Configuration option '-DPERL_POISON' not documented

[p5pRT]

Migrated from rt.perl.org#133727 (status was 'new')

Searchable as RT133727$

[p5pRT]

From @jkeenan

'-DPERL_POISON' is not currently documented in the core distribution.
Inquiring about this on #p5p, stsc pointed me to
http​://news.perlfoundation.org/2012/10/, wherein Nicholas discussed it
in the course of one of his monthly TPF grant reports​:

#####
The intent of -DPERL_POISON is to try scribble all over freed memory, to
spot use-after free errors (by promptly SEGVing).
#####

Can someone who is familiar with this option prepare some documentation
in, say, pod/perlhacktips.pod?

(My attention was drawn to this from this smoke-test report​:
http​://perl5.test-smoke.org/report/76043. Welcome back George Greer!)

Thank you very much.
Jim Keenan

[p5pRT]

From @jkeenan

Summary of my perl5 (revision 5 version 29 subversion 6) configuration​:
  Derived from​: c4df8c7
  Platform​:
  osname=linux
  osvers=4.15.0-42-generic
  archname=x86_64-linux
  uname='linux zareason 4.15.0-42-generic #45-ubuntu smp thu nov 15 19​:32​:57 utc 2018 x86_64 x86_64 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
  bincompat5005=undef
  Compiler​:
  cc='cc'
  ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64'
  optimize='-O2'
  cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector-strong -I/usr/local/include'
  ccversion=''
  gccversion='7.3.0'
  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/gcc/x86_64-linux-gnu/7/include-fixed /usr/include/x86_64-linux-gnu /usr/lib /lib/x86_64-linux-gnu /lib/../lib /usr/lib/x86_64-linux-gnu /usr/lib/../lib /lib /lib64 /usr/lib64
  libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.27.so
  so=so
  useshrplib=false
  libperl=libperl.a
  gnulibc_version='2.27'
  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_TIMES
  PERLIO_LAYERS
  PERL_COPY_ON_WRITE
  PERL_DONT_CREATE_GVSV
  PERL_MALLOC_WRAP
  PERL_OP_PARENT
  PERL_PRESERVE_IVUV
  PERL_USE_DEVEL
  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
  Locally applied patches​:
  uncommitted-changes
  Built under linux
  Compiled at Dec 15 2018 10​:22​:19
  %ENV​:
  PERL2DIR="/home/jkeenan/gitwork/perl2"
  PERLBREW_HOME="/home/jkeenan/.perlbrew"
  PERLBREW_MANPATH="/home/jkeenan/perl5/perlbrew/perls/perl-5.28.0/man"
  PERLBREW_PATH="/home/jkeenan/perl5/perlbrew/bin​:/home/jkeenan/perl5/perlbrew/perls/perl-5.28.0/bin"
  PERLBREW_PERL="perl-5.28.0"
  PERLBREW_ROOT="/home/jkeenan/perl5/perlbrew"
  PERLBREW_SHELLRC_VERSION="0.84"
  PERLBREW_VERSION="0.84"
  PERL_WORKDIR="/home/jkeenan/gitwork/perl"
  @​INC​:
  lib
  /usr/local/lib/perl5/site_perl/5.29.6/x86_64-linux
  /usr/local/lib/perl5/site_perl/5.29.6
  /usr/local/lib/perl5/5.29.6/x86_64-linux
  /usr/local/lib/perl5/5.29.6

[jkeenan]

From @jkeenan

'-DPERL_POISON' is not currently documented in the core distribution. Inquiring about this on #p5p, stsc pointed me to http​://news.perlfoundation.org/2012/10/, wherein Nicholas discussed it in the course of one of his monthly TPF grant reports​:

The intent of -DPERL_POISON is to try scribble all over freed memory, to spot use-after free errors (by promptly SEGVing).

Can someone who is familiar with this option prepare some documentation in, say, pod/perlhacktips.pod?

(My attention was drawn to this from this smoke-test report​: http​://perl5.test-smoke.org/report/76043. Welcome back George Greer!)

Thank you very much. Jim Keenan

@nwc10, could you take a look at this ticket?