)printf("malloced area begins at : 0x%12lX\n", (unsigned long)ptr);
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free(ptr);
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(void)printf("\n");
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(void)printf("Uninitialized Data (BSS):\n");
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(void)printf("-------------------------\n");
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(void)printf("array[] ends at : 0x%12lX\n", (unsigned long)&array[ARRAY_SIZE]);
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(void)printf("array[] (uninitialized, fixed-size char * on BSS) from : 0x%12lX\n", (unsigned long)&array[0]);
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(void)printf("num2 (uninitialized global int) at : 0x%12lX\n", (unsigned long)&num2);
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(void)printf("string2 (uninitialized global char *) at : 0x%12lX\n", (unsigned long)&string2);
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(void)printf("extern **environ at : 0x%12lX\n", (unsigned long)&environ);
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(void)printf("\n");
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(void)printf("Initialized Data:\n");
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(void)printf("-----------------\n");
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(void)printf("num (initialized global int) at : 0x%12lX\n", (unsigned long)&num);
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(void)printf("string (initialized global char *) at : 0x%12lX\n", (unsigned long)&string);
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(void)printf("\n");
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(void)printf("Text Segment:\n");
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(void)printf("-------------\n");
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(void)printf("func2 (function) at : 0x%12lX\n", (unsigned long)&func2);
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(void)printf("func (function) at : 0x%12lX\n", (unsigned long)&func);
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(void)printf("main (function) at : 0x%12lX\n", (unsigned long)&main);
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(void)printf("\n");
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return EXIT_SUCCESS;
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}
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void
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func() {
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int fint;
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/* Change this value to 0 and note how
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* the location of where it is stored
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* changes from the Data to BSS segment. */
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static int n = 1;
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(void)printf("func frame at : 0x%12lX\n", (unsigned long)&fint);
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(void)printf("static int n within func at : 0x%12lX\n", (unsigned long)&n);
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n++;
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func2("from func");
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}
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void
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func2(const char *how) {
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int fint;
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(void)printf("func2 (%s): frame at : 0x%12lX\n", how, (unsigned long)&fint);
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}
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