CODEWITHSUNDEEP
c++
q0987
q0987

Reputation: 35982

Exception Specification more or less restrictive

Based on this

Incidentally, you can do this kind of assignment of a pointer to a function as long as the target’s exception specification is no more restrictive than the source’s

class A{};
class B{};
class C{};

void f() throw(A,B,C) {}

void (*pf)() throw(A,B);

int main()
{
    pf = f; // pf is more restrictive than that of f. I expect an error here!
}

The last statement should not pass the compiler. However, I have tried VS2010 and GCC latest version. Neither or them complain about it.

Question> Why?

Upvotes: 0

Views: 104

Answers (2)

NPE
NPE

Reputation: 500337

It's a long-standing bug in g++: http://gcc.gnu.org/bugzilla/show_bug.cgi?id=12255

The underlying issue is that G++ just ignores exception-specifications on non-function declarations. I think this choice originated in the uncertainty about whether or not the exeception-specification would become part of a function type rather than remain associated with the declaration.

It wouldn't surprise me if VS was similar in this regard.

Upvotes: 1

Mankarse
Mankarse

Reputation: 40603

This looks like a bug in GCC and VS2010. Clang won't compile it, and it should not compile according to [except.spec]/5:

... A similar restriction applies to assignment to and initialization of pointers to functions, pointers to member functions, and references to functions: the target entity shall allow at least the exceptions allowed by the source value in the assignment or initialization.

The standard also includes the following example:

class A { /*...*/ };
void (*pf1)(); // no exception specification
void (*pf2)() throw(A);
void f() {
    pf1 = pf2; // OK: pf1 is less restrictive
    pf2 = pf1; // error: pf2 is more restrictive
}

Upvotes: 1

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