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GCC Compiler Finally Supplanted by PCC?
Sunnz writes "The leaner, lighter, faster, and most importantly, BSD Licensed, Compiler PCC has been imported into OpenBSD's CVS and NetBSD's pkgsrc. The compiler is based on the original Portable C Compiler by S. C. Johnson, written in the late 70's. Even though much of the compiler has been rewritten, some of the basics still remain. It is currently not bug-free, but it compiles on x86 platform, and work is being done on it to take on GCC's job."
I notice that TFS doesn't say that anyone is actually able to compile anything (other than PCC) with it. The BSD folks would love to have a BSD-licensed drop-in replacement for GCC; but it doesn't sound like this is it. Not yet at least.
./build.sh or whatever).
Wake me up when you're able to use PCC instead of GCC to do a 'make world' (or
Kind of depends on who you ask, doesn't it?
OK, so it compiles C on x86. What do I use when I want to compile objective C on my microwave?
Someone relicense it under the GPL!
I really don't see any point in implementing a new C compiler under the BSD lisence. There's no reason to duplicate effort: it's not like the compiled binaries would be under the GPL. And any GPL libraries you link to, you wouldn't need to distribute (thus avoiding the GPL). So, really, there's no point in duplicating effort on a BSD lisenced compiler. Correct me if I'm wrong.
Seriously. Let's duplicate the wheel twice: once for GPL, once for BSD, and then bicker amongst ourselves. Stuff like this stands in the way of actual progress being made. Neither side is right, I don't have a solution, but this is just dumb.
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call me when pcc does something useful, like, say, working.
pcc will take YEARS to get the functionality and optimizations that gcc has. Even if it compiles slowly and sometimes generates dumb code.
Either way, they'd much, much better off if they imported LLVM and redirected their compiler brain power to clang.
PCC is interesting, but it's based on technology from the 70's, doesn't support a lot of interesting architectures, and has no optimizer to speak of.
If you're interested in advanced compiler technology, check out LLVM, which is an ground up redesign of an optimizer and retargettable code generator. LLVM supports interprocedural cross-file optimizations, can be used for jit compilation (or not, at your choice) and has many other capabilities. The LLVM optimizer/code generator can already beat the performance of GCC compiled code in many cases, sometimes substantially.
For front-ends, LLVM supports two major ones for C family of languages: 1) llvm-gcc, which uses the GCC front-end to compile C/C++/ObjC code. This gives LLVM full compatibility with a broad range of crazy GNU extensions as well as full support for C++ and ObjC. 2) clang, which is a ground-up rewrite of a C/ObjC frontend (C++ will come later) that provides many advantages over GCC, including dramatically faster compilation and better warning/error information.
While LLVM is technologically ahead of both PCC and GCC, the biggest thing it has going is both size of community and the commercial contributors that are sponsoring work on the project.
-Chris
GCC's intermediate formats GIMPLE and GENERIC are based on a research compiler, not a deliberate perversion. There's no technical steps to stop reuse, and indeed it has been done - Sun distribute the GCC 4.0.4 front-end altered to use their own SPARC code generator as a back-end.
Well that explains a lot. And here I was thinking that all modern compilers were designed correctly with a front-end and back-end. So much for academics.
Actually, the post you're replying to is total bollocks. GCC has had a clear divide between front and back end (not to mention a source-language independent middle layer for performing optimizations) since I first looked at it in about 1996. Each layer is hideously complex, but they are all there.
- Must compile C code (GCC does this).
- Must support all of the platforms OpenBSD targets (GCC has a habit of dropping support for various platforms).
- Must be easy to add new backends for new architectures (GCC makes this really hard).
- Must be easy to audit for security (GCC is a tangled mess).
Maybe a few I've missed. GCC is like Linux; it's a fairly good solution for a lot of problems, but it's rarely the best solution for any given problem. PCC is a better fit for the needs of the OpenBSD base system.I am TheRaven on Soylent News
The biggest reason for the new compiler (despite the jackass article submitter's position) is that GCC does *NOT* support every architecture. GCC drops architectures frequently as the core contributors lose interest, which hurts OSes like NetBSD that try to support more than the mainstream architectures. NetBSD relies on a combination of GCC 2, 3, and 4 to compile the OS on all of the architectures it supports.
The idea with PCC is not that it will be BSD licensed (nobody really gives a fuck what license the compiler is under), but that it will be supported directly by the BSD community, including the NetBSD hackers who have their bazillion architectures to support.
First: PCC has not YET supplanted GCC. The BSDs are hoping it will in the future.
Second: The biggest attraction of PCC is NOT the license. The article submitter who stated otherwise is a jackass.
Third: There are techical reasons why GCC is actaully unusable by some BSDs, such as NetBSD, which aims to support many architectures that GCC has dropped. NetBSD uses a combination of GCC 2, 3, and 4 to compile all of its different architectures. The NetBSD developers would rather have a single compiler that handles them all. Obviously PCC is nowhere near that level yet, of course.
Fourth: GCC politics are a pain in the ass for many BSD developers who just want to submit patches to a compiler without the overhead of GNU's policies and GCC's management.
Fifth: GCC produces crappy code more often than anyone would like. GCC bugs are far from unheard of, performance of generated code is often unpredictable between releases, and in many less commonly used architectures or sources GCC will produce incorrect code. Yes, these cases are very rare, but the BSD folks have hit the problem often enough for it to be a concern. PCC, being simpler and less bloated with cruft from multiple rewrites of the internals will hopefully produce correct and predictable code more often than GCC.
Sixth: PCC actually works today. It can compile most of the NetBSD userspace, as I recall, and the kernel will be ready to roll soon after some inline assembler problems are fixed. This isn't some theoretical hacky project - it works right now. It's not ready to replace GCC just yet, by any means, but it's a lot more than some Slashdotters seem to think it is.
You couldn't have gotten that statement any MORE WRONG if you had tried.
GCC's "production quality" is an on-again, off-again thing. Through most of v3.x it had too many bugs to count, and was inherently unreliable. It couldn't even compile ITSELF with the most basic optimizations or the resulting binary would generate incorrect code. Up until v4 it also misaligned stack variable. It had, and still has, MANY bugs. That GCC successfully compiles code at all is almost entirely due to it being so popular that everyone knows it, and works around its bugs without even thinking about it.
It has never had GOOD support for any other platforms than x86. Remember the RedHat GCC2.96 fiasco? They forked it because they needed it to support more platforms than it currently did. And even through v3.x the non-x86 ports of GCC had even more bugs than on x86, commonly falling apart if you attempt to use any optimizations. Now, they're DROPPING support for those platform entirely, which is a big problem for developers of operating systems for those platforms.
"Improved" is pretty vague. HURD has probably been "improved" for every minute of it's existence as well... Meanwhile the far younger ICC (Intel's compiler) beats the pants off of GCC without even trying.
What's more, GCC's "improvements" come at great cost. If you're a full-time developer, for the final release you want optimized code, but while developing, you want to compile and be able to test code frequently, and so as quickly as humanly possible. GCCv3+, even with all optimizations disabled, takes far, far longer to compile binaries than even older versions of GCC, and as it says, something like 10X slower than PCC.
The license issue is only incidental. These (and other) problems pushed them away from using GCC. Since they happen to be BSD developers, they'd prefer their work to be BSD licensed, and so it is.
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Think about it. Getting a new compiler into free UNIX and the open source community is going to be as hard as getting a new platform on the desktop to compete with Windows. And for similar reasons.
You're not going to supplant GCC until you get all the code that depends on GCC-specific features modified to be standard portable C. That's a barrier to entry as steep as Microsoft's application barrier to entry. Now it's not as bad as it was in the early '90s when GCC was sprouting new C extensions everywhere (like the ability to have declarations not at the start of blocks, or the ability to leave the second element out of the trinary conditional operator, or things like alloca), and a lot of those features have now become common and even standardized (and others, like the shortcut trinary, have been deprecated). But it's not as easy as just having a good compiler, or even a good language translating ecosystem like Tendra... the playing field is anything but level.