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Distributions looking at LLVMDistributions looking at LLVMPosted Mar 23, 2012 8:54 UTC (Fri) by khim (subscriber, #9252)In reply to: Distributions looking at LLVM by Yorick Parent article: Distributions looking at LLVM
We use GCC and are mainly happy with it, but do build with Clang from time to time, just to see if it catches something that GCC didn't - and it often does. This is biased selection. Both GCC and Clang have cases where one compiler produces garbage and another gives you nice and clean message, but if you if only run Clang when GCC produced garbage then you are missing cases where GCC gives clean messages and Clang blows up. Interestingly, Clang builds our code base slower than GCC. Again: YMMV. Often Clang is faster but in our codebase there are file which GCC compiles in 50seconds with full optimization while Clang needs 9 minutes - that's 10x slowdown (MSVC is two times worse then Clang). This is most likely because our compile times are dominated by a few very large (>100000 lines) machine-generated C files with very large functions, and apparently Clang doesn't handle this quite as well as GCC. LOL. Our case is similar, too. Clang and GCC produce code of similar speed and size in the end even if one needs 10x more time then the other.
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Distributions looking at LLVM Posted Mar 23, 2012 14:57 UTC (Fri) by Yorick (subscriber, #19241) [Link] This is biased selection. Both GCC and Clang have cases where one compiler produces garbage and another gives you nice and clean message, but if you if only run Clang when GCC produced garbage then you are missing cases where GCC gives clean messages and Clang blows up.Certainly — swap GCC and Clang, and my statement would have been equally valid. I'm happy that we have not just one but two free compilers of very high quality, that implement most of the same language extensions and even take the same command-line options. We do run both GCC and Clang with -Wall -Werror, by the way, forcing ourselves to fix even minor complaints from either compiler. This has proven very effective.
Distributions looking at LLVM Posted Mar 23, 2012 19:33 UTC (Fri) by oak (guest, #2786) [Link]
It's nice to hear that Clang has significantly improved!
I've used GCC v4.4 and Clang v1.1 / LLVM v2.7 in Debian stable to compile largish C programs and with these old versions GCC provides much superior detection of issues (while the errors Clang reports are more readable).
Which versions of GCC and Clang/LLVM you were using?
Btw. I would recommend adding quite a few extra warning options to GCC & Clang as -Wall misses quite a few things that can go wrong. For example: -Wextra -Wmissing-prototypes -Wstrict-prototypes -Wold-style-definition -Wcast-qual -Wbad-function-cast -Wpointer-arith -Wwrite-strings -Wformat-security -Wshadow.
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