1
2
3
4
5
6
7
8
9
10
11
12
13
14
15
16
17
18
19
20
21
22
23
24
25
26
27
28
29
30
31
32
33
34
35
36
37
38
39
40
41
42
43
44
45
46
47
48
49
50
51
52
53
54
55
56
57
58
59
60
61
62
63
64
65
66
67
68
69
70
71
72
73
74
75
76
77
78
79
80
81
82
83
84
85
86
87
88
89
90
91
92
93
94
95
96
97
98
99
100
101
102
103
104
105
106
107
108
109
110
111
112
113
114
115
116
117
118
119
120
121
122
123
124
125
126
127
128
129
130
131
132
133
134
135
136
137
138
139
140
141
142
143
144
145
146
147
148
149
| /*
* malloc_play.c: bizzarro programma per studiare il comportamento delle system call
* malloc(), realloc() e free().
*
* versione 1.5 del 22/03/2018
*
* Programma sviluppato a supporto del laboratorio di
* Sistemi di Elaborazione dell'Informazione del corso di laurea
* in Informatica classe L-31 presso l'Universita` degli Studi di
* Genova, anno accademico 2017/2018.
*
* Copyright (C) 2013-2018 by Giovanni Chiola <chiolag@acm.org>
*
* This program is free software; you can redistribute it and/or modify
* it under the terms of the GNU General Public License as published by
* the Free Software Foundation; either version 2 of the License, or
* (at your option) any later version.
*/
#include<stdlib.h>
#include<stdio.h>
/*** Just playing with the malloc(), realloc(), free()
*** system calls in order to guess how memory management
*** is implemented on this machine. If you get SEGMENTATION
*** FAULT while addressing unallocated heap memory, just run
*** the program with different "min" and/or "max" values,
*** explicitly given on the command line through argv[]
*** NOTICE: the default values are appropriate for the 32bit systems
*** available in the labs ***/
int main(int argc, char**argv){
unsigned char *p, *q, *oldp;
int sz=1, min=-8, max=60;
if ( argc > 1 )
sscanf(argv[1],"%d",&sz);
if ( sz <= 0 )
sz = 1;
else if ( sz > 300 )
sz = 300;
if ( argc > 2 )
sscanf(argv[2],"%d",&min);
if ( min > -1 )
min = -1;
else if ( min < -50 )
min = -50;
if ( argc > 3 )
sscanf(argv[3],"%d",&max);
if ( max < sz )
max = sz;
else if ( max > (sz+100) )
max = sz+100;
printf("... allocating %d unsigned chars, min=%d, max=%d\n\n",sz,min,max);
p = (unsigned char*)malloc(sz);
if ( p == NULL ) {
printf("could not allocate p\n");
exit(0);
}
printf("*p=%hhu\n",*p);
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = 1 ; i <= max ; i++ )
printf("p[%d]=%hhu\n",i,p[i]);
}
printf("\n... allocating %d more unsigned chars to a different pointer\n\n",sz);
q = (unsigned char*)malloc(sz);
if ( q == NULL ) {
printf("could not allocate q\n");
exit(0);
}
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("q[%d]=%hhu\n",i,q[i]);
for ( i = 0 ; i <= max ; i++ )
printf("q[%d]=%hhu\n",i,q[i]);
}
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = 0 ; i <= max ; i++ )
printf("p[%d]=%hhu\n",i,p[i]);
}
sz += 10;
printf("\n... reallocating %d unsigned chars\n\n",sz);
oldp = p;
p = (unsigned char*)realloc((void*)p,sz);
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = 0 ; i <= max ; i++ )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = -1 ; i >= min ; i-- )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
for ( i = 0 ; i <= max ; i++ )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
}
sz += 15;
printf("\n... reallocating %d unsigned chars\n\n",sz);
p = (unsigned char*)realloc((void*)p,sz);
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = 0 ; i <= max ; i++ )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = -1 ; i >= min ; i-- )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
for ( i = 0 ; i <= max ; i++ )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
}
sz -= 25;
printf("\n... reallocating %d unsigned chars\n\n",sz);
p = (unsigned char*)realloc((void*)p,sz);
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = 0 ; i <= max ; i++ )
printf("p[%d]=%hhu\n",i,p[i]);
for ( i = -1 ; i >= min ; i-- )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
for ( i = 0 ; i <= max ; i++ )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
}
printf("\n... freeing p\n\n",sz);
free((void*)p);
{ int i;
for ( i = 0 ; i >= min ; i-- )
printf("p[%d]=%hhu\n",i,p[i]);
}
printf("\n... freeing q\n\n",sz);
free((void*)q);
{ int i;
for ( i = 0 ; i >= min ; i-- )
printf("q[%d]=%hhu\n",i,q[i]);
for ( i = -1 ; i >= min ; i-- )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
for ( i = 0 ; i <= max ; i++ )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
}
printf("\n... freeing oldp\n\n",sz);
free((void*)oldp);
{ int i;
for ( i = -1 ; i >= min ; i-- )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
for ( i = 0 ; i <= max ; i++ )
printf("oldp[%d]=%hhu\n",i,oldp[i]);
}
exit(0);
} |
(
