Building perf with clang

Building perf with clang

[Milian Wolff]

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Hey all,

I usually use clang to build my code, and have configured CC and CXX globally 
for that purpose. When I forget to unset that before I run "make" in the perf 
folder, I get into serious trouble as that is not supported at all.

So, can that be fixed, either by making perf buildable with clang, or by 
enforcing GCC within the Makefile if clang is not supported? Or at least error 
out early if clang would be used?

Thanks
-- 
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

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Re: Building perf with clang

[Arnaldo Carvalho de Melo]

Em Fri, Apr 01, 2016 at 11:19:05PM +0200, Milian Wolff escreveu:
> Hey all,
> 
> I usually use clang to build my code, and have configured CC and CXX globally 
> for that purpose. When I forget to unset that before I run "make" in the perf 
> folder, I get into serious trouble as that is not supported at all.
> 
> So, can that be fixed, either by making perf buildable with clang, or by 
> enforcing GCC within the Makefile if clang is not supported? Or at least error 
> out early if clang would be used?

I never tried, but I have it installed to test perf + BPF, so I'll try
it, fixing things as I go, patches welcome, as I'll start this tomorrow,
at the earliest.

- Arnaldo

Re: Building perf with clang

[Milian Wolff]

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On Freitag, 1. April 2016 19:16:02 CEST Arnaldo Carvalho de Melo wrote:
> Em Fri, Apr 01, 2016 at 11:19:05PM +0200, Milian Wolff escreveu:
> > Hey all,
> > 
> > I usually use clang to build my code, and have configured CC and CXX
> > globally for that purpose. When I forget to unset that before I run
> > "make" in the perf folder, I get into serious trouble as that is not
> > supported at all.
> > 
> > So, can that be fixed, either by making perf buildable with clang, or by
> > enforcing GCC within the Makefile if clang is not supported? Or at least
> > error out early if clang would be used?
> 
> I never tried, but I have it installed to test perf + BPF, so I'll try
> it, fixing things as I go, patches welcome, as I'll start this tomorrow,
> at the earliest.

Just FYI, this is the error I'm seeing:

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
CC=clang make
makeobj[0]: Entering directory `/home/milian/projects/src/linux/tools/perf'
  BUILD:   Doing 'make -j4' parallel build
warning: unknown warning option '-Wstrict-aliasing=3'; did you mean '-Wstring-
plus-int'? [-Wunknown-warning-option]
1 warning generated.

Auto-detecting system features:
...                         dwarf: [ on  ]
...                         glibc: [ on  ]
...                          gtk2: [ on  ]
...                      libaudit: [ on  ]
...                        libbfd: [ on  ]
...                        libelf: [ on  ]
...                       libnuma: [ on  ]
...        numa_num_possible_cpus: [ on  ]
...                       libperl: [ on  ]
...                     libpython: [ on  ]
...                      libslang: [ on  ]
...                     libcrypto: [ on  ]
...                     libunwind: [ on  ]
...            libdw-dwarf-unwind: [ on  ]
...                          zlib: [ on  ]
...                          lzma: [ on  ]
...                     get_cpuid: [ on  ]
...                           bpf: [ on  ]

  GEN      common-cmds.h
  CC       fixdep.o
cat: ./.fixdep.o.d: No such file or directory
/home/milian/projects/src/linux/tools/build/Makefile.build:77: recipe for 
target 'fixdep.o' failed
make[3]: *** [fixdep.o] Error 1
Makefile:36: recipe for target 'fixdep-in.o' failed
make[2]: *** [fixdep-in.o] Error 2
/home/milian/projects/src/linux/tools/build/Makefile.include:7: recipe for 
target 'fixdep' failed
make[1]: *** [fixdep] Error 2
make[1]: *** Waiting for unfinished jobs....
  PERF_VERSION = 4.2.rc6.g7a9420
make[1]: *** wait: No child processes.  Stop.
Makefile:68: recipe for target 'all' failed
make: *** [all] Error 2
makeobj[0]: Leaving directory `/home/milian/projects/src/linux/tools/perf'
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

I have no clue what's going on here, I never edit Makefiles by hand...

Speaking of Makefiles, how can I change the CFLAGS when building perf (with 
GCC)? I.e. how can I build it in -O0, or how can I enable sanitizers?

Thanks

-- 
Milian Wolff | milian.wolff@kdab.com | Software Engineer
KDAB (Deutschland) GmbH&Co KG, a KDAB Group company
Tel: +49-30-521325470
KDAB - The Qt Experts

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