O2 fails to be built on MAC Mojave (clang error)

Dear all,
I have problems to buid O2 since few days, after some updates (of brew, alidist…)log.txt (96.7 KB)
The error is in the log attached here,
and it seems to be something related to:
clang: error: unable to execute command: Illegal instruction: 4
I use this command:
aliBuild build QualityControl --defaults o2

Do you have any hints?
thanks in advance,


The log is cryptic, googling suggests that the clang: error: unable to execute command: Illegal instruction: 4 is related to optimisation, but Cristina tried to rebuild with add_compile_options(-O0 -g -fPIC) , getting exactly the same failure. I’ve checked the RawPixelDecoder code and don’t see anything wrong there, on ubuntu there are no any warnings.

I’ve uploaded the files mentioned in log (provided by Cristina):

clang: note: diagnostic msg: /var/folders/8p/1sqt0xtx08zdzx99b92tlhb80000gn/T/RawPixelDecoder-26f245.cpp
clang: note: diagnostic msg: /var/folders/8p/1sqt0xtx08zdzx99b92tlhb80000gn/T/RawPixelDecoder-26f245.sh
clang: note: diagnostic msg: Crash backtrace is located in
clang: note: diagnostic msg: /Users/criter3/Library/Logs/DiagnosticReports/clang_<YYYY-MM-DD-HHMMSS>_<hostname>.crash

to https://cernbox.cern.ch/index.php/s/xKaa5xeLDeC2Lp4

@eulisse @swenzel do you have any idea what could produce such an error? Is Mojave supported at all?


I see the XCode version is 10.0.1 (1001.0.46). I would start by updating to the lastest one (I’ve 11.5 on my box). What mac is this?

Hello Giulio,

my MAC is MacBook Pro OS Mojave 10.14.6.
If I update XCode, then I should just rebuild everything, also AliPhysics, right?

Can you have a look at:

and report the exact version of the hardware you have?

Hello Giulio,
it should be 10.14.6 (18G103)


I meant the line below… :wink:

and also the processor would help.

it should be everything! :slight_smile:

Yes, and it’s modern enough actually… :-/ Can you update Xcode and recompile?

Hello Giulio,
it seems that I cannot update XCode to the latest version,
so I should update the OS to Catalina maybe, or try an intermediate version of XCode.


I am quite sure that I installed Xcode 11 before MacOS Catalina, but maybe the latest Xcode 11 versions (11.6) in the app store require Catalina while older versions were maybe still compatible with Mojave. One can download older versions here: https://developer.apple.com/download/more/ but I am not sure this will work. It is probably the easiest to upgrade to Catalina - it should fully support ALICE software for both run1/2 and run3. However in case this would be required offline should update the macOS support policy, because up to now both the latest and the previous version are officially supported.




I had the same issue as @cterrevo on MacOS 10.14.

I confirm that after I upgraded to MacOS 10.15, O2 built successfully.