Problem building kernel 4.0 with gcc5 Werror

[Paul Bolle]

On Sat, 2015-05-09 at 18:28 -0500, Victor Rodriguez wrote:
> I am trying to build the kernel 4.0 with gcc 5 . But I found the
> following problem :
> 
> builtin-report.c comparison of constant ‘-1’ with boolean expression
> is always false
> 
> THe problem is that gcc5 has new warnings:
> 
> A new command-line option -Wbool-compare has been added for the C and
> C++ compilers, which warns about boolean expressions compared with an
> integer value different from true/false.
> https://gcc.gnu.org/gcc-5/changes.html

I think the problem is actually that the code is broken. See commit
fefd2d9619de ("perf report: Fix branch stack mode cannot be set") in
linux-next which links to
http://lkml.kernel.org/r/1423967617-28879-1-git-send-email-hekuang@huawei.com . 
 
> I was checking the Makefile of tools/perf/ anda aprently they became
> every warning into an error. Werror

(tools/perf/Makefile.perf has this line
    # Define WERROR=0 to disable treating any warnings as errors.

Perhaps that might help you get past this build error. I don't know, I
never tried it. But the best thing here seems to use that patch. I guess
it should eventually show up in the v4.0.y-stable tree.)

> Now I wonder if someone is working on this changes so I can take their pathces.
> 
> Do you know any easy way that GCC use to avoid this kind of problems
> 
> All the help is more than welcome

Hope this helps,


Paul Bolle