[YBA] kernel compile errors with GCC >= 4.6

[Orna Agmon Ben-Yehuda]

On Thu, Apr 5, 2012 at 11:07 AM, Jonathan Ben Avraham <yba at tkos.co.il>wrote:

> Hi Nadav,
> Your point is well taken.
>
> -Werror has been in GCC for a long time (4.2.2 at least).
>
> I don't know how long it has been a default flag in the kernel, but I
> understand why it is. You really do want the compilation to stop and to
> take a look at what is going on.
>
> For other projects I think that the Makefile or build system that is
> distributed with the project should only use -Werror after checking that
> the GCC version is the same as the version used by the developers for the
> release.
>

Same or earlier:
1. I expect compilers to identify more problems (some of which are annoying
false positives) as they develop.
2. Who says all developers use the same compiler version?


>  - yba
>
>
> On Thu, 5 Apr 2012, Nadav Har'El wrote:
>
>  Date: Thu, 5 Apr 2012 10:57:19 +0300
>> From: Nadav Har'El <nyh at math.technion.ac.il>
>> To: Oleg Goldshmidt <pub at goldshmidt.org>
>> Cc: Jonathan Ben Avraham <yba at tkos.co.il>, ILUG <linux-il at cs.huji.ac.il>
>> Subject: Re: [YBA] kernel compile errors with GCC >= 4.6
>>
>>
>> On Wed, Apr 04, 2012, Oleg Goldshmidt wrote about "Re: [YBA] kernel
>> compile errors with GCC >= 4.6":
>>
>>> On Wed, Apr 4, 2012 at 10:03 AM, Jonathan Ben Avraham <yba at tkos.co.il
>>> >wrote:
>>>
>>>  Dear linux-il colleagues,
>>>> GCC 4.6 introduced many new warnings that cause -Werror to stop the
>>>> compilation for some platforms, such as powerpc, in various files.
>>>>
>>>
>>> Oh, I didn't even know they finally introduced -Werror... Good.
>>>
>>
>> Why is this good?
>>
>> In the (very) old days, there was a clear separation: The compiler
>> gave you *errors*, and a separate program, call "lint",
>> (http://en.wikipedia.org/wiki/**Lint_%28software%29<http://en.wikipedia.org/wiki/Lint_%28software%29>)
>> was used to find
>> various risky code, possible bugs, unused variables, and so on, and
>> warn on them.
>>
>> I *don't* like the fact that modern compilers decide to complain on
>> issues of questionable style, such having a variable which is never
>> used, using "=" (deliberately, not ==) in an "if"'s expression, and so
>> on. I like even less the trend to use something like "-Werror" to *abort*,
>> not just warn, on these cases.
>>
>> After our last Hspell release, I started receiving complaints from
>> various people who used slightly different compilers than I did, so got
>> different *warnings* that I didn't get. This was very annoying, because
>> although I could (and did) fix those warnings, most of them did not have
>> any merit, and the only reason why I made many of these changes was to
>> "appease" the compilers. In one example, the compiler wrongly deduced
>> that a
>> variable could be used before being set, which was false (I can explain
>> why,
>> but the details aren't important here). In another example, a header file
>> defined a few static arrays, and not all of them were needed in each
>> including file - and the compiler complained about the
>> defined-but-not-used
>> static arrays.
>>
>> I think all of this is bad. I agree that it's useful to have a tool
>> (lint, gcc -Wall, or whatever), for the *developer* to find possible
>> problems. But the developer shouldn't *have* to change the code to
>> appease this tool, if he doesn't want to. The compiler that a *user*
>> of this code uses should definitely not attempt to look for such
>> "possible" problems, and most definitely should not abort the
>> compilation if it finds some. The contract between the programmer and
>> the user is that the programmer writes the code as carefully as he can -
>> and the user tries the best he can to compile it, NOT find reasons for
>> the compilation to fail. See also http://en.wikipedia.org/wiki/**
>> Postel%27s_law <http://en.wikipedia.org/wiki/Postel%27s_law>
>>
>> If -Werror is used in a big-enough project, there is a very high
>> probability that compilation will always fail when a new version of the
>> compiler is first tried. I fail to see why this is a good thing.
>>
>>
>>
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-- 
Orna Agmon Ben-Yehuda.
http://ladypine.org
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