BBC: Blead Breaks BSON

[cjg-cguevara]

This is a bug report for perl from "Carlos Guevara" carlos@carlosguevara.com,
generated with the help of perlbug 1.43 running under perl 5.41.7.

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BBC: Blead Breaks BSON

Please see http://fast-matrix.cpantesters.org/?dist=BSON

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Flags

• category=core
• severity=low

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Perl configuration

Site configuration information for perl 5.41.7:

Configured by cpan at Thu Dec 19 00:23:29 EST 2024.

Summary of my perl5 (revision 5 version 41 subversion 7) configuration:
  Commit id: 7496ff12fc1a5176641e424139fc7ad8e8ca08e5
  Platform:
    osname=linux
    osvers=5.14.0-503.16.1.el9_5.x86_64
    archname=x86_64-linux
    uname='linux cjg-rhel9 5.14.0-503.16.1.el9_5.x86_64 #1 smp preempt_dynamic thu nov 21 07:26:21 est 2024 x86_64 x86_64 x86_64 gnulinux '
    config_args='-des -Dprefix=/home/cpan/bin/perl -Dscriptdir=/home/cpan/bin/perl/bin -Dusedevel -Duse64bitall'
    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='11.5.0 20240719 (Red Hat 11.5.0-2)'
    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 /usr/lib64 /usr/local/lib64
    libs=-lpthread -ldb -ldl -lm -lcrypt -lutil -lc
    perllibs=-lpthread -ldl -lm -lcrypt -lutil -lc
    libc=/lib/../lib64/libc.so.6
    so=so
    useshrplib=false
    libperl=libperl.a
    gnulibc_version='2.34'
  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'


---
@INC for perl 5.41.7:
    /home/cpan/bin/perl/lib/site_perl/5.41.7/x86_64-linux
    /home/cpan/bin/perl/lib/site_perl/5.41.7
    /home/cpan/bin/perl/lib/5.41.7/x86_64-linux
    /home/cpan/bin/perl/lib/5.41.7

---
Environment for perl 5.41.7:
    HOME=/home/cpan
    LANG=en_US.UTF-8
    LANGUAGE (unset)
    LC_ALL=C
    LD_LIBRARY_PATH (unset)
    LOGDIR (unset)
    PATH=/home/cpan/bin/perl/bin:/home/cpan/bin:/usr/share/Modules/bin:/usr/local/bin:/usr/bin:/usr/local/sbin:/usr/sbin
    PERL_BADLANG (unset)
    SHELL=/bin/bash

[jkeenan]

Bisecting with the following invocation:

perl Porting/bisect.pl \
--start=6f836886eca09c5df3a9f985231636e29b8f10dc \
--end=7496ff12fc1a5176641e424139fc7ad8e8ca08e5 \
--module=BSON

... pointed to this as the breaking point:

fbebf96ce083dc15b63c04d5695997d6e2657b03 is the first bad commit
commit fbebf96ce083dc15b63c04d5695997d6e2657b03
Author: Richard Leach <richardleach@users.noreply.github.com>
Date:   Wed Oct 23 23:32:04 2024 +0000
Commit:     Richard Leach <rich+perl@hyphen-dash-hyphen.info>
CommitDate: Mon Dec 16 21:33:09 2024 +0000

    Perl_sv_setsv_flags: handle mixed IV and NV fast case
    
    When the fast code at the start of Perl_sv_setsv_flags was modified to
    also support bodyless NVs, the simplest possible change was made.
    However, this meant that there was no fast handling when one SV was an
    IV and the other a NV. Actually having this seems desirable since it
    avoids the need to allocate (and later release) an XPVIV or XPVNV body.

 sv.c | 6 +++++-
 1 file changed, 5 insertions(+), 1 deletion(-)
bisect found first bad commit
That took 1579 seconds.

@richardleach, can you take a look? Thanks.

[mauke]

For reference, this is the error/failing test:

t/mapping/double.t ............... Possible precedence problem between ! and string eq at /home/mauke/.cpan/build/BSON-v1.12.2-1/blib/lib/BSON.pm line 99.
t/mapping/double.t ............... 1/?                                                                                                                                                                                                       
#   Failed test 'Inf as double->double' 
#   at t/mapping/double.t line 55.                                                                                                                                                                                                           
#          got: 'NV'                     
#     expected: 'PVNV'
                                                           
#   Failed test '-Inf as double->double'
#   at t/mapping/double.t line 55.                                                                                    
#          got: 'NV'                   
#     expected: 'PVNV'   
                                                                                                                      
#   Failed test 'NaN as double->double'
#   at t/mapping/double.t line 55.                
#          got: 'NV'                             
#     expected: 'PVNV'       
                                                           
#   Failed test 'Inf as BSON::Double->BSON::Double'                                                                   
#   at t/mapping/double.t line 69.   
#          got: 'NV'       
#     expected: 'PVNV'                                                                                                

#   Failed test '-Inf as BSON::Double->BSON::Double'
#   at t/mapping/double.t line 69.
#          got: 'NV'
#     expected: 'PVNV'

#   Failed test 'NaN as BSON::Double->BSON::Double'
#   at t/mapping/double.t line 69.
#          got: 'NV'
#     expected: 'PVNV'
# Looks like you failed 6 tests of 39.
t/mapping/double.t ............... Dubious, test returned 6 (wstat 1536, 0x600)
Failed 6/39 subtests 

... which I'm pretty sure is just the module relying on implementation details that it shouldn't rely on. In this case, it tests that bson_decode(bson_encode($x)) (for $x = Inf, -Inf, NaN) returns floating-point values represented as PVNV instead of the (slimmer) NV.

(To be honest, I can't figure out why Perl would use PVNV here in the first place, and running the test in the perl debugger makes it use PVMG instead.)

[Leont]

which I'm pretty sure is just the module relying on implementation details that it shouldn't rely on

Agreed.

[richardleach]

In this case, it tests that bson_decode(bson_encode($x)) (for $x = Inf, -Inf, NaN) returns floating-point values represented as PVNV instead of the (slimmer) NV.

Yes, and a portable fix seems straightforward:

diff --git a/BSON-v1.12.2/t/mapping/double.t b/BSON-v1.12.2_patched/t/mapping/double.t
index fb0d51b..fdb0c86 100644
--- a/BSON-v1.12.2/t/mapping/double.t
+++ b/BSON-v1.12.2_patched/t/mapping/double.t
@@ -50,9 +50,12 @@ my %special = (
     "NaN"  => BSON::Double::NaN(),
 );
 
+my $iv2nv_type = 0; $iv2nv_type = 1.1; $iv2nv_type = sv_type($iv2nv_type);
+
+
 for my $s ( qw/Inf -Inf NaN/ ) {
     $hash = decode( encode( { A => $special{$s} } ) );
-    is( sv_type( $hash->{A} ), 'PVNV', "$s as double->double" );
+    is( sv_type( $hash->{A} ), $iv2nv_type, "$s as double->double" );
     packed_is( FLOAT, $hash->{A}, $special{$s}, "value correct" );
 }
 
@@ -66,7 +69,7 @@ for my $s ( qw/Inf -Inf NaN/ ) {
 # test special BSON::Double
 for my $s ( qw/Inf -Inf NaN/ ) {
     $hash = decode( encode( { A => bson_double($special{$s}) } ) );
-    is( sv_type( $hash->{A} ), 'PVNV', "$s as BSON::Double->BSON::Double" );
+    is( sv_type( $hash->{A} ), $iv2nv_type, "$s as BSON::Double->BSON::Double" );
     packed_is( FLOAT, $hash->{A}, $special{$s}, "value correct" );
 }

The problem for this module is that it's been abandoned. https://metacpan.org/pod/BSON says:

"Version v1.12.0 was the final feature release of the MongoDB BSON library and version v1.12.2 is the final patch release.

As of August 13, 2020, the MongoDB Perl driver and related libraries have reached end of life and are no longer supported by MongoDB. See the August 2019 deprecation notice for rationale." The repository has been made read-only: https://github.com/mongodb-labs/mongo-perl-bson

I don't know where to send the patch, or if a supported fork of this module exists.

[jkeenan]

In this case, it tests that bson_decode(bson_encode($x)) (for $x = Inf, -Inf, NaN) returns floating-point values represented as PVNV instead of the (slimmer) NV.

Yes, and a portable fix seems straightforward:

diff --git a/BSON-v1.12.2/t/mapping/double.t b/BSON-v1.12.2_patched/t/mapping/double.t
index fb0d51b..fdb0c86 100644
--- a/BSON-v1.12.2/t/mapping/double.t
+++ b/BSON-v1.12.2_patched/t/mapping/double.t
@@ -50,9 +50,12 @@ my %special = (
     "NaN"  => BSON::Double::NaN(),
 );
 
+my $iv2nv_type = 0; $iv2nv_type = 1.1; $iv2nv_type = sv_type($iv2nv_type);
+
+
 for my $s ( qw/Inf -Inf NaN/ ) {
     $hash = decode( encode( { A => $special{$s} } ) );
-    is( sv_type( $hash->{A} ), 'PVNV', "$s as double->double" );
+    is( sv_type( $hash->{A} ), $iv2nv_type, "$s as double->double" );
     packed_is( FLOAT, $hash->{A}, $special{$s}, "value correct" );
 }
 
@@ -66,7 +69,7 @@ for my $s ( qw/Inf -Inf NaN/ ) {
 # test special BSON::Double
 for my $s ( qw/Inf -Inf NaN/ ) {
     $hash = decode( encode( { A => bson_double($special{$s}) } ) );
-    is( sv_type( $hash->{A} ), 'PVNV', "$s as BSON::Double->BSON::Double" );
+    is( sv_type( $hash->{A} ), $iv2nv_type, "$s as BSON::Double->BSON::Double" );
     packed_is( FLOAT, $hash->{A}, $special{$s}, "value correct" );
 }

The problem for this module is that it's been abandoned. https://metacpan.org/pod/BSON says:

"Version v1.12.0 was the final feature release of the MongoDB BSON library and version v1.12.2 is the final patch release.

As of August 13, 2020, the MongoDB Perl driver and related libraries have reached end of life and are no longer supported by MongoDB. See the August 2019 deprecation notice for rationale." The repository has been made read-only: https://github.com/mongodb-labs/mongo-perl-bson

I don't know where to send the patch, or if a supported fork of this module exists.

Okay, provided we understand how the breaking commit actually broke the module's tests, we don't have to worry too much about this. We should probably focus on #22866 (B-Utils).