A15-0-4 - Unofficial Autosar C++ Guidelines Reference

Rule A15-0-4 (required, architecture / design /implementation, non-automated)

Unchecked exceptions shall be used to represent errors from which the caller cannot reasonably be expected to recover.

Rationale

Problems that are unpreventable and not expected by the caller are represented with instances of unchecked exceptions category. Such problems include: Software errors, i.e. preconditions/postconditions violations, arithmetic errors, failed assertions, sanity checks or invalid variable access, that in C++ are typically represented by logic_error, bad_exception, bad_cast and bad_typeid exceptions or their subclasses Internal errors of the executable (like VirtualMachineError of Java language), that in C++ are represented by bad_alloc and bad_array_new_length exceptions

It is not possible to recover from such errors in a meaningful way.

Example

//% $Id: A15-0-4.cpp 289436 2017-10-04 10:45:23Z michal.szczepankiewicz $
#include <cstdint>
#include <stdexcept>
#include <vector>
class InvalidArguments : public std::logic_error // Compliant - invalid
// arguments error is
// "unchecked" exception
{
public:
using std::logic_error::logic_error;
};
class OutOfMemory : public std::bad_alloc
Compliant - insufficient memory
error is "unchecked" exception
{
public:
using std::bad_alloc::bad_alloc;
};
class DivisionByZero : public std::logic_error
Compliant - division by zero
error is "unchecked"
exception
{
public:
using std::logic_error::logic_error;
};
class CommunicationError : public std::logic_error // Non-compliant // communication error
// should be "checked"
// exception but defined to be "unchecked"
{
public:
using std::logic_error::logic_error;
};
double Division(std::int32_t a, std::int32_t b) noexcept(false)
{
// ...
if (b == 0)

{
throw DivisionByZero(
"Division by zero error");
}

// Unchecked exception thrown correctly

// ...
}
void Allocate(std::uint32_t bytes) noexcept(false)
{
// ...
throw OutOfMemory(); // Unchecked exception thrown correctly
}
void InitializeSocket() noexcept(false)
{
bool validParameters = true;

// ...
if (!validParameters)
{
throw InvalidArguments("Invalid parameters passed"); // Unchecked
// exception
// thrown
// correctly

}
}
void SendData(std::int32_t socket) noexcept(false)
{
// ...
bool isSentSuccessfully = true;

// ...
if (!isSentSuccessfully)
{
throw CommunicationError("Could not send data"); // Unchecked exception
// thrown when checked
// exception should
// be.

}
}
void IterateOverContainer(const std::vector<std::int32_t>& container,
std::uint64_t length) noexcept(false)
{
for (std::uint64_t idx{0U}; idx < length; ++idx)
{
int32_t value = container.at(idx); // at() throws std::out_of_range
// exception
when passed integer
// exceeds the size of
container.
// Unchecked exception
thrown
// correctly
}
}

Unofficial Autosar C++ Guidelines Reference

Rationale

Example

See also