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# [Frama-c-discuss] multiple functions, why error

• Subject: [Frama-c-discuss] multiple functions, why error
• From: Christoph.Weber at first.fraunhofer.de (Christoph Weber)
• Date: Wed, 7 Jan 2009 16:10:40 +0100

```Hello, now I have a rather complex example, which I need some advice with before posting it on the BTS

The function reverse uses a swap function to reverse the elements of an array:

#include "swap.h"
/*@
requires 0 <= length;
requires \valid_range (a, 0, length-1);
ensures \forall integer k; 0 <= k < length ==>
\old(a[k]) == a[length-1-k] &&
a[k] == \old(a[length-1-k]);
*/
void reverse_array (int* a, int length)
{
int index_a = 0;
int index_backwards = length;

/*@
loop invariant 0 <= index_a <= length;
loop invariant 0 <= index_backwards <= length;
loop invariant index_a == length - index_backwards;

loop invariant \forall integer k; 0 <= k < index_a ==> \at(a[k],Pre) == a[length-1-k] &&
a[k] == \at(a[length-1-k],Pre);
*/
while ((index_a != index_backwards) && (index_a != --index_backwards))
swap_user (&a[index_a++], &a[index_backwards]);
}

File "swap.h"
========
/*@
requires \valid(a);
requires \valid(b);
ensures *a == \old(*b);
ensures *b == \old(*a);
*/
void swap_user (int* a, int* b );

File "swap.c"
========
#include "swap.h"
void swap_user (int* a, int* b )
{
int c = *a;
*a = *b;
*b = c;
}

When invoking the Gui for reverse_array()
I get the error:
Cleaning unused parts
Starting semantical analysis
Starting Jessie translation
No code for function swap_user, default assigns generated
Producing Jessie files in subdir reverse_array.jessie
File reverse_array.jessie/reverse_array.jc written.
File reverse_array.jessie/reverse_array.cloc written.
Calling Jessie tool in subdir reverse_array.jessie
Generating Why function reverse_array
Calling VCs generator.
make[1]: Entering directory `/cygdrive/d/Eigene Dateien/StudienUnterlagen/Praxis
semester/SVN/trunk/Framac/own-examples/ProvableSTL/reverse/reverse_array.jessie'

gwhy-bin [...] why/reverse_array.why
Computation of VCs...
File "why/reverse_array.why", line 1158, characters 101-117:
Application to int_P_int_M_a_22 creates an alias
make[1]: *** [reverse_array.stat] Error 1
make[1]: Leaving directory `/cygdrive/d/Eigene Dateien/StudienUnterlagen/Praxiss
emester/SVN/trunk/Framac/own-examples/ProvableSTL/reverse/reverse_array.jessie'
Jessie subprocess failed: make -f reverse_array.makefile gui

I would like to know whether the mistake is mine or if I have to post on the BTS

Cheers Christoph

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