From @ilmari

Debian unstable with g++ 6.2.0 and glibc 2.24.
Works fine with g++ 5.4.1 and gcc 5.4.1 and 6.2.0.
Full build log attached.

t/op/sprintf2 ... # Failed test 1492 - subnormal 0x1.fffffffffffffp-1022 %a 0x1.fffffffffffffp-1022 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.fffffffffffffp-1022"
# Failed test 1493 - subnormal 0x0.fffffffffffffp-1022 %a 0x1.ffffffffffffep-1023 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.ffffffffffffep-1023"
# Failed test 1494 - subnormal 0x0.7ffffffffffffp-1022 %a 0x1.ffffffffffffcp-1024 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.ffffffffffffcp-1024"
# Failed test 1495 - subnormal 0x0.3ffffffffffffp-1022 %a 0x1.ffffffffffff8p-1025 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.ffffffffffff8p-1025"
# Failed test 1496 - subnormal 0x0.1ffffffffffffp-1022 %a 0x1.ffffffffffffp-1026 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.ffffffffffffp-1026"
# Failed test 1497 - subnormal 0x0.0ffffffffffffp-1022 %a 0x1.fffffffffffep-1027 got 0x0p+0 at op/sprintf2.t line 811
# got "0x0p+0"
# expected "0x1.fffffffffffep-1027"
FAILED at test 1492
Failed 1 test out of 0, 0.00% okay.
  op/sprintf2.t

$ ./perl -Ilib -V
Summary of my perl5 (revision 5 version 25 subversion 6) configuration​:
  Commit id​: 917aa34
  Platform​:
  osname=linux
  osvers=4.7.0-1-amd64
  archname=x86_64-linux
  uname='linux sid-usrsplit 4.7.0-1-amd64 #1 smp debian 4.7.6-1 (2016-10-07) x86_64 gnulinux '
  config_args='-des -Dusedevel -Uversiononly -Dcc=g++'
  hint=recommended
  useposix=true
  d_sigaction=define
  useithreads=undef
  usemultiplicity=undef
  use64bitint=define
  use64bitall=define
  uselongdouble=undef
  usemymalloc=n
  bincompat5005=undef
  Compiler​:
  cc='g++'
  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='6.2.0 20161010'
  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='g++'
  ldflags =' -fstack-protector-strong -L/usr/local/lib'
  libpth=/usr/include/c++/6 /usr/include/x86_64-linux-gnu/c++/6 /usr/include/c++/6/backward /usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/6/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 -lgdbm_compat
  perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
  libc=libc-2.24.so
  so=so
  useshrplib=false
  libperl=libperl.a
  gnulibc_version='2.24'
  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_HASH_FUNC_ONE_AT_A_TIME_HARD
  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
  Built under linux
  Compiled at Oct 17 2016 13​:36​:07
  @​INC​:
  lib
  /usr/local/lib/perl5/site_perl/5.25.6/x86_64-linux
  /usr/local/lib/perl5/site_perl/5.25.6
  /usr/local/lib/perl5/5.25.6/x86_64-linux
  /usr/local/lib/perl5/5.25.6
  .

From @ilmari

build.log

From @ilmari

--
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"Never formulate a law or axiom that you're not prepared to live with
the consequences of." -- Skud's Meta-Law

@khwilliamson - Status changed from 'new' to 'open'