perlcdelta - what is new for cperl v5.29.1


This document describes differences between the cperl 5.29.1 and the cperl 5.29.0 release.

If you are upgrading from an earlier release such as v5.28.1c, first read perl5290cdelta, which describes differences between v5.28.1c and v5.29.0c.


[CVE-2018-18311] Integer overflow leading to buffer overflow and segmentation fault

Integer arithmetic in Perl_my_setenv() could wrap when the combined length of the environment variable name and value exceeded around 0x7fffffff. This could lead to writing beyond the end of an allocated buffer with attacker supplied data.

[perl #133204]

Restrict my_setenv to ARG_MAX

perl5 fixed Perl_my_setenv() by allowing %ENV sizes larger than ARG_MAX (typically 128Kb), up to 2GB. This is considered a security risk. It writes onto the kernel stack, even if often caught by MAXEXECARGS "Argument list too long" kernel errors on the next exec call. cperl disallows %ENV larger than the sysconf(_SC_ARG_MAX)/MAX_ARG_STRLEN/ ARG_MAX/NCARGS size with a new "Environment size %d larger than the allowed %d" in perldiag error.

Performance Enhancements

Modules and Pragmata

The list of new and updated modules is modified automatically as part of preparing a Perl release, so the only reason to manually add entries here is if you're summarising the important changes in the module update. (Also, if the manually-added details don't match the automatically-generated ones, the release manager will have to investigate the situation carefully.)

Updated Modules and Pragmata

B::C 1.55_10

Better mconcat support. Fix some XS memory leaks.

Add missing optimize flags to cc_harness, and perlcc, required for -flto.

When testing overly large C files > 50k (with modules), apply cc -O1, not -O2 or -O3.

Honor and set SKIP_SLOW_TESTS, set with -flto. Applied to all tests with large C files. t/c*.t now only execute 13 tests under -flto/SKIP_SLOW_TESTS and CI, because they may not be finished in under 10min.

Added a is_CI() test detection.

Cpanel::JSON::XS 4.09

Silence Gconvert -Wunused-result.

Add unblessed_bool property (PR #118 by Pali)

Add seperate allow_dupkeys property, in relaxed (#122), Fixed allow_dupkeys for the XS slow path, Silence 2 -Wunused-value warnings, Fix ->unblessed_bool to produce modifiable perl structures (PR #121 by Pali).

ExtUtils::Embed 1.36

Added optimize to ccopts, required for -flto. Fixed documentation of ccopts. Fixed test to use ccopts, include local -I.., indentation, remove wrong -O hack.

ExtUtils::MakeMaker 8.35_08

Added -flto support for static libs (need the lto plugin) and D for deterministic builds, using arflags for AR_STATIC_ARGS, not just 'cr'.

fix FULLPERL for win32 cperl

Storable 1.12_04

Fix stacklimit security issues introduced in the p5p release [cperl #393]. User limits must not be higher than the probed hard limits, when overridden by user code or data, via hooks or even pst data.

Win32 0.52_02

Fix various -Wunused warnings, added () usage croaks. Fixed a -Warray-bounds buffer overflow in LONGPATH, and two -Wmaybe-uninitialized.


Changes to Existing Documentation

We have attempted to update the documentation to reflect the changes listed in this document. If you find any we have missed, send email to

Additionally, the following selected changes have been made:


Configuration and Compilation


Tests were added and changed to reflect the other additions and changes in this release. Furthermore, these significant changes were made:

Platform Support

Platform-Specific Notes


Fixed boot_Win32CORE prototype to skip dllexport, fatal with -flto.

Fixed ar for Win32CORE.a by using the gcc liblto plugin.

Skip probing for -flto on cygwin. This reliably fails to find a proper image-base with that many new symbols, the adress space is just too small: Invalid relocation. Offset 0x.. at address 0x.. doesn't fit into 32 bits

Internal Changes


Selected Bug Fixes


cperl 5.29.1 represents approximately 5 months of development since cperl 5.29.0c and contains approximately 15,000 lines of changes across 140 files from 4 authors.

Excluding auto-generated files, documentation and release tools, there were approximately 1,200 lines of changes to 52 .pm, .t, .c and .h files.

The following people are known to have contributed the improvements that became cperl 5.29.1:

Reini Urban, David Mitchell, Dominic Hargreaves, Karl Williamson.

The list above is almost certainly incomplete as it is automatically generated from version control history including the perl and cperl repos. In particular, it does not include the names of the (very much appreciated) contributors who reported issues to the Perl bug tracker and the cperl github issues.

Many of the changes included in this version originated in the CPAN modules included in Perl's core. We're grateful to the entire CPAN community for helping Perl to flourish.

For a more complete list of all of Perl's historical contributors, please see the AUTHORS file in the Perl source distribution.

Generated with:

    cperl Porting/ cperl-5.29.0..HEAD -c

Reporting Bugs

If you find what you think is a bug, you might check the perl bug database at . There may also be information at , the Perl Home Page.

If you believe you have an unreported bug, please run the cperlbug program included with your release. Be sure to trim your bug down to a tiny but sufficient test case. Your bug report, along with the output of perl -V, will be sent off to to be analysed by the Perl porting team.

If you think it's a cperl specific bug or trust the cperl developers more please file an issue at

If the bug you are reporting has security implications which make it inappropriate to send to a publicly archived mailing list, then see "SECURITY VULNERABILITY CONTACT INFORMATION" in perlsec For details of how to report the issue.


The Changes file for an explanation of how to view exhaustive details on what changed.

The INSTALL file for how to build Perl.

The README file for general stuff.

The Artistic and Copying files for copyright information.