mpdecimal @4.0.0_1: Build failure on legacy OS X due to undefined symbols

[0xbf00 (Jakob)]

While trying to install python313 on an ancient Mac OS X 10.5 Leopard, the dependency mpdecimal fails to build.

According to the build logs, clang complains about undefined symbols, though checking the source code, these symbols should exist.

:info:build /opt/local/bin/clang++-mp-11 -pthread -L../libmpdec -dynamiclib -fPIC -install_name /opt/local/lib/libmpdec++.4.dylib -compatibility_version 4.0 -current_version 4.0.0 -o libmpdec++.4.0.0.dylib .objs/decimal.o -lmpdec -lm
:info:build Undefined symbols for architecture i386:
:info:build   "std::basic_ostream<char, std::char_traits<char> >& std::__ostream_insert<char, std::char_traits<char> >(std::basic_ostream<char, std::char_traits<char> >&, char const*, int)", referenced from:
:info:build       decimal::Context::repr() const in decimal.o
:info:build       decimal::operator<<(std::ostream&, decimal::Context const&) in decimal.o
:info:build       decimal::operator<<(std::ostream&, decimal::Decimal const&) in decimal.o
:info:build   "std::runtime_error::runtime_error(char const*)", referenced from:
:info:build       decimal::Context::raiseit(unsigned int) in decimal.o
:info:build       __ZN7decimal11MallocErrorCI1St13runtime_errorEPKc in decimal.o
:info:build       decimal::Context::repr() const in decimal.o
:info:build       decimal::Decimal::exact(char const*, decimal::Context&) in decimal.o
:info:build       __ZN7decimal10ValueErrorCI1St13runtime_errorEPKc in decimal.o
:info:build       decimal::Decimal::ln10(long long, decimal::Context&) in decimal.o

Maybe another case of system-supplied headers interfering with building?

[0xbf00 (Jakob)]

Build log (failing)

[Schamschula (Marius Schamschula)]

Snow Leopard had a clean build for i386. I have no way of checking this on Leopard (my only computer with Leopard is on another continent and doesn't have MacPorts installed). I'm currently building on Sonoma and Sequoia.

Input/PRs from those running older systems is always welcome!

[0xbf00 (Jakob)]

At least the second symbol std::runtime_error::runtime_error(char const*) is part of the standard C++ library. I can compile a toy example program using this symbol with the same compiler used to compile mpdecimal.

[kencu (Ken)]

possibly happening because -stdlib=macports-libstdc++ is not making it onto to the link line, despite being in the CXXFLAGS.

[ryandesign (Ryan Carsten Schmidt)]

Replying to Schamschula:

I have no way of checking this on Leopard

But you do have the ability on any system to verify whether the -stdlib flag is making it into the link command.

Replying to kencu:

possibly happening because -stdlib=macports-libstdc++ is not making it onto the link line, despite being in the CXXFLAGS.

Many build systems only use LDFLAGS (not CXXFLAGS) at link time. If that's the case here, options include patching the build system to add CXXFLAGS to the flags used at link time, or modifying the portfile to add the -stdlib flag to configure.ldflags such as:

if {[string match *clang* ${configure.cxx}] && ${configure.cxx_stdlib} ne ""} {
    configure.ldflags-append -stdlib=${configure.cxx_stdlib}
}

[Schamschula (Marius Schamschula)]

./configure --help for mpdecimal has separate linker flags:

LDXX        C++ linker (default is $CXX)
LDXXFLAGS   C++ linker flags

[kencu (Ken)]

Replying to ryandesign:

Many build systems only use LDFLAGS (not CXXFLAGS) at link time.

Some might, but it's just wrong if they do.

The link line for a CXX link should look like this:

$(CXX) $(CXXFLAGS) $(LDFLAGS) -o $(appname) $(objects) $(LDLIBS)

[kencu (Ken)]

this works on 10.5 Intel:

# https://trac.macports.org/ticket/71164
configure.args-append LDXXFLAGS=\"${configure.cxxflags}\"

[kencu (Ken)]

In e02a27ea2805e305da01cf3ee8c18fb0474da61f/macports-ports (master):

mpdecimal: use CXXFLAGS during link

closes: #71164