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[Frama-c-discuss] Value Analysis: signed_overflow in addition to division_by_zero warning

On Mon, Jan 27, 2014 at 2:41 PM, Marcel Gehrke
<marcel.gehrke at tu-harburg.de>wrote:

>   /*@ assert Value: division_by_zero: x ? 0; */
>   h = 1 / x;
>   if (x != 0)
>     /*@ assert Value: division_by_zero: x ? 0; */
>     h = 1 / x;
>   else
>     /*@ assert Value: division_by_zero: x ? 0; */
>     /*@ assert Value: signed_overflow: 1/x ? 2147483647; */
>     /*@ assert Value: signed_overflow: -2147483648 ? 1/x; */

...
>

Actually, on the program you provided and with the command below, I get the
result visible after the fold.
There are way to many alarms in there. We will need to investigate. Thanks
for the report.

The previous Oxygen version did not duplicate the ?division by zero?
assertions but did generate the useless ?signed overflow? assertions.

Pascal
___________

~/frama-c-Fluorine-20130601 $ bin/toplevel.byte -val -main f1 ../t.c -print
[kernel] warning: cannot load 5 plug-ins (incompatible with
Fluorine-20130601).
                  Aorai; Obfuscator; Report; Security_slicing;
                  Wp
[kernel] preprocessing with "gcc -C -E -I.  ../t.c"
[value] Analyzing a complete application starting at f1
[value] Computing initial state
[value] Initial state computed
[value] Values of globals at initialization
../t.c:5:[value] Assertion got status unknown.
../t.c:6:[kernel] warning: division by zero: assert x ? 0;
../t.c:6:[value] assigning non deterministic value for the first time
../t.c:8:[value] Assertion got status unknown.
../t.c:11:[value] Assertion got status invalid (stopping propagation).
../t.c:9:[kernel] warning: division by zero: assert x ? 0;
[value] Recording results for f1
[value] done for function f1
[value] ====== VALUES COMPUTED ======
[value] Values at end of function f1:
          h ? {-1; 0; 1}
/* Generated by Frama-C */
void f1(int x)
{
  int h;
  /*@ assert Value: division_by_zero: x ? 0; */ ;
  /*@ assert Value: division_by_zero: x ? 0; */
  h = 1 / x;
  if (x != 0) {
    /*@ assert Value: division_by_zero: x ? 0; */ ;
    /*@ assert Value: division_by_zero: x ? 0; */
    h = 1 / x;
  }
  else {
    /*@ assert Value: division_by_zero: x ? 0; */ ;
    /*@ assert Value: signed_overflow: 1/x ? 2147483647; */ ;
    /*@ assert Value: signed_overflow: -2147483648 ? 1/x; */ ;
    h = 1 / x;
  }
  return;
}
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