From @dcollinsn

perl -V​:

W​:\buildbot\windows1\win32\build\t>perl -I../lib -V
Summary of my perl5 (revision 5 version 25 subversion 3) configuration​:

  Platform​:
  osname=MSWin32
  osvers=10.0
  archname=MSWin32-x86-multi-thread
  uname=''
  config_args='undef'
  hint=recommended
  useposix=true
  d_sigaction=undef
  useithreads=define
  usemultiplicity=define
  use64bitint=undef
  use64bitall=undef
  uselongdouble=undef
  usemymalloc=n
  bincompat5005=undef
  Compiler​:
  cc='gcc'
  ccflags =' -s -O2 -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DPERL_IMPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -fwrapv -fno-strict-aliasing -mms-bitfields'
  optimize='-s -O2'
  cppflags='-DWIN32'
  ccversion=''
  gccversion='4.9.3'
  gccosandvers=''
  intsize=4
  longsize=4
  ptrsize=4
  doublesize=8
  byteorder=1234
  doublekind=3
  d_longlong=define
  longlongsize=8
  d_longdbl=define
  longdblsize=12
  longdblkind=3
  ivtype='long'
  ivsize=4
  nvtype='double'
  nvsize=8
  Off_t='long long'
  lseeksize=8
  alignbytes=8
  prototype=define
  Linker and Libraries​:
  ld='g++'
  ldflags ='-s -L"c​:\perl\lib\CORE" -L"C​:\MinGW\lib"'
  libpth=C​:\MinGW\lib
  libs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
  perllibs=-lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversion -lodbc32 -lodbccp32 -lcomctl32
  libc=
  so=dll
  useshrplib=true
  libperl=libperl525.a
  gnulibc_version=''
  Dynamic Linking​:
  dlsrc=dl_win32.xs
  dlext=dll
  d_dlsymun=undef
  ccdlflags=' '
  cccdlflags=' '
  lddlflags='-mdll -s -L"c​:\perl\lib\CORE" -L"C​:\MinGW\lib"'

Characteristics of this binary (from libperl)​:
  Compile-time options​:
  HAS_TIMES
  HAVE_INTERP_INTERN
  MULTIPLICITY
  PERLIO_LAYERS
  PERL_COPY_ON_WRITE
  PERL_DONT_CREATE_GVSV
  PERL_HASH_FUNC_ONE_AT_A_TIME_HARD
  PERL_IMPLICIT_CONTEXT
  PERL_IMPLICIT_SYS
  PERL_MALLOC_WRAP
  PERL_OP_PARENT
  PERL_PRESERVE_IVUV
  USE_ITHREADS
  USE_LARGE_FILES
  USE_LOCALE
  USE_LOCALE_COLLATE
  USE_LOCALE_CTYPE
  USE_LOCALE_NUMERIC
  USE_LOCALE_TIME
  USE_PERLIO
  USE_PERL_ATOF
  Built under MSWin32
  Compiled at Jul 16 2016 17​:21​:19
  @​INC​:
  ../lib
  W​:/buildbot/windows1/win32/build/t/lib
  .

This is blead revision f6203e9 built by mingw.org GCC 4.9.3

W​:\buildbot\windows1\win32\build\t>perl -I../lib harness ../lib/warnings.t
../lib/warnings.t .. 242/899 PROG​:
use warnings 'uninitialized';
my ($v);

# check hash key is sanitised
my %h = ("\0011\002\r\n\t\f\"\\\x{1234}abcdefghijklmnopqrstuvwxyz", undef);
$v = join '', %h;
EXPECTED​:
Use of uninitialized value $h{"\0011\2\r\n\t\f\"\\\x{1234}abcde"...} in join or string at - line 6.
GOT​:
Use of uninitialized value $h{"\11\2\r\n\t\f\"\\\x{1234}abcdefg"...} in join or string at - line 6.
# Failed test 279 - at lib\warnings\9uninit line 1159
../lib/warnings.t .. Failed 1/899 subtests
  (less 1 skipped subtest​: 897 okay)

Test Summary Report

../lib/warnings.t (Wstat​: 0 Tests​: 899 Failed​: 1)
  Failed test​: 279
Files=1, Tests=899, 20 wallclock secs ( 0.17 usr + 0.00 sys = 0.17 CPU)
Result​: FAIL

As with RT #128638, this is a warnings issue on mingw.org compilers. mingw-w64.org compilers do not exhibit this error, either on 32-bit or 64-bit builds, nor am I seeing this test failure on Cygwin or Linux.

--
Respectfully,
Dan Collins

From @dcollinsn

This test failure appears to be from the same root cause as the above - printing escape sequences vs leading zeros. It has the same compiler association - mingw.org only, all configurations.

# Failed test 'STASH for blessed hashrefs is correct'
# at t/Peek.t line 1331.
# 'SV = IV(0x192aa90) at 0x192aa94
# REFCNT = 1
# FLAGS = (ROK)
# RV = 0x1929e14
# SV = PVHV(0x17d5bbc) at 0x1929e14
# REFCNT = 1
# FLAGS = (OBJECT,SHAREKEYS)
# STASH = 0x192ac24 "\0​::\x{1}​::\x{30cd}"
# ARRAY = 0x0
# KEYS = 0
# FILL = 0
# MAX = 7
# '
# doesn't match '(?^​:STASH = 0x[[​:xdigit​:]]+\s+\"\\0\​:\​:\\x\{01\}\​:\​:\\x\{30cd\}\")'

# Failed test 'PROTOTYPE is escaped correctly'
# at t/Peek.t line 1338.
# 'SV = IV(0x1929ea0) at 0x1929ea4
# REFCNT = 1
# FLAGS = (ROK)
# RV = 0x194
# SV = PVCV(0x198f49c) at 0x194
# REFCNT = 2
# FLAGS = (POK,pPOK,DYNFILE,UTF8)
# PROTOTYPE = "\0\x{1}\x{30cd}"
# COMP_STASH = 0xdf6b54 "main"
# ROOT = 0x0
# GVGV​::GV = 0x194 "main" :​: "doof"
# FILE = "t/Peek.t"
# DEPTH = 0
# FLAGS = 0x1000
# OUTSIDE_SEQ = 0
# PADLIST = 0x0
# OUTSIDE = 0x0 (null)
# '
# doesn't match '(?^​:PROTOTYPE = \"\\0\\x\{01\}\\x\{30cd\}\")'
# Looks like you failed 2 tests of 112.
../ext/Devel-Peek/t/Peek.t .........................................
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/112 subtests
  (less 2 skipped subtests​: 108 okay)

--
Respectfully,
Dan Collins

From [Unknown Contact. See original ticket]

This test failure appears to be from the same root cause as the above - printing escape sequences vs leading zeros. It has the same compiler association - mingw.org only, all configurations.

# Failed test 'STASH for blessed hashrefs is correct'
# at t/Peek.t line 1331.
# 'SV = IV(0x192aa90) at 0x192aa94
# REFCNT = 1
# FLAGS = (ROK)
# RV = 0x1929e14
# SV = PVHV(0x17d5bbc) at 0x1929e14
# REFCNT = 1
# FLAGS = (OBJECT,SHAREKEYS)
# STASH = 0x192ac24 "\0​::\x{1}​::\x{30cd}"
# ARRAY = 0x0
# KEYS = 0
# FILL = 0
# MAX = 7
# '
# doesn't match '(?^​:STASH = 0x[[​:xdigit​:]]+\s+\"\\0\​:\​:\\x\{01\}\​:\​:\\x\{30cd\}\")'

# Failed test 'PROTOTYPE is escaped correctly'
# at t/Peek.t line 1338.
# 'SV = IV(0x1929ea0) at 0x1929ea4
# REFCNT = 1
# FLAGS = (ROK)
# RV = 0x194
# SV = PVCV(0x198f49c) at 0x194
# REFCNT = 2
# FLAGS = (POK,pPOK,DYNFILE,UTF8)
# PROTOTYPE = "\0\x{1}\x{30cd}"
# COMP_STASH = 0xdf6b54 "main"
# ROOT = 0x0
# GVGV​::GV = 0x194 "main" :​: "doof"
# FILE = "t/Peek.t"
# DEPTH = 0
# FLAGS = 0x1000
# OUTSIDE_SEQ = 0
# PADLIST = 0x0
# OUTSIDE = 0x0 (null)
# '
# doesn't match '(?^​:PROTOTYPE = \"\\0\\x\{01\}\\x\{30cd\}\")'
# Looks like you failed 2 tests of 112.
../ext/Devel-Peek/t/Peek.t .........................................
Dubious, test returned 2 (wstat 512, 0x200)
Failed 2/112 subtests
  (less 2 skipped subtests​: 108 okay)

--
Respectfully,
Dan Collins