Are there subsets of C that avoid compiler bugs?

http://blog.regehr.org/archives/539

by gnosis • 15 years ago

38 21 15 years ago

blog.regehr.org

evangineer4• 15 years ago

If you use the Clight subset with the CompCert C Compiler, the answer is yes:

http://compcert.inria.fr/compcert-C.html#subset

In any other case, the answer is almost certainly no. Most commonly used C compilers are sufficiently large and complicated that the chances of avoiding a compiler bug with a sufficiently large codebase is close to zero.

mansr2• 15 years ago

Compcert is not without bugs either. The very blog this post references talks about some.

evangineer4• 15 years ago

Thanks for the heads up, I hadn't seen anything in the article about CompCert, but on doing a search I found there are quite a few mentions of it on other articles on the blog:

http://blog.regehr.org/?s=compcert&searchsubmit=Search

evangineer4• 15 years ago

Cyclone was an attempt at creating a safe dialect for C, it might be of some interest to people who have read the article:

http://cyclone.thelanguage.org:8181/

SamReidHughes• 15 years ago

That's not the kind of safety we're talking about.

evangineer4• 15 years ago

I realised that, as Pascal might put it Cyclone is a C like language designed to ensure that programs are correct. I saw it as a related form of safety others might be interested in.

I already posted on Clight & CompCert which is much more salient in terms of ensuring compiler correctness and a safe subset that falls within the scope of the verified compiler's correctness.

jimbobimbo• 15 years ago

Microsoft's take on making C and C++ safer - SAL: http://blogs.msdn.com/b/michael_howard/archive/2006/05/19/60...

profquail• 15 years ago

They also created VCC (Verifying C Compiler), which uses their Z3 theorem prover to check for bugs (especially concurrency bugs, which can be really tough to find).

http://vcc.codeplex.com/

pascal_cuoq• 15 years ago

SAL and VCC are for making C programs correct. This is related but not the same thing as making the C compiler correct. These source-level tools assume that the compiler translates the programs correctly.

keithnoizu• 15 years ago

Hopefully we are self hosting at this point and smart enough to apply SAL and VCC to our compiler itself.

tedunangst• 15 years ago

So far all the comments have focused on this issue as a C language specific problem, as if some other language won't be affected, but it's really universal to optimizers. Optimization is subtle and hard. JIT engines get burned, too.

BruceForth• 15 years ago

I wonder if there are compilers that don't compile an empty file correctly.

mansr2• 15 years ago

There are.

chrisjsmith4• 15 years ago

Assembly is the only language that will eliminate compiler bugs...

Peaker2• 15 years ago

That and certified/proven compilers.

chrisjsmith4• 15 years ago

I used to work for a large defence company. They paid for "certified" ADA compilers for PPC architecture. They had as many (if not more) bugs. Not only that, they built their stuff on FPGAs which had even buggier compilers than the compilers for the software.

Certified compilers are protected only by maintenance agreements.

CountHackulus• 15 years ago

They'll only eliminate compiler bugs because there is no compiler. Assembler, linker, and loader bugs will still be there.

Are there subsets of C that avoid compiler bugs?

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