[Bug 11800] building SES support fails w/ gcc-3.4.5

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http://bugzilla.kernel.org/show_bug.cgi?id=11800





------- Comment #7 from anonymous@xxxxxxxxxxxxxxxxxxxx  2008-10-27 10:48 -------
Reply-To: beej@xxxxxxxxxxxx

At 12:35 10/23/2008, James Bottomley wrote:
 >On Thu, 2008-10-23 at 12:14 -0400, Marc Bejarano wrote:
 >> At 17:17 10/22/2008, James Bottomley wrote:
 >>  >On Wed, 2008-10-22 at 13:30 -0700, Andrew Morton wrote:
 >>  >> OK, it's here:
 >>  >>
 >>  >>         buf = kmalloc(vpd_len, GFP_KERNEL);
 >>  >>
 >>  >> it's a gcc bug.
 >>  >>
 >>  >> Please see if you can find some way to make it go away - perhaps change
 >>  >> vpd_len's type to `int', things like that.
 >>  >>
 >>  >> Or use a different compiler version :(
 >>
 >> i'm not worried about compiling this.  i already did a compilation
 >> without it and i'll be fine without SES.  i just selected it on the
 >> off chance i'd find time to play with it.  i was just doing my duty
 >> of reporting this to save others the trouble.
 >>
 >>  >Could it be an optimisation issue?  The static oversize test relies on
 >>  >the compiler optimising away a leg that can never be reached if the size
 >>  >is under the max. If you do a make V=1 you'll see what optimisation
 >>  >flags the compiler is using ... if it's -O2 then yes, the compiler
 >>  >should be optimising stuff away and it's a clear compiler problem.  If
 >>  >it's anything else, we might have a mis setting of the optimisation
 >>  >level in the kernel build.
 >>
 >> looks to me like -Os:
 >
 >I think we have a winner: -Os is rather less well implemented in older
 >versions of gcc.  Could you retry with -O2?
 >
 >You do this by setting the config option
 >
 >CONFIG_CC_OPTIMIZE_FOR_SIZE

verified.

setting CONFIG_CC_OPTIMIZE_FOR_SIZE=n in .config does allow ses.c to 
be compiled by gcc 3.4.5 from the CentOS 4 gcc-3.4.5-2 RPM.

 >If we verify this to be the root cause, we
 >might consider making the default for that option N if gcc version is <
 >4.

marc


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