LLVM Coding Standards

[Daniel Gibson]

Am 12.04.2011 00:31, schrieb Spacen Jasset:
> On 11/04/2011 20:58, spir wrote:
>> [slightly OT]
>>
>> Hello,
>>
>> I'm reading (just for interest) the LLVM Coding Standards at
>> http://llvm.org/docs/CodingStandards.html. Find them very interesting
>> because their purposes are clearly explained. Below sample.
>>
>> Denis
>>
> 
> That seem all fairly sensible. It also reminds me of open source
> projects written in C, where GOTO is used, like so:
> 
> 
> HANDLE handle1 = open(...);
> 
> ...
> if (out_of_memory)
>     goto cleanup;
> 
> if (invalid_format)
>     goto cleanup;
> ...
> 
> cleanup:
>    if (handle1)
>       close(handle1);
>    if (handle2)
>     close(handle2);
> 
> 
> This code uses the dreaded goto statement, but I belive you can see that
> the author is trying to make the code more readable, or at least get rid
> of the nested indents/multiple cleanup problem you inevitably come
> across at some points in C code. It does tend to be more readable than
> the alternative, too.
> 

I agree. I've seen and used this in C code as well.
IMHO it is mostly a workaround for not having exceptions in C - the
cleanup-stuff would belong in catch{...} or finally{...} (or even
better, when scope-guards are available, in scope(exit){...} or
scope(failure){...}
And I agree that this is far more readable than using a plethora of bool
flags and ifs.

> I think that people like to follow rules, that is as soon as they have
> internalised them and made them their own. What this means is that they
> often then follow them to a fault, and you get deeply nested, but
> "structured" code, where instead you would be better of with more
> logically linear code as in the case of the early exit. Coding standards
> should probably just say: try and write readable code. Everyone knows
> what readable code looks like. It just not always quick or easy to make
> it that way.
> 
> 
> While I am on the subject, I've *always* thought major languages have
> poor loop constructs:
> 
> 
> (A)
> 
> for (;;)
> {
>     std::getline(is, line);
>     if (line.size() == 0)
>         break;
>     ...some things...
> }
> 
(...)
> 
> Instead you could just have:
> 
> loop
> {
>  ...
>  if (condition) exit;
>  ...
> }
> 
> instead of WHILE and DO. Whereby you *must* have an exit condition.
> 
> 
> But I suppose you need a FOR loop because the following may be error prone.
> 
> int x=0;
> loop
> {
> if x > 9 exit;
> ...
> x++;
> }

Yeah. And I guess while-loops also have their uses.
I think just loop like you're suggesting is not available because
for(;;) and while(1) achieve the same thing without too much additional
typing.

Cheers,
- Daniel