sort() optimization mishandles numeric comparison between overloaded values

[tonycoz]

Module:

Description

sort's internal version of the { $a <=> $b } block mishandles fallback comparison of large integer overloaded values.

Found when working on numeric comparison APIs for #23918

Steps to Reproduce

# not properly sorted:
$ perl -le 'package Big { use overload "0+" => sub { $_[0][0] }, fallback => 1; } my @x = ( bless([~0], "Big"), bless([~0-1], "Big")); print for sort { $a <=> $b } @x'
18446744073709551615
18446744073709551614

If you prevent the optimisation:

$ perl -le 'package Big { use overload "0+" => sub { $_[0][0] }, fallback => 1; } my @x = ( bless([~0], "Big"), bless([~0-1], "Big")); print for sort { $a <=> 0+$b } @x'
18446744073709551614
18446744073709551615

Expected behavior

Correct comparison in the various amagic comparison functions in pp_sort.c.

Perl configuration

(also in system perl 5.40 and blead)

Summary of my perl5 (revision 5 version 42 subversion 0) configuration:
   
  Platform:
    osname=linux
    osvers=6.1.0-40-amd64
    archname=x86_64-linux-thread-multi
    uname='linux venus 6.1.0-40-amd64 #1 smp preempt_dynamic debian 6.1.153-1 (2025-09-20) x86_64 gnulinux '
    config_args='-des -DDEBUGGING -Doptimize=-O1 -ggdb3 -Dprefix=/home/tony/perl/v5.42.0-debug -Dusethreads'
    hint=recommended
    useposix=true
    d_sigaction=define
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=define
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
  Compiler:
    cc='cc'
    ccflags ='-D_REENTRANT -D_GNU_SOURCE -fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64 -D_FORTIFY_SOURCE=2'
    optimize='-O1 -ggdb3'
    cppflags='-D_REENTRANT -D_GNU_SOURCE -fwrapv -DDEBUGGING -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
    ccversion=''
    gccversion='12.2.0'
    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='2.36'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs
    dlext=so
    d_dlsymun=undef
    ccdlflags='-Wl,-E'
    cccdlflags='-fPIC'
    lddlflags='-shared -O1 -ggdb3 -L/usr/local/lib -fstack-protector-strong'
 
 
Characteristics of this binary (from libperl): 
  Compile-time options:
    DEBUGGING
    HAS_LONG_DOUBLE
    HAS_STRTOLD
    HAS_TIMES
    MULTIPLICITY
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_HASH_FUNC_SIPHASH13
    PERL_HASH_USE_SBOX32
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_TRACK_MEMPOOL
    PERL_USE_SAFE_PUTENV
    USE_64_BIT_ALL
    USE_64_BIT_INT
    USE_ITHREADS
    USE_LARGE_FILES
    USE_LOCALE
    USE_LOCALE_COLLATE
    USE_LOCALE_CTYPE
    USE_LOCALE_NUMERIC
    USE_LOCALE_TIME
    USE_PERLIO
    USE_PERL_ATOF
    USE_REENTRANT_API
    USE_THREAD_SAFE_LOCALE
  Built under linux
  Compiled at Oct 29 2025 22:32:30
  %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:
    /home/tony/perl/v5.42.0-debug/lib/site_perl/5.42.0/x86_64-linux-thread-multi
    /home/tony/perl/v5.42.0-debug/lib/site_perl/5.42.0
    /home/tony/perl/v5.42.0-debug/lib/5.42.0/x86_64-linux-thread-multi
    /home/tony/perl/v5.42.0-debug/lib/5.42.0