使用示例find.c文件，可以使用默认的alt-ergo毫无问题地证明它。但是，当更改为cvc4时，会出现警告消息和语法错误。这里的代码：
/*@ requires 0 <= n && \valid(a+(0..n-1));
assigns \nothing;
ensures (\result == -1 && ! (\exists int i; 0<=i<n && a[i] == v))
|| (0 <= \result < n && a[\result] == v);
*/
int find(int n,const int a[n],int v)
{
int i;
/*@ loop invariant 0<=i<=n;
loop invariant \forall int j; 0<=j<i ==> a[j] != v;
loop assigns i;
loop variant n - i;
*/
for (i=0; i<n; ++i)
if (a[i] == v)
return i;
return -1;
}
int main(void)
{
const int const a1[5] = { 9,7,8,9,6 };
int const f1 = find(5,a1,8);
return 0;
}
运行此命令并获取以下消息：
frama-c -wp -wp-prover CVC4 -wp-out out find.c
File "out/typed/find_Why3_ide.why", line 14, characters 0-20:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/find_Why3_ide.why", line 15, characters 0-28:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 6, characters 0-20:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 7, characters 0-18:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 8, characters 0-31:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 9, characters 0-25:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 10, characters 0-18:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 12, characters 0-18:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/Compound.why", line 13, characters 0-24:
warning: the keyword `import' is redundant here and can be omitted
File "out/typed/find_Why3_ide.why", line 17, characters 60-61:
syntax error
------------------------------------------------------------
[wp] [CVC4] Goal typed_find_loop_inv_2_preserved : Failed
Why3 exits with status 1.
[wp] [CVC4] Goal typed_find_loop_inv_preserved : Failed
Why3 exits with status 1.
[wp] [CVC4] Goal typed_find_post : Failed
Why3 exits with status 1.
[wp] Proved goals: 10 / 13
Qed: 10 (4ms)
CVC4: 0 (failed: 3)
如何摆脱警告和语法错误？我的CVC4是1.6版。