Memory location of variable

Code:

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#include <stdio.h>
int main()
{
    int i=3;
    float j=1.5;
    char k='c';
    printf("%u, %u, %u\n", &i, &j, &k);
    return 0;
}

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My book said the memory location of these variables is contiguous. But I have got like below :

Code:

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3216967268, 3216967272, 3216967279

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And three warnings :

Code:

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gcc -Wall -o "untitled1" "untitled1.c" (in directory: /home/duh/Desktop/C)
untitled1.c: In function ‘main’:
untitled1.c:7:2: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 2 has type ‘int *’ [-Wformat]
untitled1.c:7:2: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 3 has type ‘float *’ [-Wformat]
untitled1.c:7:2: warning: format ‘%u’ expects argument of type ‘unsigned int’, but argument 4 has type ‘char *’ [-Wformat]
Compilation finished successfully.

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How to avoid these error message?

Thanks.

Quote:

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Originally Posted by justine

My book said the memory location of these variables is contiguous.

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Your book makes an assumption that is not necessarily true.

Quote:

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Originally Posted by justine

And three warnings :

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That is because the correct specifier to use to print pointers to void is %p, e.g.,

Code:

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printf("%p, %p, %p\n", (void*)&i, (void*)&j, (void*)&k);

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Quote:

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Your book makes an assumption that is not necessarily true.

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Can you please explain it? You said the book is wrong, or it may be because of my 32 bit compilar?

Your book is wrong because the memory locations for those variables are not guaranteed to be contiguous.

Ok, Thank you.

Please tell us the book.

It is Let Us C by YPK. But I thing it is not specifying that it will be contiguous, but during a program for showing the increase of memory location by one it point to the next location of its type, He gives :
First address of int=65524
First address of float=65520
First address of char=65519
Final address of int=65528
Final address of float=65524
Final address of char=65520

May be I misunderstood this.

Hope you get me. Not good at english.

It's not guaranteed to be increasing in memory. The compiler is free to allocate variables in any order. It's not specified in the C standard how a compiler translates user code into machine instructions and absolute addresses. Only that for an array, its elements are contiguous in memory and therefore pointer arithmetic is allowed.

Furthermore, modern compilers often randomize the variable locations on purpose for security reasons. Read more here: Address space layout randomization - Wikipedia, the free encyclopedia.

Quote:

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Let Us C by YPK

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I figured as much. That book is well-known to be crap.