[YBA] kernel compile errors with GCC >= 4.6

[Jonathan Ben Avraham]

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.

  - 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) 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
>
> 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.
>
>

-- 
  EE 77 7F 30 4A 64 2E C5  83 5F E7 49 A6 82 29 BA    ~. .~   Tk Open Systems
=}------------------------------------------------ooO--U--Ooo------------{=
      - yba at tkos.co.il - tel: +972.2.679.5364, http://www.tkos.co.il -