Why is clang not used more? [closed]

问题:

I've done a fair amount of programming in C/C++ before, but nowadays it only accounts for a small percentage of the programming I do (scripting languages are much better suited for a lot of the work I do). I worked on some C programming projects the last few days and was surprised how many little syntactical details I kept forgetting. What's worse is that cc/gcc typically had cryptic or non-informative error messages about these issues (sorry I can't remember any specific examples).

I learned about the clang compiler not too long ago and decided to try that. The error messages were much clearer and helped me identify and fix the problems in my syntax. My question is why this tool is not used/mentioned more than it is? Is it that it is so new compared to the usual suspects (cc/gcc), or is it that it doesn't support features that they support, or is it just harder to obtain? I have a hard time believing that last one, since it was installed with the dev tools on my iMac and required a single command (sudo apt-get install clang) to install on my Ubuntu box.

回答1:

My question is why this tool is not used/mentioned more than it is?

It's probably because of history, and because how we humans generally behave.

Traditionally gcc has been the only real (free) compiler that can be practically used to compile C programs on atleast all the free *nix clones out there. It's what virtually all the base system and kernel of linux, *BSD, now probably OSX, and others are compiled with.

While flaws are here and there, basically this means: gcc works. And if it isn't broken, don't fix it. Out of this, you now have a huge user base, it's easy to get help with gcc, there's a lot of people that have used gcc, that are working on gcc itself etc.

Generally, if you want to switch a huge community from something they're used to, to something else, that "something else" have to be *significantly" better. Just "better" is often not reason enough. I think you can find examples of this in many areas of society.

clang is newer, some people will just be suspicious if it's up to the task, if it has bugs, if it produces slower code etc. - it seems to be in the human nature to be suspicious - new things are scary. Many don't even know about clang, many don't care because they're happy with gcc.

Though, if you rather want to use clang, go for it - error messages are indeed "better" and easier to understand vs gcc.

回答2:

The clang front end is relatively new. For example, the 2.8 release in October 2010 marks the completion of the C++ 98/03 support.

It seems likely that with increasing maturity, there will be an increasing adoption. For example, there is ongoing work on making the FreeBSD OS (and other BSD OS's) build with clang, eliminating a dependence on GCC/G++.

Apple are pushing the LLVM/clang combination. It seems likely that they will cease to support their old GCC toolchain branch (based on 4.2) and come to depend solely on clang tools for OSX/iOS development.

Clang is also seeing increasing adoption in custom compilers for C-like languages (e.g. shader language compilers for OpenCL)

回答3:

LLVM has been around for a while, but — at least in my neck of the woods — it has only risen to prominence very recently, possibly due to the fact that Apple has been pushing heavily of late to replace gcc with Clang in their own tool-chain.

Also, I believe it's C++ support has only recently become production-grade. EDIT: It appears that it isn't even that yet. (See comments below.)

Another factor might be that LLVM is largely backed by a single vendor, towards which non-Apple developers have an innate mistrust.

回答4:

My question is why this tool is not used/mentioned more than it is? Is it that it is so new compared to the usual suspects…

This is exactly the reason. It is still new and core functionality is still being actively developed. Remember that existing projects may be making use of compiler-specific features – or using libraries which do – and developers are, in any case, loath to change working tools for experimental ones that may have unexpected bugs or unknown performance/size/etc. tradeoffs, even when the new tools are increasingly getting better every day.

回答5:

As a student programmer I find it a total godsend mainly due to it's helpful and understandable error messages. I use it mainly for programming in C, though I am beginning to branch out into C++ also using Clang.

As to why is it not mentioned more, I suspect it is since GCC has been established for so long, for most users it is THE compiler. GCC for me works fine except for it's extremely cryptic error messages which as a student does throw me off quite a bit.

Overall I do highly recommend Clang for use by both students and developers. Since it is now the official compiler for Apple and Xcode, I suspect it's use and name recognition will quickly pickup. FreeBSD seems to have also adopted it as their main compiler though I suspect that will have less impact on it's popularity than it's adoption by Apple.

Addendum: Due to the competition from Clang, the clarity of the error messages in GCC 4.8 and 4.9 has shown a significant improvement; though I still find Clang a little more lucid, the gap however has narrowed significantly.

回答6:

Today, clang is replacing gcc in most places. i.e., most *NIX-like operating system and Linux distributions. Some examples oare FreeBSD,Minix and mac(a bit obvious) clang that switched clang as default compiler. Some of my friends too,when I showed them.

This IMHO, looks like some peoples had problems with it,probably in older versions. But with clang version 3.0, I don't have any of this problems. As I metioned before, I'm using it really in all my new projects. Almost my default compiler, sometimes I do make C=gcc just to seen how difference to clang error/warning. And clang win ever. With better explanations and make a great effort to optimization. It include suggestions for use extensions(some are gcc inerhid) of the compiler to a best perfomance in the code generation.

I had written a trivial function that print an error message. But I would to exit from program after printed the error message on standard output. So,I make a simple modification,put an exit(1) as last statement in the function. As the following:

void error(const char *fmt, ...)
{
  va_list ap;
  va_start(ap, fmt);
  fprintf(stderr, "error: ");
  vfprintf(stderr, fmt, ap);
  va_end(ap);
  exit(1);
}

And so the clang show

warning: function 'error' could be declared with attribute 'noreturn' [-Wmissing-noreturn]`

(gcc doesn't produce it even not with -Wall -Wextra -Wunreachable-code -O3 flags)

I say "that seems like nice. But what is 'nonreturn' attribute? I'd never listen or read about this. I jump to google and search for clang could be declared with attribute 'noreturn' (oh,yeah,I could just written clang nonreturn attribute,but forget it) and I found this link with a good explanation of what it this attribute and the possible gain of perfomance that I could get.

So I run to add this attribute to my function prototype(of course,if it is the gcc or clang compiler; macros will do the trick-detection). Oh yeah,to me,any small gain of perfomance(of course,without making the code unreadable) it a win.

And don't ends here,some year ago,I make return in a function where the proviously is a switch as default handling defined(as in the error() function here). But even so, gcc clains about function without return-value(I'm sorry,I don't recall to exactly error/warning message) how it possible? there is no more statements after switch,if no case match,default value is executed and don't really matter the below statements,if any. But clang think different,like me,and give a warning about this declaration,helping me make better code.

And for this kind of very small thing, I'm loving the clang. (Note: I'm sorry for my bad english. English isn't my native language speaker, but despite it I'm trying express me here)