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CHC: update PO generation for Div and Mod #250

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Merged
sipma merged 1 commit into from
Jun 19, 2026
Merged

CHC: update PO generation for Div and Mod #250

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8 changes: 8 additions & 0 deletions CodeHawk/CHC/cchanalyze/cCHPOCheckIntOverflow.ml
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Original file line number Diff line number Diff line change
Expand Up @@ -1214,6 +1214,14 @@ object
end


(* C99 $6.5.5:
When integers are divided, the result of the / operator is the algebraic
quotient with any fractional part discarded.105) If the quotient a/b is
representable, the expression (a/b)*b + a%b shall equal a;

C11 $6.5.5 adds the following:
otherwise, the behavior of both a/b and a%b is undefined.*)

let check_int_overflow
?(unsigned=false)
(poq:po_query_int)
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23 changes: 12 additions & 11 deletions CodeHawk/CHC/cchpre/cCHPrimaryProofObligations.ml
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Expand Up @@ -315,22 +315,25 @@ and create_po_binop
^ " " ^ (p2s (current_loc_to_pretty loc))]
end

| Div ->
(* C99 $6.5.5:
When integers are divided, the result of the / operator is the algebraic
quotient with any fractional part discarded.105) If the quotient a/b is
representable, the expression (a/b)*b + a%b shall equal a;

C11 $6.5.5 adds the following:
otherwise, the behavior of both a/b and a%b is undefined.*)
| Div | Mod ->
begin
match fenv#get_type_unrolled t with
| TInt (ik, _) when is_signed_type ik ->
begin
add (PIntUnderflow (binop, e1, e2, ik));
add (PIntOverflow (binop, e1, e2, ik));
addxop (PNotZero e2) 2
end
| TInt (ik,_) ->
begin
add (PUIntUnderflow (binop, e1, e2, ik));
add (PUIntOverflow (binop, e1, e2, ik));
addxop (PNotZero e2) 2
end
| TFloat _ -> add (PNotZero e2)
| TInt _ ->
addxop (PNotZero e2) 2
| TFloat _ ->
add (PNotZero e2)
| _ ->
log_error_result
~tag:"create_po_binop"
Expand All @@ -344,8 +347,6 @@ and create_po_binop
^ " " ^ (p2s (current_loc_to_pretty loc))]
end

| Mod -> addxop (PNotZero e2) 2

| PlusPI | IndexPI | MinusPI ->
let tgttyp =
match fenv#get_type_unrolled t with
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