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Try stepping through the code


  Value and type of last evaluated expression: Address of array element: Address of array elementx:  (none)

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Code

 Header...

typedef struct wotsit {
  float val;
  char *str;
  int length;
}Wotsit;


 Wotsit* newwotsit(int len){
»  Wotsit *w;

»  w=xmalloc(sizeof *w);

»  w->length=len;
»  w->val=0;
»  w->str=xmalloc(w->length);
»  return w;
}
 ... 


 int main(){
»  Wotsit *william;

»  william=newwotsit(20);
»  snprintf(william->str, william->length, 
    "Hello, world\n");
»  return 0;
}
 ...
Memory

Allocated memory

128
129
130
131
132
133
134
135
128.val = 4.90576264e+33
128.str = 1932826409
136
137
138
139
128.length = 1612158611

144
145
146
147
148
149
150
151
'Y' '>' ' ' ' ' ' ' ' ' ' ' 'r'
152
153
154
155
156
157
158
159
' ' ' ' ' ' ' ' '$' ' ' 'N' ' '
160
161
162
163
'b' '4' 'z' '~'

newwotsit()

296
297
298
299
300
301
302
303
w = 376
?
?
?
?
336
337
338
339
len = 20

main()

360
361
362
363
william = -1763361458

NB: the actual memory address of each variable is the
address shown plus 4290090464 (0xFFB595E0).

The actual address of allocated memory is the
address shown plus 161276144 (0x99CE0F0).

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