Why is this an issue?
If a pointer to an object is used as an exception, the code that will catch the exception may or may not have to delete the pointed-to object. This
is even more complex in the exception case than in classical manual memory management, because of the distance between the throw
statements and the matching catch.
Throwing by value is just simpler and less error prone.
Noncompliant code example
class E { /* Implementation */};
E globalException;
void fn ( int i )
{
// In this situation, the developer writing the 'catch' has no way to know if the object pointed-to by
// the exception should be deleted or not...
if ( i > 10 ) {
throw ( &globalException); // Noncompliant, the catch is supposed not to delete the pointer
}
else {
throw (new E ); // Noncompliant, the catch is supposed to delete the pointer
}
}
Compliant solution
class E { /* Implementation */};
E globalException;
void fn ( int i )
{
if ( i > 10 ) {
throw ( globalException); // Throws a copy of the global variable
}
else {
throw (E{} ); // Throws a new object
}
}
Resources
- MISRA C++ 2008, 15-0-2 - An exception object should not have pointer type.
