bitcoin-qt FTBFS : undefined reference to symbol 'shm_unlink@@GLIBC_2.2.5'

[dooglus]

Since updating archlinux i've been unable to build bitcoin-qt from git HEAD.

The error is as follows:

$ make
g++ -m64 -Wl,-O1,--sort-common,--as-needed,-z,relro,--hash-style=gnu -fstack-protector -Wl,-O1 -o bitcoin-qt build/bitcoin.o [...] build/qrc_bitcoin.o -L/usr/lib -lqrencode -lminiupnpc -lssl -lcrypto -ldb_cxx -lboost_system -lboost_filesystem -lboost_program_options -lboost_thread -lQtGui -lQtCore -lpthread
/usr/bin/ld: build/qtipcserver.o: undefined reference to symbol 'shm_unlink@@GLIBC_2.2.5'
/usr/bin/ld: note: 'shm_unlink@@GLIBC_2.2.5' is defined in DSO /lib/librt.so.1 so try adding it to the linker command line
/lib/librt.so.1: could not read symbols: Invalid operation
collect2: ld returned 1 exit status
make: *** [bitcoin-qt] Error 1
$

I made the following change to bitcoin-qt.pro and the problem went away:

LIBS += $$join(BOOST_LIB_PATH,,-L,) $$join(BDB_LIB_PATH,,-L,) $$join(OPENSSL_LIB_PATH,,-L,) $$join(QRENCODE_LIB_PATH,,-L,)
-LIBS += -lssl -lcrypto -ldb_cxx$$BDB_LIB_SUFFIX
+LIBS += -lssl -lcrypto -ldb_cxx$$BDB_LIB_SUFFIX -lrt

-lgdi32 has to happen after -lcrypto (see #681)

I don't know enough about what's going on to say whether that's a good idea, but it worked for me...

[laanwj]

Adding -rt should be done only for Linux, I suppose? It's strange that we'd have to link against it directly, as we don't use shm_open/shm_unlink directly, it is at most Boost using it.

[dooglus]

When trying to understand the change I found a link:
http://fedoraproject.org/wiki/UnderstandingDSOLinkChange
that claims to explain it.

Hope that helps!

[dooglus]

The undefined symbol is referenced on line 374 of /usr/include/boost/interprocess/shared_memory_object.hpp,
included by /usr/include/boost/interprocess/ipc/message_queue.hpp,
included by bitcoin/src/qt/qtipcserver.cpp

[laanwj]

Yes, that makes it fully clear. We must link to -lrt on Linux, as previously we were using it indirectly through some other lib and that's no longer allowed...

[pio2398]

On Fedora You fix help too.

[bitaussie]

Is that some kind of a stack-based language?

Does changing "LIBS += -lssl -lcrypto -ldb_cxx$$BDB_LIB_SUFFIX" to "LIBS += -lssl -lcrypto -ldb_cxx$$BDB_LIB_SUFFIX -lrt" in bitcoin-qt.pro fix it on Fedora?

[laanwj]

Fixed now.