GCC and LLVM - What's in a licence? (ITPro)

[Posted December 17, 2010 by corbet]

Here's an ITPro article (obnoxiously split into six parts) comparing GCC and LLVM from a licensing point of view. "In other words GCC is constructed in such a way that those who wish to provide extensions with licences that are incompatible with the GPL and copyleft are persuaded to contribute the software back to the community in the shape of the GPL - and this has been beneficial to the community - in that it has opened up architectures and languages that might not otherwise have been available to other users of GCC."

GCC and LLVM - What's in a licence? (ITPro)

Posted Dec 17, 2010 16:07 UTC (Fri) by TeDiouS (guest, #67602) [Link]

It was a nice read. I knew a majority of it already, but it was nice.

GCC and LLVM - What's in a licence? (ITPro)

Posted Dec 17, 2010 17:49 UTC (Fri) by JoeBuck (subscriber, #2330) [Link]

It's a well-written article (and it quotes me accurately without misunderstanding my point, which is always a relief), and it does a better job describing the costs and benefits of GPL vs BSD than most.

However, it's out of date. The quote of mine that is extensively discussed is three years old (November 2007), and was attempting to explain why it had been difficult to get RMS to agree to gcc plugins. But we found a way to resolve that issue while still preserving an incentive to make keep the GCC extensions free, and GCC now has a plugin architecture. Yes, it still isn't nearly as modular as LLVM, but it's been shifting in that direction. It would have been useful for the article to discuss plugins and what they can and can't achieve compared to building on LLVM.

My view is that the non-modularity of GCC, at one time, helped to motivate contributions (see the article for specific examples), but that's no longer the case. Today, anyone who wants to build proprietary software that requires good compiler technology have a range of choices: LLVM for free, or the EDG front end for not very much.

GCC and LLVM - What's in a licence? (ITPro)

Posted Dec 17, 2010 18:31 UTC (Fri) by egoforth (subscriber, #2351) [Link]

There will always be arguments over which licence is more useful and/or 'free'. BSD-style licences offer greater short term freedoms, but can be diverted for proprietary ends. The GPL guarantees continued and extensible freedom for the code, but should architectural considerations be subsumed by the greater need for freedom of the code?

Much more clueful article than I've come to expect from most industry rags.

GCC and LLVM - What's in a licence? (ITPro)

Posted Dec 20, 2010 15:17 UTC (Mon) by jsdyson (guest, #71944) [Link]

One of the most important attributes of the larger BSD (or GPL) licensed projects (those with sufficient critical mass) is that future contributions back to the original codebase are encouraged by the long term support costs/issues. The free software projects provide an ongoing support mechanism that is commercially fairly costly. So, forking a project like LLVM for 'selfish gains' can be more costly than if the work is fed back to the original project, even if very freely licensed like BSDL. The costs of long term commercial support of a highly forked project equivalent to a non-GPL GCC, would likely outweigh any benefit. A 'wise' business person will most likely feed back the changes. The same is true for LLVM. On smaller projects, with less of a central critical mass, this argument is not quite so convincing.

So, BSDL software does not have to depend upon altruism, because feeding back changes to the original development can quite often have a selfish benefit. In the case of (at least) GPLv2, there is no legal requirement that I know of that the changes be fed back to the mainline tree, but that those who receive binaries also have bona fide access to the source. On the other hand, both BSDL and GPL software have the 'selfish' support cost motive to feed back substantial improvements.