What’s new in ElectricAccelerator 6.2?

We released ElectricAccelerator 6.2 a couples weeks ago, our 25th feature release. 6.2 was a quick interim release primarily intended to address a couple long-standing stability issues, but we managed to squeeze in some really interesting feature enhancements as well. Here’s what’s new:

Rules with multiple outputs? Yeah, we can do that.

Every now and then, makefile authors need to write a single makefile rule that produces more than one output file, to accomodate tools that don’t fit gmake’s rigid one-command-one-output model. The classic example is bison, which produces both a C file and a header file from a single invocation of the tool.

Unfortunately in regular gmake the only way to write a rule with multiple outputs is to use a pattern rule. That’s great — if your needs happens to dovetail with the caveats and limitations of pattern rules (chiefly, that the output files share a common base name). If not, the answer has been basically that you’re out of luck. There are a variety of kludges that approximate the behavior, but despite numerous requests over the last decade (1, 2, 3, 4, 5, 6, 7, 8) and at least one patch implementing the feature, GNU make (as of 3.82) still has no way to create an explicit rule that produces multiple outputs.

When it comes to enhancements to the fundamental operation of GNU make, we’ve historically let the GNU make team take the lead, rather than risk introducing potentially incompatible changes. But after so many years it seems clear that this feature is not going to show up in GNU make — so we decided to forge ahead on our own. Enter #pragma multi:

GNU make interprets this construct as two independent rules, one for foo and one for bar, which happen to each create both files. Thanks to the #pragma multi designation, Electric Make will interpret this as a single rule which produces both foo and bar. Using a #pragma to flag the rule is perfect, because it sidesteps any questions about syntax changes. And since #pragma starts with a #, GNU make will treat it as a comment, so this makefile will still be usable with GNU make — you’ll just get correct behavior and better performance with Electric Make.

New platforms and a faster installer

Accelerator 6.2 adds support for Linux kernels up to 3.5.x, which means that Accelerator now supports the following platforms:

• Ubuntu 11.10
• Ubuntu 12.04
• SUSE Linux Enterprise Server 11 SP2

In addition, Accelerator 6.2 is expected to work correctly on both Ubuntu 12.10 and Windows 8, although we cannot officially claim support for those platforms since they were themselves not finalized at the time Accelerator 6.2 was released. This release also incorporates enhancements to the Linux installer which make the installation process about 25% faster compared to previous releases.

A complete list of platforms supported by ElectricAccelerator 6.2 can be found in the Electric Cloud Knowledge Base.

Key robustness improvements

Raise your hand if you’ve ever seen this error on your Linux Accelerator agent hosts:

unable to unmount EFS at “/some/path”: EBUSY

That error shows up sometimes when your build starts background processes — kind of a distributed build anti-pattern itself, but unfortunately it’s not always something you can control thanks to some third-party toolchains. Or rather, that error used to show up sometimes, because in Accelerator 6.2 we’ve bulletproofed the system against such rogue background processes, so that error is a thing of the past (nota bene: this enhancement is not available on Solaris).

In addition, we bulletproofed the system against external processes (any process running on an agent host which is not part of your build) accessing the EFS. In certain rare circumstances, such accesses could lead to agent host instability.

What’s next?

With 6.2 out the door we’ve finally got bandwidth to work on 7.0, which will focus on some very exciting performance improvements, especially for incremental builds. It’s a little bit too early to share any of the preliminary results we’re seeing, but rest assured — if you thought Accelerator was fast before, well… you ain’t seen nothing yet! Stay tuned for more information.

ElectricAccelerator 6.2 is available immediately. If you are already an Accelerator user, contact support@electric-cloud.com to upgrade. If you are not currently a user, you can download a free evaluation version of ElectricAccelerator Developer Edition, or contact sales@electric-cloud.com.