From: Alexis ROBERT <alexis.robert@gmail.com>
To: caml-list@yquem.inria.fr
Subject: Caml Light 0.8 and -fstrict-aliasing build issue
Date: Mon, 20 Jul 2009 14:58:09 +0200 [thread overview]
Message-ID: <4A6469E1.6050502@gmail.com> (raw)
Hello,
As the MPSI programme force us to use Caml Light instead of OCaml (our
teachers hit us each time we pronounce ocaml :) ), I tried to build the
sources on my computer, but during the build, I got this :
make[1]: Entering directory `/home/alexis/camllight/src/lib'
../camlrun ../camlcomp -stdlib . -O none -g -W string.mli
make[1]: *** [string.zi] Segmentation fault
More precisely, gdb told me that :
(gdb) run ../camlcomp -stdlib . -O none -g -W string.mli
Starting program: /home/alexis/camllight/src/camlrun ../camlcomp -stdlib
. -O none -g -W arg.mli
Program received signal SIGSEGV, Segmentation fault.
interprete (prog=0xe0e960 "\006\016") at interp.c:508
508 cur_instr = *pc++; <= In the real source code, that's Next;
I changed it with the macro content for more lisibility :)
(gdb) info locals
pc = (code_t) 0x9 <Address 0x9 out of bounds>
cur_instr = <value optimized out>
[...]
The reason of the segfaults seems to be linked with -fstrict-aliasing
(included in -O2, I discovered it when disabling gcc optimizations to
get cur_instr value). In fact, the weird thing is that pc pointer
suddently decreases to 0x09, which doesn't seem to be a very sweet
memory address, and causes a segfault in the Next macro when it
deferences pc.
I've tried to follow pc using a watchpoint before the magic change, but
it disables the watchpoint every time it reaches a segment of code where
pc is not defined which makes the debugging process *very* annoying :)
A workaround would be to use OPTS="-fno-strict-aliasing" in
runtime/Makefile line 5, but I don't know if it's very clean (or to
disable direct jumping but that's even worse :D ).
My computer is running Ubuntu 9.04 with gcc 4.3.3 and a x86_64 cpu (I
used the CVS version of caml light). It _MAY_ be a x86_64 only issue as
I vaguely remember a friend having the same configuration as mine using
Ubuntu x86 who has successfully built caml light, but I may have forgot
some details.
Thanks !
Alexis ROBERT
reply other threads:[~2009-07-20 12:58 UTC|newest]
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