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Re: [XS] Weird behaviour on some Linux systems

by Corion (Pope)
on Oct 10, 2019 at 12:15 UTC ( #11107303=note: print w/replies, xml ) Need Help??


in reply to [XS] Weird behaviour on some Linux systems

My unfounded random guess would be that on the problematic system, Perl brings its own implementation of sprintf and the OS (or C-lib) implementation of printf differs from the Perl-supplied implementation.

I assume that if you watch the output of ./Configure closely enough you can find what it thinks about the (un)availability of sprintf and how it replaces those.

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Re^2: [XS] Weird behaviour on some Linux systems
by syphilis (Bishop) on Oct 10, 2019 at 13:35 UTC
    Thanks for the quick feedback, Corion ... not so sure that you're on the right track, but I certainly can't prove otherwise.

    Here's a clearer demo that contains only one instance of "sprintf", and no occurrences of "printf":
    use strict; use warnings; use Devel::Peek; use Inline C => Config => BUILD_NOISY => 1, ; use Inline C => <<'EOC'; SV * foo(SV * arg) { SV * keysv; keysv = NEWSV(0, 32); /* Make sure arg is an NV */ if(!SvNOK(arg)) croak("Not a valid arg passed to foo for this demo") +; sv_setpvf(keysv, "%.19" NVgf, SvNV(arg)); return keysv; } SV * bar(SV * arg) { SV * keysv; char buff[30]; keysv = NEWSV(0, 32); /* Make sure arg is an NV */ if(!SvNOK(arg)) croak("Not a valid arg passed to bar for this demo" +); sprintf(buff, "%.19" NVgf, SvNV(arg)); sv_setpvf(keysv, "%s", buff); return keysv; } EOC my $sv_foo = foo(2 ** 63); my $sv_bar = bar(2 ** 63); Dump $sv_foo; print "#####################\n"; Dump $sv_bar;
    On Windows 7 it produces (sanely, IMO):
    SV = PV(0x72be48) at 0x39bfb8 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x33b748 "9223372036854775808"\0 CUR = 19 LEN = 34 ##################### SV = PV(0x72be98) at 0x33c638 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x33b8d8 "9223372036854775808"\0 CUR = 19 LEN = 34
    On Ubuntu-18.04 I see the (insane) output of:
    SV = PV(0x56545ac36fd0) at 0x56545ac5b728 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x56545ac57170 "9.2233720368547758e+18"\0 CUR = 22 LEN = 34 ##################### SV = PV(0x56545ac37070) at 0x56545acb8178 REFCNT = 1 FLAGS = (POK,pPOK) PV = 0x56545b64be20 "9223372036854775808"\0 CUR = 19 LEN = 34
    Interestingly, on Ubuntu, it's the XSub containing the "sprintf" call that's producing the sane result.
    (At least, it's producing the output that I expect and want ;-)

    Cheers,
    Rob

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