porting/cpphdrcheck.t syntax errors std::nothrow on Mingw64 GCC 8.3.0 i386

[bulk88]

Description

t\porting\cpphdrcheck.t added in #22232 won't pass with mingw64 gcc 8.3.0, syntax error b/c of missing c++ header files (my guess) in the sample .cpp files it uses

STDOUT stream of t\porting\cpphdrcheck.t

# test run for g++
# probe g++ for standard C++11 with -std=c++11
# found 11 with -std=c++11
# probe g++ for standard C++14 with -std=c++14
# found 14 with -std=c++14
# probe g++ for standard C++17 with -std=c++17
# found 17 with -std=c++17
# probe g++ for standard C++20 with -std=c++20
# didn't find 20 with -std=c++20
# build: g++ -oa.out.exe  -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mms-bitfields -std=c++20 source.cpp 2>&1
# 
# build output: g++: error: unrecognized command line option '-std=c++20'; did you mean '-std=c++2a'?
# 
# build exit: 256
# probe g++ for standard C++23 with -std=c++23
# didn't find 23 with -std=c++23
# build: g++ -oa.out.exe  -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mms-bitfields -std=c++23 source.cpp 2>&1
# 
# build output: g++: error: unrecognized command line option '-std=c++23'; did you mean '-std=c++03'?
# 
# build exit: 256
ok 1 - test std base
# cmd: g++ -c  -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mms-bitfields -IC:\sources\perl5 -IC:\sources\perl5\lib\CORE source.cpp 2>&1
# out: 
not ok 2 - test std 11
not ok 3 - test std 14
not ok 4 - test std 17
1..4

trimmed piece of g++ --help=c++ from the binary

  -iwithprefixbefore <dir>    Add <dir> to the end of the main include path.
  -nostdinc                   Do not search standard system include directories
                              (those specified with -isystem will still be
                              used).
  -nostdinc++                 Do not search standard system include directories
                              for C++.
  -o <file>                   Place output into <file>.
  -pedantic                   Same as -Wpedantic.  Use the latter option
                              instead.
  -remap                      Remap file names when including files.
  -std=c++03                  Conform to the ISO 1998 C++ standard revised by
                              the 2003 technical corrigendum.  Same as
                              -std=c++98.
  -std=c++0x                  Deprecated in favor of -std=c++11.  Same as
                              -std=c++11.
  -std=c++11                  Conform to the ISO 2011 C++ standard.
  -std=c++14                  Conform to the ISO 2014 C++ standard.
  -std=c++17                  Conform to the ISO 2017 C++ standard.
  -std=c++1y                  Deprecated in favor of -std=c++14.  Same as
                              -std=c++14.
  -std=c++1z                  Deprecated in favor of -std=c++17.  Same as
                              -std=c++17.
  -std=c++2a                  Conform to the ISO 2020(?) C++ draft standard
                              (experimental and incomplete support).
  -std=c++98                  Conform to the ISO 1998 C++ standard revised by
                              the 2003 technical corrigendum.
  -std=gnu++03                Conform to the ISO 1998 C++ standard revised by
                              the 2003 technical corrigendum with GNU
                              extensions.  Same as -std=gnu++98.
  -std=gnu++0x                Deprecated in favor of -std=gnu++11.  Same as
                              -std=gnu++11.
  -std=gnu++11                Conform to the ISO 2011 C++ standard with GNU
                              extensions.
  -std=gnu++14                Conform to the ISO 2014 C++ standard with GNU
                              extensions.
  -std=gnu++17                Conform to the ISO 2017 C++ standard with GNU
                              extensions.
  -std=gnu++1y                Deprecated in favor of -std=gnu++14.  Same as
                              -std=gnu++14.
  -std=gnu++1z                Deprecated in favor of -std=gnu++17.  Same as
                              -std=gnu++17.
  -std=gnu++2a                Conform to the ISO 2020(?) C++ draft standard
                              with GNU extensions (experimental and incomplete
                              support).
  -std=gnu++98                Conform to the ISO 1998 C++ standard revised by
                              the 2003 technical corrigendum with GNU
                              extensions.
  -traditional-cpp            Enable traditional preprocessing.
  -trigraphs                  Support ISO C trigraphs.
  -undef                      Do not predefine system-specific and GCC-specific
                              macros.
  -v                          Enable verbose output.
  -w                          Suppress warnings.

C:\sources\perl5\win32>where g++
C:\Strawberry\c\bin\g++.exe

C:\sources\perl5\win32>g++ -dumpmachine
i686-w64-mingw32
C:\sources\perl5\win32>g++ -dumpversion
8.3.0
C:\sources\perl5\win32>g++ -v
Using built-in specs.
COLLECT_GCC=g++
COLLECT_LTO_WRAPPER=C:/Strawberry/c/bin/../libexec/gcc/i686-w64-mingw32/8.3.0/lt
o-wrapper.exe
Target: i686-w64-mingw32
Configured with: ../../../src/gcc-8.3.0/configure --host=i686-w64-mingw32 --buil
d=i686-w64-mingw32 --target=i686-w64-mingw32 --prefix=/mingw32 --enable-shared -
-enable-static --disable-multilib --enable-languages=c,c++,fortran,lto --enable-
libstdcxx-time=yes --enable-threads=posix --enable-libgomp --enable-libatomic --
enable-lto --enable-graphite --enable-checking=release --enable-fully-dynamic-st
ring --enable-version-specific-runtime-libs --enable-libstdcxx-filesystem-ts=yes
 --disable-sjlj-exceptions --with-dwarf2 --disable-libstdcxx-pch --disable-libst
dcxx-debug --disable-bootstrap --disable-rpath --disable-win32-registry --disabl
e-nls --disable-werror --disable-symvers --with-gnu-as --with-gnu-ld --with-arch
=i686 --with-tune=generic --with-libiconv --with-system-zlib --with-gmp=/opt/bui
ld/prerequisites/i686-w64-mingw32-static --with-mpfr=/opt/build/prerequisites/i6
86-w64-mingw32-static --with-mpc=/opt/build/prerequisites/i686-w64-mingw32-stati
c --with-isl=/opt/build/prerequisites/i686-w64-mingw32-static --with-pkgversion=
'i686-posix-dwarf, Built by strawberryperl.com project' --with-bugurl=https://so
urceforge.net/projects/mingw-w64 CFLAGS='-O2 -pipe -fno-ident -I/opt/build/i686-
830-posix-dwarf-rt_v6/mingw32/opt/include -I/opt/build/prerequisites/i686-zlib-s
tatic/include -I/opt/build/prerequisites/i686-w64-mingw32-static/include' CXXFLA
GS='-O2 -pipe -fno-ident -I/opt/build/i686-830-posix-dwarf-rt_v6/mingw32/opt/inc
lude -I/opt/build/prerequisites/i686-zlib-static/include -I/opt/build/prerequisi
tes/i686-w64-mingw32-static/include' CPPFLAGS=' -I/opt/build/i686-830-posix-dwar
f-rt_v6/mingw32/opt/include -I/opt/build/prerequisites/i686-zlib-static/include
-I/opt/build/prerequisites/i686-w64-mingw32-static/include' LDFLAGS='-pipe -fno-
ident -L/opt/build/i686-830-posix-dwarf-rt_v6/mingw32/opt/lib -L/opt/build/prere
quisites/i686-zlib-static/lib -L/opt/build/prerequisites/i686-w64-mingw32-static
/lib -Wl,--large-address-aware' LD_FOR_TARGET=/opt/build/i686-830-posix-dwarf-rt
_v6/mingw32/bin/ld.exe
Thread model: posix
gcc version 8.3.0 (i686-posix-dwarf, Built by strawberryperl.com project)
C:\sources\perl5\win32>

The GCC 8.3.0 binary+SDK being used isthe one bundled with Strawberry 5.32.1. Below is the -V of the bundled perl it came with, but this

C:\sources\perl5\win32>perl -V
Summary of my perl5 (revision 5 version 32 subversion 1) configuration:

  Platform:
    osname=MSWin32
    osvers=10.0.19042.746
    archname=MSWin32-x86-multi-thread-64int
    uname='Win32 strawberry-perl 5.32.1.1 #1 Sun Jan 24 12:17:47 2021 i386'
    config_args='undef'
    hint=recommended
    useposix=true
    d_sigaction=undef
    useithreads=define
    usemultiplicity=define
    use64bitint=define
    use64bitall=undef
    uselongdouble=undef
    usemymalloc=n
    default_inc_excludes_dot=define
    bincompat5005=undef
  Compiler:
    cc='gcc'
    ccflags =' -DWIN32 -D__USE_MINGW_ANSI_STDIO -DPERL_TEXTMODE_SCRIPTS -DPERL_I
MPLICIT_CONTEXT -DPERL_IMPLICIT_SYS -DUSE_PERLIO -fwrapv -fno-strict-aliasing -m
ms-bitfields'
    optimize='-s -O2'
    cppflags='-DWIN32'
    ccversion=''
    gccversion='8.3.0'
    gccosandvers=''
    intsize=4
    longsize=4
    ptrsize=4
    doublesize=8
    byteorder=12345678
    doublekind=3
    d_longlong=define
    longlongsize=8
    d_longdbl=define
    longdblsize=12
    longdblkind=3
    ivtype='long long'
    ivsize=8
    nvtype='double'
    nvsize=8
    Off_t='long long'
    lseeksize=8
    alignbytes=8
    prototype=define
  Linker and Libraries:
    ld='g++'
    ldflags ='-s -L"C:\STRAWB~1\perl\lib\CORE" -L"C:\STRAWB~1\c\lib"'
    libpth=C:\STRAWB~1\c\lib C:\STRAWB~1\c\i686-w64-mingw32\lib C:\STRAWB~1\c\li
b\gcc\i686-w64-mingw32\8.3.0
    libs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi3
2 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversio
n -lodbc32 -lodbccp32 -lcomctl32
    perllibs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladv
api32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lve
rsion -lodbc32 -lodbccp32 -lcomctl32
    libc=
    so=dll
    useshrplib=true
    libperl=libperl532.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs
    dlext=xs.dll
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags='-mdll -s -L"C:\STRAWB~1\perl\lib\CORE" -L"C:\STRAWB~1\c\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_IMPLICIT_CONTEXT
    PERL_IMPLICIT_SYS
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    USE_64_BIT_INT
    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 Jan 24 2021 12:22:49
  %ENV:
    PERL_JSON_BACKEND="Cpanel::JSON::XS"
    PERL_YAML_BACKEND="YAML::XS"
  @INC:
    C:/Strawberry/perl/site/lib
    C:/Strawberry/perl/vendor/lib
    C:/Strawberry/perl/lib
C:\sources\perl5\win32>

Steps to Reproduce

This probably isn't 100% identical to what is in cpphdrcheck.t but shows it has nothing to do perl API in C++ code but something in the non-perl C API related cmd line args cpphdrcheck.t given to g++ or missing #defines, or broken CC detection logic in cpphdrcheck.t.

This file fails

#include <new> // line not inside  `cpphdrcheck.t`  I added it but still failed same errors
#include <iostream>
#include <memory>

//#include "EXTERN.h" // disabled to reduce things going wrong
//#include "perl.h"
//#include "XSUB.h"



struct A {
    virtual const char *ok() { return "NOT OK\n"; };
    // = default C++11
    virtual ~A() = default;
};

struct B : A {
    // override C++11
    const char *ok() override { return "OK\n"; };
};

// unique ptr is C++11
std::unique_ptr<A> f() {
    return std::unique_ptr<A>{new B};
}

int main() {
  // auto as a placeholder type is C++11
  auto p = f();
  std::cout << p->ok();
  return 0;
}

when compiled by hand with

g++ -c  -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mms-bitfields -IC:\sources\perl5 -IC:\sources\perl5\lib\CORE -std=c++17 source2.cpp 

console log of failed .cpp sample

In file included from C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++
/memory:66,
                 from source2.cpp:3:
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/stl_tempbuf.h: I
n function 'std::pair<_Tp*, int> std::get_temporary_buffer(std::ptrdiff_t)':
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/stl_tempbuf.h:95
:13: error: 'nothrow' is not a member of 'std'
        std::nothrow));
             ^~~~~~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/stl_tempbuf.h: I
n function 'void std::return_temporary_buffer(_Tp*)':
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/stl_tempbuf.h:11
3:35: error: 'nothrow' is not a member of 'std'
     { ::operator delete(__p, std::nothrow); }
                                   ^~~~~~~
In file included from C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++
/bits/shared_ptr.h:52,
                 from C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++
/memory:81,
                 from source2.cpp:3:
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h: At global scope:
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h:723:61: error: 'std::nothrow_t' has not been declared
       explicit __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t);
                                                             ^~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h:905:50: error: 'std::nothrow_t' has not been declared
     __shared_count(const __weak_count<_Lp>& __r, std::nothrow_t)
                                                  ^~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h:1352:53: error: 'std::nothrow_t' has not been declared
       __shared_ptr(const __weak_ptr<_Tp, _Lp>& __r, std::nothrow_t)
                                                     ^~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h: In constructor 'std::__shared_ptr<_Tp, _Lp>::__shared_ptr(const std::__weak_p
tr<_Tp, _Lp>&, int)':
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h:1353:43: error: 'nothrow' is not a member of 'std'
       : _M_refcount(__r._M_refcount, std::nothrow)
                                           ^~~~~~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h: In member function 'std::__shared_ptr<_Tp, _Lp> std::__weak_ptr<_Tp, _Lp>::lo
ck() const':
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr_base.
h:1687:60: error: 'nothrow' is not a member of 'std'
       { return __shared_ptr<element_type, _Lp>(*this, std::nothrow); }
                                                            ^~~~~~~
In file included from C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++
/memory:81,
                 from source2.cpp:3:
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h: At
 global scope:
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h:367
:44: error: 'std::nothrow_t' has not been declared
       shared_ptr(const weak_ptr<_Tp>& __r, std::nothrow_t)
                                            ^~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h: In
 constructor 'std::shared_ptr<_Tp>::shared_ptr(const std::weak_ptr<_Tp>&, int)':

C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h:368
:37: error: 'nothrow' is not a member of 'std'
       : __shared_ptr<_Tp>(__r, std::nothrow) { }
                                     ^~~~~~~
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h: In
 member function 'std::shared_ptr<_Tp> std::weak_ptr<_Tp>::lock() const':
C:/Strawberry/c/lib/gcc/i686-w64-mingw32/8.3.0/include/c++/bits/shared_ptr.h:599
:44: error: 'nothrow' is not a member of 'std'
       { return shared_ptr<_Tp>(*this, std::nothrow); }
                                            ^~~~~~~

but if I change (the right word is add since next line not in the ,t)
#include <new>
to
#include <c++/new>
no more errors, console is silent, and I have a source2.o file on my disk.

C:\sources\perl5\win32>cd ..\t & g++ -c  -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTI
PLICITY -DPERL_IMPLICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-s
trict-aliasing -mms-bitfields -IC:\sources\perl5 -IC:\sources\perl5\lib\CORE -st
d=c++17 source2.cpp & cd ..\win32

C:\sources\perl5\win32>dir ..\t\source2.o
 Volume in drive C has no label.
 Volume Serial Number is C43E-2B1E

 Directory of C:\sources\perl5\t

08/20/2025  05:01 PM            23,187 source2.o
               1 File(s)         23,187 bytes
               0 Dir(s)  209,645,223,936 bytes free

C:\sources\perl5\win32>

IDK why adding
#include <c++/new>
before

#include <iostream>
#include <memory>

made it work.

Putting in #include <c++/new> and #include <new> were random ideas found and played around with by grepping GCC's headers. IDK y they worked, and I have no comment if adding #include <c++/new> is a correct fix or not. C++ isn't my specialty.

Expected behavior

A GCC released in Feb 2019 is still supported by p5p.

Perl configuration

C:\sources\perl5\win32>..\perl -I..\lib -V
Summary of my perl5 (revision 5 version 43 subversion 2) configuration:
  Derived from: ab823bcb5a9b91d0a9109770da317bde4f6c2db5
  Platform:
    osname=MSWin32
    osvers=6.1.7601
    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
    default_inc_excludes_dot=define
  Compiler:
    cc='gcc'
    ccflags ='-std=c99 -DWIN32 -DPERL_TEXTMODE_SCRIPTS -DMULTIPLICITY -DPERL_IMP
LICIT_SYS -DUSE_PERLIO -D__USE_MINGW_ANSI_STDIO -fwrapv -fno-strict-aliasing -mm
s-bitfields'
    optimize='-Os'
    cppflags='-DWIN32'
    ccversion=''
    gccversion='8.3.0'
    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:\Strawberry\c\lib" -L"C:\Strawberry\c
\i686-w64-mingw32\lib" -L"C:\Strawberry\c\lib\gcc\i686-w64-mingw32\8.3.0"'
    libpth=C:\Strawberry\c\lib C:\Strawberry\c\i686-w64-mingw32\lib C:\Strawberr
y\c\lib\gcc\i686-w64-mingw32\8.3.0
    libs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladvapi3
2 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lversio
n -lodbc32 -lodbccp32 -lcomctl32
    perllibs= -lmoldname -lkernel32 -luser32 -lgdi32 -lwinspool -lcomdlg32 -ladv
api32 -lshell32 -lole32 -loleaut32 -lnetapi32 -luuid -lws2_32 -lmpr -lwinmm -lve
rsion -lodbc32 -lodbccp32 -lcomctl32
    libc=-lmsvcrt
    so=dll
    useshrplib=true
    libperl=libperl543.a
    gnulibc_version=''
  Dynamic Linking:
    dlsrc=dl_win32.xs
    dlext=dll
    d_dlsymun=undef
    ccdlflags=' '
    cccdlflags=' '
    lddlflags='-shared -s -L"c:\perl\lib\CORE" -L"C:\Strawberry\c\lib" -L"C:\Str
awberry\c\i686-w64-mingw32\lib" -L"C:\Strawberry\c\lib\gcc\i686-w64-mingw32\8.3.
0"'


Characteristics of this binary (from libperl):
  Compile-time options:
    HAS_LONG_DOUBLE
    HAS_TIMES
    HAVE_INTERP_INTERN
    MULTIPLICITY
    PERLIO_LAYERS
    PERL_COPY_ON_WRITE
    PERL_DONT_CREATE_GVSV
    PERL_HASH_FUNC_ZAPHOD32
    PERL_HASH_USE_SBOX32
    PERL_IMPLICIT_SYS
    PERL_MALLOC_WRAP
    PERL_OP_PARENT
    PERL_PRESERVE_IVUV
    PERL_USE_SAFE_PUTENV
    USE_ITHREADS
    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 MSWin32
  Compiled at Aug 20 2025 12:24:41
  %ENV:
    PERL_JSON_BACKEND="Cpanel::JSON::XS"
    PERL_YAML_BACKEND="YAML::XS"
  @INC:
    ..\lib
    C:/sources/perl5/lib

C:\sources\perl5\win32>

[tonycoz]

Works for me (below).

I'm surprised you're getting to the point of testing against the headers if the code fails to compile with the headers commented out.

The compiler probe code first tries to compile the code with the //PERLHEADERS not replaced and should only try to test against that version and with the headers replaced if the original code compiled and ran successfully.

This was done because Sun C on Oracle Linux (IIRC) failed to build the C++ 11 sample without the perl headers.

C:\Users\Tony\dev\perl\git\perl\win32>perl -V
Summary of my perl5 (revision 5 version 32 subversion 1) configuration:

  Platform:
    osname=MSWin32
    osvers=10.0.19042.746
    archname=MSWin32-x86-multi-thread-64int
    uname='Win32 strawberry-perl 5.32.1.1 #1 Sun Jan 24 12:17:47 2021 i386'
    config_args='undef'
...
C:\Users\Tony\dev\perl\git\perl\win32>gmake -j3 CCHOME=c:\strawberry-perl-5.32.1.1-32bit-portable\c WIN64=undef test-prep
...
C:\Users\Tony\dev\perl\git\perl\win32>gmake -j3 CCHOME=c:\strawberry-perl-5.32.1.1-32bit-portable\c WIN64=undef test TEST_FILES=porting/cpphdrcheck.t
...
gmake[1]: Leaving directory 'C:/Users/Tony/dev/perl/git/perl/dist/threads-shared'
..\perl.exe -f ..\pod\buildtoc -q
xcopy /f /r /i /d /y ..\perl.exe ..\t\
0 File(s) copied
xcopy /f /r /i /d /y ..\perl543.dll ..\t\
0 File(s) copied
xcopy /f /r /i /d /y ..\perlglob.exe ..\t\
0 File(s) copied
set PERL_STATIC_EXT=Win32CORE && \
    cd ..\t && perl.exe harness   porting/cpphdrcheck.t
porting/cpphdrcheck.t .. ok
All tests successful.
Files=1, Tests=4, 10 wallclock secs ( 0.03 usr +  0.00 sys =  0.03 CPU)
Result: PASS
Finished test run at Thu Aug 21 15:06:00 2025.

C:\Users\Tony\dev\perl\git\perl\win32>g++ -dumpmachine
i686-w64-mingw32

C:\Users\Tony\dev\perl\git\perl\win32>where g++
c:\strawberry-perl-5.32.1.1-32bit-portable\c\bin\g++.exe

[tonycoz]

I wonder if you're picking up a header from a different install somewhere, perhaps:

g++ -xc++ nul -E -Wp,-v

would be enlightening, it picked up a search directory I added to CPLUS_INCLUDE_PATH, as well as the default paths.