[Libguestfs] nbdkit build failure (was: Re: jplesnik's nbdkit-1.35.5-4.fc39 failed to build)

[Jitka Plesnikova]

Thank you very much for your investigation.

Perl 5.38 is merge to rawhide now.

Regards;
Jitka


On 7/13/23 12:55, Richard W.M. Jones wrote:
> On Thu, Jul 13, 2023 at 11:03:35AM +0100, Richard W.M. Jones wrote:
>> On Thu, Jul 13, 2023 at 10:29:44AM +0100, Richard W.M. Jones wrote:
>>> It's a crash in Perl code, although called from the nbdkit perl plugin
>>> (C bindings).  Still debugging this ...
>>>
>>> Core was generated by `/home/rjones/d/nbdkit/server/nbdkit -U /tmp/nbdkittPN34a/sock -P /tmp/nbdkittPN'.
>>> Program terminated with signal SIGSEGV, Segmentation fault.
>>>
>>> warning: Section `.reg-xstate/150177' in core file too small.
>>> #0  Perl_my_snprintf (buffer=0x7f3a1e5fc630 "p\310_\036:\177", len=32,
>>>      format=0x7f3a1ef7e322 "_<(eval %lu)")
>>>      at /usr/src/debug/perl-5.38.0-499.fc39.x86_64/util.c:5248
>>> Downloading source file /usr/src/debug/perl-5.38.0-499.fc39.x86_64/util.c
>>> 5248            WITH_LC_NUMERIC_SET_TO_NEEDED(
>>> [Current thread is 1 (Thread 0x7f3a1e5fd6c0 (LWP 150177))]
>>> (gdb) bt
>>> #0  Perl_my_snprintf (buffer=0x7f3a1e5fc630 "p\310_\036:\177", len=32,
>>>      format=0x7f3a1ef7e322 "_<(eval %lu)")
>>>      at /usr/src/debug/perl-5.38.0-499.fc39.x86_64/util.c:5248
>> https://github.com/Perl/perl5/blob/ff7e37d5ca2e55a1e53e5b375e3cc9aedc9ce4ec/util.c#L5248
>>
>> Since its hardly obvious from the code, that macro expands to the
>> monster below.  I didn't bother to format it completely ...
>>
>> # 5245 "util.c"
>>      if (retval == -1) {
>>          do {
>> 	  void (*_restore_LC_NUMERIC_function)(PerlInterpreter* my_perl __attribute__((unused))) = ((void *)0);
>>            do {
>>             _Bool _in_lc_numeric = ((( ((
>>               _Bool
>>                 ) ((my_perl->Icompiling).cop_hints & 0x00000004)) || ( ((_Bool) ((my_perl->Icompiling).cop_hints & 0x00000010)) && Perl__is_in_locale_category(my_perl, (1), (
>>         1
>>         )))) || (((my_perl->Icurcop) && (((my_perl->Icurcop))->cop_hints + 0) & 0x00000004) || (((my_perl->Icurcop) && (((my_perl->Icurcop))->cop_hints + 0) & 0x00000010) && Perl__is_in_locale_category(my_perl, (0), (
>>         1
>>         ))))));
>>         ((void)0);
>>         if (_in_lc_numeric) {
>>           if ((! (my_perl->Inumeric_underlying) && (my_perl->Inumeric_standard) < 2)) { Perl_set_numeric_underlying(my_perl); _restore_LC_NUMERIC_function = &Perl_set_numeric_standard; }
>>          } else {
>> 	  if ((! (my_perl->Inumeric_standard))) { Perl_set_numeric_standard(my_perl); _restore_LC_NUMERIC_function = &Perl_set_numeric_underlying; } }
>>          } while (0);
>> 	retval = vsnprintf(buffer, len, format, ap);;
>> 	do { if (_restore_LC_NUMERIC_function) { _restore_LC_NUMERIC_function(my_perl); } ((void)0); } while (0);
>>          } while (0);
>>
>> ... because the fundamental problem is:
>>
>> (gdb) print my_perl
>> $13 = (PerlInterpreter *) 0x0
>>
>> so that's not gonna work.
> It turns out to be a bug in nbdkit!  A close reading of the perlembed
> man page reveals that we need to set the interpreter context when
> calling into Perl from a new thread.  The fix is:
>
> https://gitlab.com/nbdkit/nbdkit/-/commit/495708e9d1b396ff450df15d5789b4f6c51f6ebc
>
> I'll add this to Rawhide shortly.
>
> Rich.
>

-- 
Jitka Plesnikova
Senior Software Engineer
Red Hat