gnu global don't work properly with erlang

[lhbaccount]

Environment:

OS: Linux version 4.10.0-42-generic (address@hidden) (gcc 
version 5.4.0 20160609 (Ubuntu 5.4.0-6ubuntu1~16.04.5) ) 
#46~16.04.1-Ubuntu SMP Mon Dec 4 15:57:59 UTC 2017

Global: global (GNU GLOBAL) 6.6

I also installed universal-ctags in /usr/local and

        export GTAGSCONF=/usr/local/share/gtags/gtags.conf
        export GTAGSLABEL=builtin-first

add 2 line to /usr/local/share/gtags/gtags.conf

builtin-first:\
        :tc=native:tc=new-ctags:


---------------------
Command executed

address@hidden:~/src/rabbitmq-server-v3_6_6$ gtags

ctags: Warning: Unknown language 	 
"c:.c.h,yacc:.y,asm:.s.S,java:.java,c++:.c++.cc.hh.cpp.cxx.hxx.hpp.C.H,php:.php.php3.phtml,Ada:.adb.ads.Ada,Ant:(build.xml)(*.build.xml).ant.xml,Asm:.A51(*.29[kK])(*.[68][68][kKsSxX])(*.[xX][68][68]).asm.ASM,Asp:.asp.asa,Autoconf:(configure.in).ac,Automake:(Makefile.am).am,Awk:.awk.gawk.mawk,Basic:.bas.bi.bb.pb,BETA:.bet,Clojure:.clj.cljs.cljc,C++:.cp.h++.hp.inl,CSS:.css,C#:.cs,ctags:.ctags,Cobol:.cbl.cob.CBL.COB,CUDA:.cu.cuh,D:.d.di,Diff:.diff.patch,DTD:.dtd.mod,DTS:.dts.dtsi,DosBatch:.bat.cmd,Eiffel:.e,elm:.elm,Erlang:.erl.ERL.hrl.HRL,Falcon:.fal.ftd,Flex:.as.mxml,Fortran:.f.for.ftn.f77.f90.f95.f03.f08.f15,gdbinit:(.gdbinit).gdb,Go:.go,HTML:.htm.html,Iniconf:.ini.conf,ITcl:.itcl,JavaProperties:.properties,JavaScript:.js.jsx,JSON:.json,LdScript:(*.lds.S)(ld.*).lds.scr.ld,Lisp:.cl.clisp.el.l.lisp.lsp,Lua:.lua,M4:.m4.spt,man:.1.2.3.4.5.6.7.8.9,Make:([Mm]akefile)(GNUmakefile).mak.mk,MatLab:.m,Myrddin:.myr,ObjectiveC:.mm,OCaml:.ml.mli.aug,passwd:(passwd),Pascal:.p.pas,Perl:.pl.pm.ph.plx.perl,Perl6:.p6.pm6.pl6,PHP:.php4.php5.php7,pod:.pod,Protobuf:.proto,puppetManifest:.pp,Python:.py.pyx.pxd.pxi.scons,QemuHX:.hx,R:.r.R.q,REXX:.rexx.rx,Robot:.robot,RpmSpec:.spec,reStructuredText:.rest.reST.rst,Ruby:.rb.ruby,Rust:.rs,Scheme:.SCM.SM.sch.scheme.scm.sm,Sh:.sh.SH.bsh.bash.ksh.zsh.ash,SLang:.sl,SML:.sml.sig,SQL:.sql,SystemdUnit:.unit.service.socket.device.mount.automount.swap.target.path.timer.snapshot.scope.slice.time,Tcl:.tcl.tk.wish.exp,Tex:.tex,TTCN:.ttcn.ttcn3,Vera:.vr.vri.vrh,Verilog:.v,SystemVerilog:.sv.svh.svi,VHDL:.vhdl.vhd,Vim:(vimrc)([._]vimrc)(gvimrc)([._]gvimrc).vim.vba,WindRes:.rc,YumRepo:.repo,Zephir:.zep,Glade:.glade,Maven2:(pom.xml).pom,PlistXML:.plist,RelaxNG:.rng,SVG:.svg,XSLT:.xsl.xslt" 
in "langmap" option

address@hidden:~/src/rabbitmq-server-v3_6_6$ ls  -l G*

-rw-r--r-- 1 lisp lisp  49152 12月 14 15:40 GPATH
-rw-r--r-- 1 lisp lisp  16384 12月 14 15:40 GRTAGS
-rw-r--r-- 1 lisp lisp 827392 12月 14 15:40 GTAGS

When I execute gtags in a erlang project, ctags report a warning, but 
the G-files still generated. The problem is: global can find definition, 
but not reference. "global -r" always print nothing. The GRTAGS file is 
also very small compared to GTAGS and GPATH.

When I execute gtags in a java project, it works correctly.