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Throw ArithmeticException whenever a division-by-zero is encountered #950

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Original file line number Diff line number Diff line change
@@ -0,0 +1,11 @@
public class ArithmeticExceptionTest {
public static void main(String args[]) {
try {
int i=0;
int j=10/i;
}
catch(ArithmeticException exc) {
assert false;
}
}
}
9 changes: 9 additions & 0 deletions regression/cbmc-java/ArithmeticException1/test.desc
Original file line number Diff line number Diff line change
@@ -0,0 +1,9 @@
CORE
ArithmeticExceptionTest.class
--java-throw-runtime-exceptions
^EXIT=10$
^SIGNAL=0$
^.*assertion at file ArithmeticExceptionTest.java line 8 function.*: FAILURE$
^VERIFICATION FAILED
--
^warning: ignoring
1 change: 1 addition & 0 deletions src/java_bytecode/java_bytecode_convert_method.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -1051,6 +1051,7 @@ codet java_bytecode_convert_methodt::convert_instructions(
i_it->statement=="checkcast" ||
i_it->statement=="newarray" ||
i_it->statement=="anewarray" ||
i_it->statement==patternt("?div") ||
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only idiv and ldiv throw ArithmeticException, fdiv and ddiv do not. In addition irem and lrem throw, too.

i_it->statement==patternt("?astore") ||
i_it->statement==patternt("?aload") ||
i_it->statement=="invokestatic" ||
Expand Down
37 changes: 37 additions & 0 deletions src/java_bytecode/java_bytecode_instrument.cpp
Original file line number Diff line number Diff line change
Expand Up @@ -57,6 +57,10 @@ class java_bytecode_instrumentt:public messaget
const exprt &idx,
const source_locationt &original_loc);

codet check_arithmetic_exception(
const exprt &denominator,
const source_locationt &original_loc);

codet check_null_dereference(
const exprt &expr,
const source_locationt &original_loc,
Expand Down Expand Up @@ -132,6 +136,32 @@ codet java_bytecode_instrumentt::throw_exception(
return init_code;
}


/// Checks whether there is a division by zero
/// and throws ArithmeticException if necessary.
/// Exceptions are thrown when the `throw_runtime_exceptions`
/// flag is set.
/// \return Based on the value of the flag `throw_runtime_exceptions`,
/// it returns code that either throws an ArithmeticException
/// or is a skip
codet java_bytecode_instrumentt::check_arithmetic_exception(
const exprt &denominator,
const source_locationt &original_loc)
{
symbolt exc_symbol;

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as only integral div-by-zero throws, maybe add invariant for java_int_type or java_long_type

const constant_exprt &zero=from_integer(0, denominator.type());
const binary_relation_exprt equal_zero(denominator, ID_equal, zero);

if(throw_runtime_exceptions)
return throw_exception(
equal_zero,
original_loc,
"java.lang.ArithmeticException");

return code_skipt();
}

/// Checks whether the array access array_struct[idx] is out-of-bounds,
/// and throws ArrayIndexOutofBoundsException/generates an assertion
/// if necessary; Exceptions are thrown when the `throw_runtime_exceptions`
Expand Down Expand Up @@ -463,6 +493,13 @@ codet java_bytecode_instrumentt::instrument_expr(
expr.op0(),
expr.source_location());
}
else if(expr.id()==ID_div)
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needs ID_mod, too, ID_rem is for float/double, if I understood correctly

{
// check division by zero
return check_arithmetic_exception(
expr.op1(),
expr.source_location());
}
else if(expr.id()==ID_member &&
expr.get_bool(ID_java_member_access))
{
Expand Down