Ok, I had success by removing “-debug” in favour of “-DDEBUG”. After compiling GHC I fired GDB and this is the output:

Starting program: /Users/adinapoli/programming/haskell/ghc/inplace/lib/bin/ghc-stage2 -B/Users/adinapoli/programming/haskell/ghc/inplace/lib --interactive

GHCi, version 8.3.20170413: http://www.haskell.org/ghc/ :? for help

[New Thread 0x120f of process 19786]

[New Thread 0x1403 of process 19786]

[New Thread 0x1503 of process 19786]

[New Thread 0x1603 of process 19786]

Thread 1 received signal SIGSEGV, Segmentation fault.

0x0000000104cdd81a in ocInit_MachO () at rts/linker/MachO.c:141

141 if(NULL != oc->info->nlist) {

Maybe it does ring a bell to any of you. In case not, I’m happy to continue digging.

On 14 April 2017 at 21:19, Alfredo Di Napoli <alfredo.dinapoli@gmail.com> wrote:

Hey Ben,

yes, it’s consistently reproducible. I have tried compiling GHC from scratch by adding `-dcore-lint` and `-debug` to GhcStage2HcOpts in my mk/build.mk, but eventually the build process failed with:

ld: library not found for -lHSrts_thr_debug_p

Any idea what am I doing wrong? Next I’m going to try enabling `-DDEBUG` only as described here:

https://ghc.haskell.org/trac/ghc/wiki/Debugging/Compiler

To see if I get any further.

Thanks!

A.

On 13 April 2017 at 19:01, Ben Gamari <ben@smart-cactus.org> wrote:
Alfredo Di Napoli <alfredo.dinapoli@gmail.com> writes:

> Hey all,
>
> I’m trying to compile GHC HEAD (cloning from master) with the `prof` build
> flavour on a Mac OS X 10.11.6 machine and I have noticed that, despite
> ghc-stage2 works as expected, when invoked with —interactive it starts
> before crashing with a segmentation fault:
>
> ```
> ☁ compiler [master] ⚡ ../inplace/bin/ghc-stage2 --interactive
> GHCi, version 8.3.20170413: http://www.haskell.org/ghc/ :? for help
> [1] 79176 segmentation fault ../inplace/bin/ghc-stage2 --interactive
> ```
>
> Did it happen to somebody else or it’s just me? Shall I try throwing gdb at
> it to try and see what’s going on?

Hmm, interesting. I've not seen crashes like this locally nor in CI. It
would be great if you could try to get some insight. Is this crash
perfectly reproducible?

It may be worth adding -dcore-lint to GhcStage2HcOpts to ensure the code
we are producing is sane.

Cheers,

- Ben