the default typemap doesn't always correctly handle get magic

[tonycoz]

Module:

Description

The default typemap lib/ExtUtils/typemap ships with perl and provides a default set of translations from SVs to the types requested by the XS code.

The T_PTRREF INPUT entry, for example:

T_PTRREF
        if (SvROK($arg)) {
            IV tmp = SvIV((SV*)SvRV($arg));
            $var = INT2PTR($type,tmp);
        }
        else
            Perl_croak_nocontext("%s: %s is not a reference",
                        ${$ALIAS?\q[GvNAME(CvGV(cv))]:\qq["$pname"]},
                        "$var")

doesn't perform any get magic before checking the ROK flag. If the supplied SV is tied, and SV has not previously been fetched or has changed since last fetched, the ROK flag may no longer be valid.

For the common case where a method is called on a T_PTRREF implemented object, method resolution will call get magic before the XSUB is called, so

I only demonstrate the issue in T_PTRREF here, other INPUT maps have similar problems, T_PTROBJ, T_REFREF seem to, but I haven't looked closely.

Steps to Reproduce

Needs to be run from a built source tree, since XS::Typemap isn't installed. I expect you could see similar results from many CPAN XS modules:

tony@venus:.../git/perl6$ cat ../typemap-magic.pl
use v5.40;
use XS::Typemap qw(T_PTRREF_IN T_PTRREF_OUT);
 
my $x;
 
tie my $y, "T";
 
my $i = 10;
my $p = T_PTRREF_OUT($i);
 
$x = 0;
my $ignored = $y; # prime $y
$x = $p;
$ignored = $y if @ARGV; # fetch
say T_PTRREF_IN($y);
 
package T {
  sub TIESCALAR ($class) { bless {}, $class }
  sub FETCH ($obj) { $x }
}
tony@venus:.../git/perl6$ ./perl -Ilib ../typemap-magic.pl
XS::Typemap::T_PTRREF_IN: ptr is not a reference at ../typemap-magic.pl line 15.
tony@venus:.../git/perl6$ ./perl -Ilib ../typemap-magic.pl FETCH
10

If you supply an argument like the second invocation, the magic is invoked by the assignment and T_PTRREF_IN() sees the correct value.

Expected behavior

The code completes successfully and prints 10 without the pre-fetch.

Perl configuration

# perl -V output goes here
Summary of my perl5 (revision 5 version 45 subversion 1) configuration:
  Commit id: f26eeb6cb5fed44b69135f7df58db3f187927356
  Platform:
    osname=linux
    osvers=6.12.85+deb13-amd64
    archname=x86_64-linux
    uname='linux venus 6.12.85+deb13-amd64 #1 smp preempt_dynamic debian 6.12.85-1 (2026-04-30) x86_64 gnulinux '
    config_args='-des -Dusedevel'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=undef
    usemultiplicity=undef
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O2'
    cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='14.2.0'
    gccosandvers=''
    intsize=4
    longsize=8
    ptrsize=8
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=16
    longdblkind=3
    ivtype='long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='off_t'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='cc'
    ldflags =' -fstack-protector-strong -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/x86_64-linux-gnu /usr/lib /usr/lib64
    libs=-lpthread -lgdbm -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
    libc=/lib/x86_64-linux-gnu/libc.so.6
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.41'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O2 -L/usr/local/lib -fstack-protector-strong'


Characteristics of this binary (from libperl): 
  Compile-time options:
    HAS_LONG_DOUBLE
    HAS_STRTOLD
    HAS_TIMES
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_HASH_FUNC_SIPHASH13
    PERL_HASH_USE_SBOX32
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_DEVEL
    PERL_USE_SAFE_PUTENV
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
  Built under linux
  Compiled at Jul 22 2026 10:52:15
  %ENV:
    PERLBREW_BASHRC_VERSION="0.43"
    PERLBREW_HOME="/home/tony/.perlbrew"
    PERLBREW_MANPATH=""
    PERLBREW_PATH="/home/tony/perl5/perlbrew/bin"
    PERLBREW_ROOT="/home/tony/perl5/perlbrew"
    PERLBREW_VERSION="0.67"
  @INC:
    lib
    /usr/local/lib/perl5/site_perl/5.45.1/x86_64-linux
    /usr/local/lib/perl5/site_perl/5.45.1
    /usr/local/lib/perl5/5.45.1/x86_64-linux
    /usr/local/lib/perl5/5.45.1

Edit: fix a mis-edit left from composition.

[jkeenan]

The default typemap lib/ExtUtils/typemap ships with perl and provides a default set of translati

Module:

Description ons from SVs to the types requested by the XS code.

Something's amiss in the paragraphs above.

[tonycoz]

Something's amiss in the paragraphs above.

Oops, fixed. I originally had the description text above the heading, it looks like I messed up the cut and paste to fix that.