leveldb @1.19_0 - links against libstdc++ on 10.6 with libcxx, preventing function. And workaround.

[kencu (Ken)]

leveldb installs, but fails to link correctly when used, on 10.6 with libc++ (and I imagine other similar systems <10.9 upgraded to libc++).

$ otool -L /opt/local/lib/libleveldb.dylib
/opt/local/lib/libleveldb.dylib:
	/opt/local/lib/libleveldb.1.dylib (compatibility version 0.0.0, current version 0.0.0)
	/opt/local/lib/libsnappy.1.dylib (compatibility version 5.0.0, current version 5.0.0)
	/usr/lib/libstdc++.6.dylib (compatibility version 7.0.0, current version 7.9.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.11)

this resulted in a link error in the port that was using leveldb:

Undefined symbols for architecture x86_64:
  "leveldb::DB::Open(leveldb::Options const&, std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&, leveldb::DB**)", referenced from:
      Database_LevelDB::Database_LevelDB(std::__1::basic_string<char, std::__1::char_traits<char>, std::__1::allocator<char> > const&) in database-leveldb.cpp.o
ld: symbol(s) not found for architecture x86_64

the leveldb portfile shows some shenanigans were done due to troubles finding the Snappy library.

Adding the following references to libc++ into the portfile and building it +universal did work:

if { [variant_isset universal] } {
    foreach arch ${configure.universal_archs} {
        set merger_build_env(${arch}) "CFLAGS=\"-arch ${arch}\" CXXFLAGS=\"-arch ${arch} -stdlib=libc++\"  LDFLAGS=\"-arch ${arch} -stdlib=libc++ -L${prefix}/lib\""
    }

and generated a proper binary

$ otool -L /opt/local/lib/libleveldb.dylib
/opt/local/lib/libleveldb.dylib:
	/opt/local/lib/libleveldb.1.dylib (compatibility version 0.0.0, current version 0.0.0)
	/opt/local/lib/libsnappy.1.dylib (compatibility version 5.0.0, current version 5.0.0)
	/usr/lib/libc++.1.dylib (compatibility version 1.0.0, current version 3.9.0)
	/usr/lib/libSystem.B.dylib (compatibility version 1.0.0, current version 125.2.11)
	/usr/lib/libc++abi.dylib (compatibility version 1.0.0, current version 3.9.0)

which in the end linked correctly with the final port that needed it.

Although this works, it's clearly a bit of a hack -- no doubt the proper way to the fix this issue will be obvious to someone.

[ryandesign (Ryan Carsten Schmidt)]

In e7838648d8264c2dc1d8f2881985d57915167051/macports-ports:

leveldb: Update to 1.20

Add gperftools dependency.

Closes: #55584

Honor cxx_stdlib.

Closes: #53104