nmap compilation fails

[lemzwerg (Werner Lemberg)]

[macOS 10.7.5 11G63]
[Xcode 4.6.3 4H1503]
[macports-ports commit f939548d4]
[cxx_stdlib libc++]

Compilation/linking of nmap fails on my Mac with undefined symbols, see attached log file.

[lemzwerg (Werner Lemberg)]

Log file of failing nmap build

[danielluke (Daniel J. Luke)]

I don't have a 10.7 system to test on, and am no inclined to spend time trying to make builds work on OS releases that are no longer receiving security patches from the OS vendor.

Having said that, I'm happy to review and include any patches to the port that you can generate to fix the build on your system. Feel free to re-open this ticket with a patch (or open a Pull Request).

[kencu (Ken)]

Here is the issue:

:info:build /usr/bin/clang++ -L/opt/local/lib -Wl,-headerpad_max_install_names -arch x86_64 -L/opt/local/lib -Lnbase -Lnsock/src/   -o nmap charpool.o FingerPrintResults.o FPEngine.o FPModel.o idle_scan.o MACLookup.o nmap_dns.o nmap_error.o nmap.o nmap_ftp.o NmapOps.o NmapOutputTable.o nmap_tty.o osscan2.o osscan.o output.o payload.o portlist.o portreasons.o protocols.o scan_engine.o scan_engine_connect.o scan_engine_raw.o scan_lists.o service_scan.o services.o NewTargets.o TargetGroup.o Target.o targets.o tcpip.o timing.o traceroute.o utils.o xml.o nse_main.o nse_utility.o nse_nsock.o nse_dnet.o nse_fs.o nse_nmaplib.o nse_debug.o nse_pcrelib.o nse_lpeg.o nse_openssl.o nse_ssl_cert.o nse_libssh2.o nse_zlib.o main.o -lnsock -lnbase -lpcre -lpcap libssh2/lib/libssh2.a -lssl -lcrypto -lz libnetutil/libnetutil.a ./libdnet-stripped/src/.libs/libdnet.a ./liblua/liblua.a ./liblinear/liblinear.a -lm 
:info:build Undefined symbols for architecture x86_64:
:info:build   "std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> >::find_first_of(char const*, unsigned long, unsigned long) const", referenced from:
:info:build       __ZL15filename_to_urlPKc in NmapOps.o

when nmap builds and links, it does not specify a stdlib setting on the build line. By default, clang on systems < 10.9 examines the build and link lines for a -stdlib setting, and if none is found, clang defaults to adding -stdlib=libstdc++. That causes the build to fail because it does not find all the proper symbols that it is looking for, as noted by the std::__1:* errors.

The proper fix is to force the stdlib onto the build and link lines. However, this is a bit of a PITA.

Another fix is to make clang default to adding -stdlib=libc++ on your libc++ system which is configured that way. This matches the behaviour of all the newer systems, 10.9 and newer.

I changed clang-5.0 and newer to do exactly that on systems configured to used libc++ in their macports.conf, like yours. It can be seen by the default variants for clang-5.0, which, on your system, should be clang-5.0 +analyzer +defaultlibcxx +libstdcxx.

The +defaultlibcxx variant makes clang-5.0 add -stdlib=libc++ if none is specified, rather than -stdlib=libstdc++, which is what you want it to do on your system.

SHORT story. If your clang-5.0 is installed correctly, with the +defaultlibcxx variant on your system, building nmap with clang-5.0 should work correctly, ie do this:

sudo port clean nmap
sudo port -v install nmap configure.compiler=macports-clang-5.0

To add the -stdlib to the build line instead, you would need to dig in a bit to the build. botan does a fix for this, with a patch and then a reinplace:

# respect MacPorts configure values
patchfiles-append   patch-compiler_flags.diff \
                    patch-fix-install-with-destdir.diff \
                    patch-python_exe.diff \
                    patch-map_anon.diff

post-patch {
    reinplace -W ${worksrcpath}/src/build-data/cc \
        "s|__MACPORTS_CXX_STDLIB__|${configure.cxx_stdlib}|g" \
        clang.txt
}

alternatively, sometimes you can just add it to the build line by adding a configure.cxxflags-append -- caution though, -stdlib=XYZ is only supported by clang, so you have to test to make sure that the build compiler is clang if you do this.

[lemzwerg (Werner Lemberg)]

Ken, thanks a lot for this very helpful answer! Using

sudo port -v install nmap configure.compiler=macports-clang-5.0

worked like a charm. Would it be possible to add this to the Portfile in a clean way?

[kencu (Ken)]

This is where we are running into some resistance/differences of opinion on MacPorts. There are those who will want only the ideal "build fix" solution used, and no other fix is acceptable -- then this ticket sits for months or years, as nobody will usually bother to spend the time to fix it like that on an old, unsupported system.

You could blacklist all compilers prior to clang-5.0 on systems < 10.9 that are configured to use libcxx. That would work, and the logic flows smoothly enough. It is also kinda ugly in the Portfile. You see what I mean. When I do propose these kinds of fixes, the PRs tend to sit in the PR queue for weeks and go nowhere until I just close them out of frustration.

Sooner or later we'll default to libcxx on all Intel systems 10.5+ -- then this will be easier to fix cleanly for everyone in base, because we'll just build with clang-5.0 and newer by default always.

In the meantime, I have set my "default compiler" in macports.conf to be clang-5.0, and that just fixes all these builds with ease. I suggest you consider doing that too.

[lemzwerg (Werner Lemberg)]

Thanks for the advice. However, how do I set up the default compiler in macports.conf? The documentation at ​https://guide.macports.org/chunked/internals.configuration-files.html doesn't give a hint, as far as I can see.

[kencu (Ken)]

add this

default_compilers macports-clang-5.0

[lemzwerg (Werner Lemberg)]

Thanks!

[kencu (Ken)]

See also <​https://github.com/nmap/nmap/issues/1161>

[kencu (Ken)]

In ed5913a3ac2c2f99f8e2e826c3eab80f08832d17/macports-ports (master):

nmap: add stdlib to LDFLAGS

fixes build with some build configurations
see #58837
see #53995