[YBA] kernel compile errors with GCC >= 4.6

[Shlomi Fish]

Hi all,

On Thu, 5 Apr 2012 12:47:10 +0300
geoffrey mendelson <geoffreymendelson at gmail.com> wrote:

> 
> On Apr 5, 2012, at 12:35 PM, Jonathan Ben Avraham wrote:
> >
> > I think that it would be best if kernels were released with the list  
> > of compiler types and versions under which they were tested before  
> > release. It is not useful to pretend that there is no necessary  
> > connection between particular GCC versions and particular kernel  
> > versions. The compiler is in fact a part of the running kernel.
> 
> 
> Around 2000, Intel went into the business of selling Linux compilers.  
> You could use them free (as in beer, not FOSS) for personal use.

Are you sure about it? I recall downloading a trial version of the Intel C++
Compiler and experimented with it for a while, and then the trial period ended
and I was no longer able to use it. The Wikipedia page does not appear to
mention the terms for using the compiler either:

http://en.wikipedia.org/wiki/Intel_C%2B%2B_Compiler

I suppose I can try it again.

One should note that it was discovered that ICC discriminates against
non-"Genuineintel" CPUs by choosing a non-optimised path for them, so it
cannot be reliably used for cross-CPU benchmarks. More information here:

http://en.wikipedia.org/wiki/Intel_C%2B%2B_Compiler#Criticism

> 
> Their C compiler had special code in it to detect that you were  
> compiling a Linux Kernel and it reproduced the bugs in GCC to match  
> it. :-)

Hmmm... I know the Linux version of ICC aimed for close to 100% GCC
compatibility, but I’m not sure if it treats (or treated) the kernel any
differently. If so, this reminds me of the SimCity story about Windows:

From http://www.joelonsoftware.com/articles/fog0000000054.html :

[QUOTE]
Windows 95? No problem. Nice new 32 bit API, but it still ran old 16 bit software perfectly. Microsoft obsessed about this, spending a big chunk of change testing every old program they could find with Windows 95. Jon Ross, who wrote the original version of SimCity for Windows 3.x, told me that he accidentally left a bug in SimCity where he read memory that he had just freed. Yep. It worked fine on Windows 3.x, because the memory never went anywhere. Here's the amazing part: On beta versions of Windows 95, SimCity wasn't working in testing. Microsoft tracked down the bug and added specific code to Windows 95 that looks for SimCity. If it finds SimCity running, it runs the memory allocator in a special mode that doesn't free memory right away. That's the kind of obsession with backward compatibility that made people willing to upgrade to Windows 95.
[/QUOTE]

These are the kind of workarounds that justify the maxim "Backwards
compatibility is compatibility done backwards.". ;-).

Regards,

	Shlomi Fish

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