[Pkg-erlang-devel] Bug#939804: Bug#939804: erlang: FTBFS on hppa - escript: exception error: bad argument

[John David Anglin]

On 2019-09-09 9:12 a.m., Sergei Golovan wrote:
> Hi John,
>
> On Mon, Sep 9, 2019 at 2:13 PM John David Anglin <dave.anglin at bell.net> wrote:
>> If you know how to reduce one of these regexp problems, I could look again.  Debugging
>> across forks is problematic (i.e., the error doesn't occur in escript).
> I seem to find the problematic code. If you look into
> erts/emulator/beam/erl_bif_re.c then
> you'll find the following lines after line 66:
>
> #define ERTS_PCRE_STACK_MARGIN (10*1024)
>
> #  define ERTS_STACK_LIMIT ((char *) ethr_get_stacklimit())
>
> static int
> stack_guard_downwards(void)
> {
>     char *limit = ERTS_STACK_LIMIT;
>     char c;
>
>     ASSERT(limit);
>
>     return erts_check_below_limit(&c, limit + ERTS_PCRE_STACK_MARGIN);
> }
>
> static int
> stack_guard_upwards(void)
> {
>     char *limit = ERTS_STACK_LIMIT;
>     char c;
>
>     ASSERT(limit);
>
>     return erts_check_above_limit(&c, limit - ERTS_PCRE_STACK_MARGIN);
> }
>
> void erts_init_bif_re(void)
> {
>     char c;
>     erts_pcre_malloc = &erts_erts_pcre_malloc;
>     erts_pcre_free = &erts_erts_pcre_free;
>     erts_pcre_stack_malloc = &erts_erts_pcre_stack_malloc;
>     erts_pcre_stack_free = &erts_erts_pcre_stack_free;
>     if ((char *) erts_ptr_id(&c) > ERTS_STACK_LIMIT)
>         erts_pcre_stack_guard = stack_guard_downwards;
>     else
>         erts_pcre_stack_guard = stack_guard_upwards;
>     default_table = NULL; /* ISO8859-1 default, forced into pcre */
>     max_loop_limit = CONTEXT_REDS * LOOP_FACTOR;
>
>     erts_init_trap_export(&re_exec_trap_export, am_erlang, am_re_run_trap, 3,
>                           &re_exec_trap);
>
>     grun_trap_exportp =  erts_export_put(am_re,am_grun,3);
>     urun_trap_exportp =  erts_export_put(am_re,am_urun,3);
>     ucompile_trap_exportp =  erts_export_put(am_re,am_ucompile,2);
>
>     return;
> }
>
> The code
>
>     if ((char *) erts_ptr_id(&c) > ERTS_STACK_LIMIT)
>         erts_pcre_stack_guard = stack_guard_downwards;
>     else
>         erts_pcre_stack_guard = stack_guard_upwards;
>
> has been introduces in version 20, and it is used to protect stack
> during PCRE calls.
> It seems that this stack protection doesn't work for hppa and always
> fails. As a result,
> every call to a regexp routine fails.
The calls fail with quit an obscure error.
>
> After I remove the erts_pcre_stack_guard assignment, Erlang started to
> build on hppa
> just fine.
>
> Unfortunately, I don't know anything about stack in hppa architecture,
> so I can't offer
> a proper fix in this case.
>
> I hope this'll help in debugging and developing a fix.
Awesome!

Stacks grows up on hppa, so this explains why only hppa fails.  Within gcc, there is no stack
protection for stacks that grow up.  Glibc provides a guard for each stack at upper end.  Kernel grows
main stack dynamically.  Initial allocation for main stack is fairly small.

I'll look at code tonight.  I wonder if limit is correct (ERTS_STACK_LIMIT).

Dave

-- 
John David Anglin  dave.anglin at bell.net