[QPID-3344] Comparisons of const DataAddr objects are incorrect

• Type: Bug
• Status: Closed
• Priority: Major
• Resolution: Fixed
• Affects Version/s: 0.10
• Fix Version/s: 0.13
• Component/s: QMF

Environment

Fedora 15, not that it matters.

• Assignee: Ted Ross
• Reporter: Zane Bitter
• Created: 07/Jul/11 13:39
• Updated: 29/Jul/13 18:53
• Resolved: 12/Jul/11 16:12

Description

The following program results in incorrect output:

test.cpp

// g++ test.cpp -o test -lqmf2

#include <qmf/DataAddr.h>
#include <iostream>

int main(void)
{
    qmf::DataAddr foo("foo", "blarg", 1);
    const qmf::DataAddr bar("bar", "wibble", 2);
    

    // prints "false"
    std::cout << "foo == bar: " << (foo == bar ? "true" : "false") << "\n";

    // prints "true" (Doh!)
    std::cout << "bar == foo: " << (bar == foo ? "true" : "false") << "\n";

    return 0;
}

Anywhere where two DataAddr objects are compared and the first is a const reference will give a bogus result. (Specifically, both operands are converted to bool before being compared.) The reason is that DataAddr::operator==() is not declared const, so it will not be used to compare const references, and that C++ is pure, unadulterated evil.

Not that qmf::Data::getAddr() returns a const qmf::DataAddr&, so this is likely to be a common problem. Some other APIs, such as qmf::AgentEvent::getDataAddr() return non-const references, which would be unaffected (unless they become const at some point in the call chain).

A patch will follow presently.