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

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/ff7e37d5ca2e55a1e53e5b375e3cc9aedc9ce4... > > 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/495708e9d1b396ff450df15d5789b4f... I'll add this to Rawhide shortly. Rich.