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I was called a liar when I showed my output (while debugging a problem). So I thought I'll make it into a puzzle.

The output of this code

T a,b,c, d;
printf("%p %p %p %p %d %d %d %d %d", &a, &b, &c, &d, &a-&b, &b-&c, &c-&d, &b-&d, &a-&d);

Is this

0xbfe1327c 0xbfe13278 0xbfe132ac 0xbfe13274 1 -13 14 1 2

Why is the address of c so weird?

There is absolutely no cheating with T, in fact its defined as struct T {void* v; };

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closed as off topic by dmckee Nov 10 '12 at 12:21

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What's weird about it? Just because the compiler didn't allocate c next to a,b, and d in the stack frame doesn't make it weird. The compiler probably allocates variables is some arbitrary order (by the order they appear in some compile-time hash table, maybe). What other variables are there in the function? – Keith Randall Nov 10 '12 at 6:32
@KeithRandall: Only those 4. I can also choose which variable has a weird address. It involves one line inside of this function (which is hidden atm) – acidzombie24 Nov 10 '12 at 6:49
Related to and; and utterly inappropriate for CodeGolf.SE. Learning to construct your own complete, compact, compilable example will help you become a better debugger. – dmckee Nov 10 '12 at 12:28
@dmckee: fyi i already fixed the code, every post i made had info to see the actual problem and all the code I written was standard C++ and I already knew the issue was stack related while everyone thought it was something else. The problem was a C optimization which didnt like calling C ++ code. I had to add data to the generated C files to fix it. – acidzombie24 Nov 10 '12 at 18:16
up vote 1 down vote accepted

Not exactly the same, but a similar effect:

typedef struct T {void* v; } T;
#define printf { T c; printf

    T a,b,c, d;
    printf("%p %p %p %p %d %d %d %d %d", &a, &b, &c, &d, &a-&b, &b-&c, &c-&d, &b-&d, &a-&d);

}   return 0;


0xbfd4034c 0xbfd40348 0xbfd40340 0xbfd40344 1 2 -1 1 
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Good enough. I accepted. Here is the solution I came up with – acidzombie24 Nov 10 '12 at 18:17

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