Build and manage large-scale C++ on Windows

DLLs versus shared objects

Build a business case: developing custom apps

As a result, once we identify the libraries we want to be DLLs and static we can identify the point in the dependency graph when the static library is first used by a DLL. We can add the "exports" of the static library to the DLL's exports list by using the /EXPORT option when linking the DLL. Any other users of that static library can now use it via this DLL to avoid duplicate definitions in the configuration.

What to do when it goes wrong

In a large project there will be of course many areas of responsibility producing many different deliverables. Often, such deliverables are provided in both static and dynamic configurations so those that want to link statically can and those who want the dynamic version are equally facilitated. Of course there's always the day when you need to link with one essential component, which is only available as a DLL and worse, it uses some other component in mode dynamic. Of course, this other component is the very same other component that everything else in your build uses in mode static and it's not necessarily easy to change that.

A consequence of the name decoration caused by exporting a symbol in Windows is that the binary name of a symbol coming from a DLL will be different that the name of the same symbol in a static library. OK, no big deal, one component uses the DLL version and the rest of the build configuration uses the static version. This should work, provided there is no data of static duration in the picture for the reasons we've already seen.

So what if there is some static data, what can be done to initialize it? Well if the data is initialized by a C function this isn't that hard. We can add code to our application to call LoadLibrary with the name of the DLL containing the static data. As the DLL is already loaded into the process we'll get a handle to this already loaded DLL. We then call GetProcAddress using this handle and the name of our function, casting the resulting function pointer appropriately and all is good again.

It's not always so easy though, as sometimes people will use constructors to initialize static data. It is possible to call a constructor in a DLL transitive dependency. It involves allocating memory with malloc, writing assembler to prepare the stack frame manually and calling the constructor as if it was a C function. This is unlikely to win awards for portable code though.

Navigate the differences

There are complexities specific to Windows DLLs especially when used with static libraries that contain data. As a consequence managing a large-scale project on Windows brings some additional considerations which should be thought about if supporting Windows in addition to Unix platforms is an issue. Even if the eventual product isn't cross platform, this issues can cause headaches if development and testing is supported on Windows, because some developers prefer tools on that platform.

In general, though, even with the additional complexity there's always a way to navigate the differences in the dynamic-linking model and I've yet to see a case of "we cant get that to run on Windows" that wasn't solvable.®

Boost IT visibility and business value

More from The Register

next story
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
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
Google shows off new Chrome OS look
Athena springs full-grown from Chromium project's head
prev story


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.
The Essential Guide to IT Transformation
ServiceNow discusses three IT transformations that can help CIO's automate IT services to transform IT and the enterprise.
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.
How modern custom applications can spur business growth
Learn how to create, deploy and manage custom applications without consuming or expanding the need for scarce, expensive IT resources.
Build a business case: developing custom apps
Learn how to maximize the value of custom applications by accelerating and simplifying their development.