Feeds

Binary interfaces in component development

A template class with static data - how can that possibly go wrong?

Boost IT visibility and business value

Part 2 In the first part of this series we looked at how problems emerge when we make the transformation from source code to binary code, and we saw that even when the code is correct errors can be introduced by using dynamic libraries instead of a monolithic binary.

With some simple examples, we’re starting to see problems, using a logically correct C++ program for which we cannot construct a physical representation using dynamic libraries because of platform constraints.

In software security, the industry experts speak of security exposures that occur in the interactions between systems. I think we’re now seeing a similar issue with the interaction of the abstract C++ system and the physical portable executable format system; but instead of a security problem, we get bugs.

Our example comes from real life code, and a large development team that has lived with consequent problems in its Windows environment for a long time, which have cost a lot of money. The issue comes from the interaction of two C++ language features that behave unexpectedly when combined with dynamic linking. We’ll see how on Windows that code packaged in dynamic libraries doesn’t behave in accordance with the C++ language, and we’ll see how to use tools to investigate and resolve the problem. The code we’ll use to expose this insidious problem is shown in the following generic implementation of the Singleton pattern. As we’ll see, this code works fine provided it is not used with dynamic libraries:

// GenericSingleton.hpp
template <typename T>
class GenericSingleton
{
public:
   T &getInstance();

private:
   static T m_instance;
};

template <typename T>
T & GenericSingleton<T>::getInstance()
{
    return m_instance;
}

template <typename T>
T GenericSingleton<T>::m_instance; 

There’s a template class with all of its definitions in the header file. This organisation of a class template is common, perhaps because placing the template definitions in the header file avoids lots of annoying linker warnings. However, as we’ll see, this practice leads to problems once the transition is made from a small monolithic binary program to a modular software system composed of interacting dynamic libraries.

Firstly, why is this code problematic in conjunction with dynamic libraries? There are issues here on Windows and on Linux, but the manifestations of the problems are different.

Boost IT visibility and business value

More from The Register

next story
NO MORE ALL CAPS and other pleasures of Visual Studio 14
Unpicking a packed preview that breaks down ASP.NET
KDE releases ice-cream coloured Plasma 5 just in time for summer
Melty but refreshing - popular rival to Mint's Cinnamon's still a work in progress
Leaked Windows Phone 8.1 Update specs tease details of Nokia's next mobes
New screen sizes, dual SIMs, voice over LTE, and more
Another day, another Firefox: Version 31 is upon us ALREADY
Web devs, Mozilla really wants you to like this one
Put down that Oracle database patch: It could cost $23,000 per CPU
On-by-default INMEMORY tech a boon for developers ... as long as they can afford it
Secure microkernel that uses maths to be 'bug free' goes open source
Hacker-repelling, drone-protecting code will soon be yours to tweak as you see fit
Mozilla keeps its Beard, hopes anti-gay marriage troubles are now over
Plenty on new CEO's todo list – starting with Firefox's slipping grasp
prev story

Whitepapers

Implementing global e-invoicing with guaranteed legal certainty
Explaining the role local tax compliance plays in successful supply chain management and e-business and how leading global brands are addressing this.
Consolidation: The Foundation for IT Business Transformation
In this whitepaper learn how effective consolidation of IT and business resources can enable multiple, meaningful business benefits.
Backing up Big Data
Solving backup challenges and “protect everything from everywhere,” as we move into the era of big data management and the adoption of BYOD.
Boost IT visibility and business value
How building a great service catalog relieves pressure points and demonstrates the value of IT service management.
Why and how to choose the right cloud vendor
The benefits of cloud-based storage in your processes. Eliminate onsite, disk-based backup and archiving in favor of cloud-based data protection.