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Merge pull request #6277 from feliperodri/struct-members-history
Adds support for struct members in history variables
2 parents 25ed175 + 21622a9 commit 61fd24d

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+195
-12
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10 files changed

+195
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‎doc/cprover-manual/contracts-history-variables.md‎

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Original file line numberDiff line numberDiff line change
@@ -13,8 +13,9 @@ _ensures_ clause.
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### Parameters
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`__CPROVER_old` takes a single argument, which is the identifier corresponding to
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a parameter of the function. For now, only scalar or pointer types are supported.
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`__CPROVER_old` takes a single argument, which is the identifier
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corresponding to a parameter of the function. For now, only scalars,
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pointers, and struct members are supported.
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### Semantics
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‎regression/contracts/history-pointer-enforce-09/main.c‎

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#include <stdlib.h>
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struct pair
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{
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int x;
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int y;
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};
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9+
void foo(struct pair *p) __CPROVER_assigns(p->y)
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__CPROVER_ensures(p->y == __CPROVER_old(p->y) + 5)
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{
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p->y = p->y + 5;
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}
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int main()
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{
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struct pair *p = malloc(sizeof(*p));
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p->x = 2;
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p->y = 2;
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foo(p);
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return 0;
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}

‎regression/contracts/history-pointer-enforce-09/test.desc‎

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CORE
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main.c
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--enforce-all-contracts
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^EXIT=0$
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^SIGNAL=0$
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^\[postcondition.\d+\] file main.c line \d+ Check ensures clause: SUCCESS$
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^\[foo.\d+\] line \d+ Check that p\-\>y is assignable\: SUCCESS$
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^VERIFICATION SUCCESSFUL$
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--
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--
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This test checks that history variables are supported for struct members.
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By using the --enforce-all-contracts flag, the post-condition (which contains
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the history variable) is asserted. In this case, this assertion should pass.

‎regression/contracts/history-pointer-enforce-10/main.c‎

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#include <assert.h>
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#include <stdlib.h>
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struct pair
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{
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int x;
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int *y;
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};
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int z = 5;
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int w[10] = {0};
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void foo(struct pair *p) __CPROVER_assigns(*(p->y), z)
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__CPROVER_ensures(*(p->y) == __CPROVER_old(*(p->y)) + __CPROVER_old(z))
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{
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*(p->y) = *(p->y) + z;
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z = 10;
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}
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void bar(struct pair *p) __CPROVER_assigns(p->y)
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__CPROVER_ensures(p->y == __CPROVER_old(p->y) + 5)
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{
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p->y = (p->y + 5);
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}
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void baz(struct pair p) __CPROVER_assigns(p)
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__CPROVER_ensures(p == __CPROVER_old(p))
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{
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struct pair pp = p;
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struct pair empty = {0};
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p = empty;
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p = pp;
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}
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int main()
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{
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struct pair *p = malloc(sizeof(*p));
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p->y = malloc(sizeof(*(p->y)));
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p->x = 2;
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*(p->y) = 2;
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foo(p);
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assert(*(p->y) == 7);
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p->y = w;
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w[5] = -1;
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bar(p);
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assert(*(p->y) == -1);
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baz(*p);
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return 0;
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}

‎regression/contracts/history-pointer-enforce-10/test.desc‎

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CORE
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main.c
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--enforce-all-contracts
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^EXIT=0$
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^SIGNAL=0$
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^\[postcondition.\d+\] file main.c line \d+ Check ensures clause\: SUCCESS$
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^\[postcondition.\d+\] file main.c line \d+ Check ensures clause\: SUCCESS$
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^\[postcondition.\d+\] file main.c line \d+ Check ensures clause\: SUCCESS$
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^\[bar.\d+\] line \d+ Check that p\-\>y is assignable\: SUCCESS$
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^\[baz.\d+\] line \d+ Check that pp is assignable\: SUCCESS$
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^\[baz.\d+\] line \d+ Check that empty is assignable\: SUCCESS$
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^\[baz.\d+\] line \d+ Check that p is assignable\: SUCCESS$
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^\[baz.\d+\] line \d+ Check that p is assignable\: SUCCESS$
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^\[foo.\d+\] line \d+ Check that \*p\-\>y is assignable\: SUCCESS$
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^\[foo.\d+\] line \d+ Check that z is assignable\: SUCCESS$
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^\[main.assertion.\d+\] line \d+ assertion \*\(p\-\>y\) == 7\: SUCCESS$
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^\[main.assertion.\d+\] line \d+ assertion \*\(p\-\>y\) == -1\: SUCCESS$
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^VERIFICATION SUCCESSFUL$
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--
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--
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This test checks that history variables are supported for structs, symbols, and
22+
struct members. By using the --enforce-all-contracts flag, the postcondition
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(with history variable) is asserted. In this case, this assertion should pass.

‎regression/contracts/history-pointer-enforce-11/main.c‎

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#include <stdlib.h>
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struct pair
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{
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int x;
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int y;
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};
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void foo(struct pair *p) __CPROVER_assigns(p->y)
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__CPROVER_ensures((p != NULL) == > (p->y == __CPROVER_old(p->y) + 5))
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__CPROVER_ensures((p == NULL) == > (p->y == __CPROVER_old(p->y)))
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{
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if(p != NULL)
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p->y = p->y + 5;
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}
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int main()
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{
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struct pair *p = NULL;
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foo(p);
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return 0;
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}

‎regression/contracts/history-pointer-enforce-11/test.desc‎

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KNOWNBUG
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main.c
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--enforce-all-contracts
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^EXIT=0$
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^SIGNAL=0$
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^\[postcondition.\d+\] Check ensures clause\: SUCCESS$
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^\[foo.\d+\] line \d+ Check that p\-\>y is assignable\: SUCCESS$
8+
^VERIFICATION SUCCESSFUL$
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--
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--
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This test checks that history variables handle NULL pointers.
12+
History variables currently do not check for nullness while
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storing values of objects, which may lead to NULL pointer dereferences.

‎regression/contracts/history-pointer-replace-04/main.c‎

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#include <stdlib.h>
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3+
struct pair
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{
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int x;
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int y;
7+
};
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9+
void foo(struct pair *p) __CPROVER_requires(p != NULL) __CPROVER_assigns(p->y)
10+
__CPROVER_ensures(p->y == __CPROVER_old(p->y) + 5)
11+
{
12+
p->y = p->y + 5;
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}
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15+
int main()
16+
{
17+
struct pair *p = malloc(sizeof(*p));
18+
p->x = 2;
19+
p->y = 2;
20+
foo(p);
21+
assert(p->y != 7);
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23+
return 0;
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}

‎regression/contracts/history-pointer-replace-04/test.desc‎

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@@ -0,0 +1,14 @@
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CORE
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main.c
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--replace-all-calls-with-contracts
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^EXIT=10$
5+
^SIGNAL=0$
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^\[precondition.\d+\] file main.c line \d+ Check requires clause\: SUCCESS$
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^\[main.assertion.\d+\] line \d+ assertion p\-\>y \!\= 7\: FAILURE$
8+
^VERIFICATION FAILED$
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--
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--
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This test checks that history variables are supported for struct members.
12+
By using the --replace-all-calls-with-contracts flag, the assertion in
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main should consider the ensures clause (with old value). In this case,
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this assertion should fail.

‎src/goto-instrument/contracts/contracts.cpp‎

Lines changed: 9 additions & 10 deletions
Original file line numberDiff line numberDiff line change
@@ -394,23 +394,22 @@ void code_contractst::replace_old_parameter(
394394

395395
const auto &parameter = to_old_expr(expr).expression();
396396

397-
// TODO: generalize below
398-
if(parameter.id() == ID_dereference)
397+
if(
398+
parameter.id() == ID_dereference || parameter.id() == ID_member ||
399+
parameter.id() == ID_symbol)
399400
{
400-
const auto &dereference_expr = to_dereference_expr(parameter);
401-
402-
auto it = parameter2history.find(dereference_expr);
401+
auto it = parameter2history.find(parameter);
403402

404403
if(it == parameter2history.end())
405404
{
406405
// 1. Create a temporary symbol expression that represents the
407406
// history variable
408407
symbol_exprt tmp_symbol =
409-
new_tmp_symbol(dereference_expr.type(), location, mode).symbol_expr();
408+
new_tmp_symbol(parameter.type(), location, mode).symbol_expr();
410409

411410
// 2. Associate the above temporary variable to it's corresponding
412411
// expression
413-
parameter2history[dereference_expr] = tmp_symbol;
412+
parameter2history[parameter] = tmp_symbol;
414413

415414
// 3. Add the required instructions to the instructions list
416415
// 3.1 Declare the newly created temporary variable
@@ -419,11 +418,11 @@ void code_contractst::replace_old_parameter(
419418
// 3.2 Add an assignment such that the value pointed to by the new
420419
// temporary variable is equal to the value of the corresponding
421420
// parameter
422-
history.add(goto_programt::make_assignment(
423-
tmp_symbol, dereference_expr, location));
421+
history.add(
422+
goto_programt::make_assignment(tmp_symbol, parameter, location));
424423
}
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426-
expr = parameter2history[dereference_expr];
425+
expr = parameter2history[parameter];
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}
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else
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{

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