Re: Link fails on Ubuntu 16.04 (on WSL) due to undefined reference to symbol 'FcUcs4ToUtf8'

[sfeam <sf...@us...>]

On Sunday, 11 March 2018 14:04:19 Tatsuro MATSUOKA wrote:
> Sorry I forgot to reply to beta-list
> 
> ----- Original Message -----
> 
> > From: Dima Kogan
> > To: gnuplot-beta
> > Cc: 
> > Date: 2018/3/11, Sun 10:55
> > Subject: Re: Link fails on Ubuntu 16.04 (on WSL) due to undefined reference to symbol 'FcUcs4ToUtf8'
> > 
> >T atsuro MATSUOKA <tma...@ya...> writes:
> > 
> >>  I pull the recent git repository and tried to build on Ubuntu 16.04 on
> >>  WSL.
> >> 
> >>  In linking gnuplot executable I see
> >> 
> >>  undefined reference to symbol 'FcUcs4ToUtf8'
> > 
> > You're either not linking with the libfontconfig library, or you have
> > the wrong library, or something. Send over the full build log if you
> > want help debugging.
> > 
> > ------------------------------------------------------------------------------
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> 
> 
> You are right. In link stage, -lfontconfig is missing.
> 
> c++ 
>  -g -O2 -I/usr/lib/x86_64-linux-gnu/wx/include/gtk2-unicode-3.0 
> -I/usr/include/wx-3.0 -D_FILE_OFFSET_BITS=64 -DWXUSINGDLL -D__WXGTK__ 
> -pthread -I/opt/fontconfig-2.12.93/include -I/usr/include/pango-1.0 
> -I/usr/include/harfbuzz -I/usr/include/pango-1.0 -I/usr/include/cairo 
> -I/usr/include/glib-2.0 -I/usr/lib/x86_64-linux-gnu/glib-2.0/include 
> -I/usr/include/pixman-1 -I/usr/include/uuid -I/usr/include/freetype2 
> -I/usr/include/libpng12 -DWXT_MONOTHREADED -fPIC   -lcerf  -o gnuplot 
> alloc.o axis.o breaders.o boundary.o color.o command.o contour.o 
> datablock.o datafile.o dynarray.o eval.o external.o fit.o gadgets.o 
> getcolor.o graph3d.o graphics.o help.o hidden3d.o history.o internal.o 
> interpol.o jitter.o libcerf.o matrix.o misc.o mouse.o multiplot.o 
> parse.o plot.o plot2d.o plot3d.o pm3d.o readline.o save.o scanner.o 
> set.o show.o specfun.o standard.o stats.o stdfn.o tables.o tabulate.o 
> term.o time.o unset.o util.o util3d.o variable.o version.o
> wxterminal/wxt_gui.o wxterminal/gp_cairo.o 
> wxterminal/gp_cairo_helpers.o  qtterminal/qt_term.o -lreadline  
> -lncurses  -lz -lgd -lgd -llua5.3 -lcaca  -L/usr/lib/x86_64-linux-gnu 
> -pthread   -lwx_gtk2u_xrc-3.0 -lwx_gtk2u_html-3.0 -lwx_gtk2u_qa-3.0 
> -lwx_gtk2u_adv-3.0 -lwx_gtk2u_core-3.0 -lwx_baseu_xml-3.0 
> -lwx_baseu_net-3.0 -lwx_baseu-3.0  -lpangocairo-1.0 -lpango-1.0 
> -lgobject-2.0 -lglib-2.0 -lcairo  -lX11  -lQt5Network -lQt5Svg 
> -lQt5PrintSupport -lQt5Widgets -lQt5Gui -lQt5Core -lcaca -ldl -lm 
> -lcerf  -lz -lpangocairo-1.0 -lpango-1.0 -lgobject-2.0 -lcairo 
> -lglib-2.0
> 
> Adding manually -lfontcondig to the above, link is successful.
> 
> Compressed config.log.bz2 is attached.
> 
> Workaround is to add LIBS='-lfontconfig' to configure flag.


I do not understand why the configure script is not doing that
already.  It tests for the library using this command:

  AC_SEARCH_LIBS(foo, fontconfig, ,
  AC_DEFINE(HAVE_LIBFONTCONFIG,1,[ used for unicode codepoint->utf8 conversion ]),,)

The documentation for AC_SEARCH_LIBS says that it will

  Search for a library defining function if it's not already available.
  [...]
  Prepend -llibrary to LIBS for the first library found to contain function,
  and run action-if-found. If the function is not found, run action-if-not-found.

It must have found the function (since your code is trying to use it
inside a conditional for HAVE_LIBFONTCONFIG), so it should have added
-lfontconfig to the definition of LIBS.   Why did it not?

But also I do not understand for a second reason.
As you say, libfontconfig is already used by various support libraries
that gnuplot already uses  (cairo pango-ft gdlib qt ...).
So it must surely be linked in already because of the library dependencies
for various terminals.  I wonder that is not true on your machine.

When I run ./configure it adds -lfontconfig to both TERM_LIBS
and GTK_LIBS.  Does this not happen on your setup?

I am not very good at using or modifying the autoconf tools.
I hope someone else can help explain or fix this.

	Ethan

 

> 
> 
> I think that gnuplot so far uses fontconfig via external libraries (e.g. cairo, pango).
> Is this Commit [7ecbe3] first event to use fontconfig directory.
> Gnuplot check libfontconfig add -lfontconfig in library flag.
> 
> Tatsuro
> 
> 
> If it is in the case, libconfig
> 
> Tatsuro