the version of the c-runtime would have more to do with NaN than perl version

which is why it surprised me that in the test matrix, same user on apparently the same system, with two different perl versions but same gcc version and same libc version, got different results.

apparently the same system, with two different perl versions but same gcc version and same libc version, got different results

Are you sure ?
It's no big deal but I'd be interested to see 2 reports indicative of that.

Cheers,
Rob

For me, on the same system, it passes on 5.22+, but fails on everything below that. I'm wondering if it may be related to Infinity and NaN (not-a-number) handling improved changes mentioned in perldelta-5.22.

I'd be interested to see 2 reports indicative of that.

The two reports linked in my original post: both showed linux 3.16.0-4-amd64 debian 3.16.7-ckt25-2 (2016-04-08) with gccversion='4.9.2', libc=libc-2.19.so, and gnulibc_version='2.19', the only difference being 5.20.1 vs 5.22.0. But as stevieb replied, it's probably the improved NaN handling in 5.22 which fixed the bug. (Which then surprises me that my ancient linux perl v5.8.5 passed... but then again, there were probably other NaN handling changes in Perl or differences between the systems/compilers).

excerpts from the fail reports in the spoiler

5.20 FAIL

Summary of my perl5 (revision 5 version 20 subversion 1) configuration
+:
   
  Platform:
    osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux
    uname='linux eserte 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt25-2 (2
+016-04-08) x86_64 gnulinux '
    config_args='-ds -e -Dprefix=/opt/perl-5.20.1 -Dcf_email=srezic@cp
+an.org'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-prot
+ector -I/usr/local/include -D_LARGEFILE_SOURCE -D_FILE_OFFSET_BITS=64
+',
    optimize='-O2',
    cppflags='-fwrapv -fno-strict-aliasing -pipe -fstack-protector -I/
+usr/local/include'
    ccversion='', gccversion='4.9.2', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+6
    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 -L/usr/local/lib'
    libpth=/usr/local/lib /usr/lib/gcc/x86_64-linux-gnu/4.9/include-fi
+xed /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
    libs=-lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdbm_compat
    perllibs=-lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.19'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstac
+k-protector'
[download]

5.22 PASS

Summary of my perl5 (revision 5 version 22 subversion 0) configuration
+:
   
  Platform:
    osname=linux, osvers=3.16.0-4-amd64, archname=x86_64-linux
    uname='linux eserte 3.16.0-4-amd64 #1 smp debian 3.16.7-ckt25-2 (2
+016-04-08) x86_64 gnulinux '
    config_args='-ds -e -Dprefix=/opt/perl-5.22.0 -Dcf_email=srezic@cp
+an.org'
    hint=recommended, useposix=true, d_sigaction=define
    useithreads=undef, usemultiplicity=undef
    use64bitint=define, use64bitall=define, uselongdouble=undef
    usemymalloc=n, bincompat5005=undef
  Compiler:
    cc='cc', ccflags ='-fwrapv -fno-strict-aliasing -pipe -fstack-prot
+ector-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-str
+ong -I/usr/local/include'
    ccversion='', gccversion='4.9.2', gccosandvers=''
    intsize=4, longsize=8, ptrsize=8, doublesize=8, byteorder=12345678
+, doublekind=3
    d_longlong=define, longlongsize=8, d_longdbl=define, longdblsize=1
+6, 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/4.9/include-fi
+xed /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
    libs=-lpthread -lnsl -lgdbm -ldb -ldl -lm -lcrypt -lutil -lc -lgdb
+m_compat
    perllibs=-lpthread -lnsl -ldl -lm -lcrypt -lutil -lc
    libc=libc-2.19.so, so=so, useshrplib=false, libperl=libperl.a
    gnulibc_version='2.19'
  Dynamic Linking:
    dlsrc=dl_dlopen.xs, dlext=so, d_dlsymun=undef, ccdlflags='-Wl,-E'
    cccdlflags='-fPIC', lddlflags='-shared -O2 -L/usr/local/lib -fstac
+k-protector-strong'
[download]