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| ID | Project | Category | View Status | Date Submitted | Last Update |
| 0001117 | Frama-C | Plug-in > wp | public | 2012-03-12 11:04 | 2012-11-06 21:23 |
|
| Reporter | Jochen | |
| Assigned To | pherrmann | |
| Priority | normal | Severity | tweak | Reproducibility | always |
| Status | closed | Resolution | fixed | |
| Platform | | OS | | OS Version | |
| Product Version | Frama-C Nitrogen-20111001 | |
| Target Version | | Fixed in Version | Frama-C Oxygen-20120901 | |
|
| Summary | 0001117: addr_eq versus = and <> in generated axioms access_update, access_update_neq |
| Description | I ran "frama-c -wp -cpp-command 'gcc -C -E -I.' -pp-annot -wp-rte -wp-proof alt-ergo -no-unicode -wp-warnings -wp-out ./out ftest.c" on the attached program and inspected the generated file "out/store_ftest_post_1_po_ergo.why".
In the proof obligation for c-source line 14, the update operator a[i<-v] is used with e.g. addr_shift(s_0,0) substituted for i. In the axioms access_update and access_update_neq, arguments at position i are compared by built-in equality (and disequality <>).
However, terms starting with "addr_shift" are usually compared by "addr_eq", e.g. in the translation of lemma l.
I suggest to check whether the mentioned axioms should be weakened to:
axiom access_update : (forall a:'a1 farray.(forall i:int.(forall j:int.(forall v:'a1.(addr_eq(i,j) -> a[i<-v][j]=v)))))
axiom access_update_neq : (forall a:'a1 farray.(forall i:int.(forall j:int.(forall v:'a1.((not addr_eq(i,j)) -> (a[i<-v][j]=a[j]))))))
If not, I suggest to check whether addr_eq is in fact the same as =, and to drop the former for sake of simplicity. |
| Tags | No tags attached. |
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| Attached Files |  ftest.c [^] (243 bytes) 2012-03-12 11:04 [Show Content] [Hide Content]
/*@ lemma l:
\forall int* b; \forall integer i,j;
&b[i] == &b[j] ==> i == j;
*/
struct _str {
int a;
int b;
};
/*@
requires \valid(s);
ensures s->a == 0;
*/
void ftest(struct _str *s) {
s->a = 0;
s->b = 0;
}
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