Re: 5.2 rc2 tarball now available

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

On Thursday, 06 July 2017 12:38:13 Daniel J Sebald wrote:
> On 07/05/2017 05:08 PM, Petr Mikulik wrote:
> >>>>>> I have troubles compiling rc2 on Linux (OpenSUSE 42.2, and some
> >>>>>> Ubuntu) linking fails.
> >>>>>>
> >>>>>> It is this problem:
> >>>>>>      https://sourceforge.net/p/gnuplot/support-requests/196/
> >>>>>>
> >>>>>> The workaround
> >>>>>>      configure --with-X11
> >>>>>> described above does not help, while
> >>>>>>      TERMLIBS="-lX11" ./configure
> >>>>>> let me gnuplot compile.
> >>>>>>
> >>>>>> Can this be fixed?
> >>>>>
> >>>>>   No.  It is a bug in the configuration files distributed for
> >>>>> libwxgtk.
> >>>>
> >>>> Unfortunately it seems to be a wide-spread bug. It is quite
> >>>> embarassing that a
> >>>> compile needs googling to fix it locally.
> >>>>
> >>>> Cannot "./configure" take care of this? I.e. add the "-lX11" flag if
> >>>> "something"?
> >>>
> >>> That "something" is exactly the problem.   Only some versions of
> >>> wxWidgets need this, and only for some configurations.   The
> >>> wx-config tool is supposed to tell us what libraries are needed so
> >>> we can link them.  But it doesn't mention X11.    So how are we to know?
> >>
> >> Actually, I think this is gnuplot's responsibility.  If I do
> >
> >> Anyway, I think gnuplot configure is obligated to add -lX11, given the
> >> situation.
> >
> > I think that ./configure is the place for tests of compile conditions.
> > There can be some simple case testing whether "-lX11" is needed or not.
> > Is such a workaround possible?
> 
> The necessary tests are already present.  The hunks of code that matter 
> have pre-processor conditionals:
> 
> #if defined(WX_NEEDS_XINITTHREADS) && defined(X11)
> #include <X11/Xlib.h>	/* Magic fix for linking against wxgtk3.0 */
> #endif
> 
> and WX_NEEDS_XINITTHREADS and X11 are defined from tests within the 
> configure process.
> 
> We only want to include library -lX11 for the building of wx_gui.cpp, 
> and there is a convenient definition for that:
> 
> Makefile:LIBRARIES_FOR_X =  -lX11
> 
> The included libraries for wx_gui.cpp are gotten from the wx-config 
> command as discussed earlier, and it shows up as
> 
> Makefile:WX_LIBS = -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 -lcairo 
> -lgobject-2.0 -lglib-2.0
> 
> So, all we really need do is append LIBRARIES_FOR_X to WX_LIBS if 
> XInitThreads() is used in the wx_gui code.  If X11 is not present, 
> LIBRARIES_FOR_X should be empty.
> 
> I've attached a six-line patch to the original bug report associated 
> with the inclusion of XInitThreads() here:
> 
> https://sourceforge.net/p/gnuplot/bugs/_discuss/thread/94192961/d1c5/attachment/gnuplot-wxlibs_xinitthreads_configure-djs2017jul06.patch

Unfortunately that doesn't work.

As it shows in the original bug report, wxgtk stupidly insists on the 
XInitThreads business  *even if the program doesn't use X11*. 

So making gnuplot's configuration rely on LIBRARIES_FOR_X doesn't
resolve the original problem.  It just moves the failure from compile-time
to run-time.  You can test this by configuring like this:

 ./configure --without-x --without-gd --with-wx

Your patch allows it to compile without complaint, but then you get
a run-time failure instead because wxgtk aborts when it finds that 
XInitThreads was not called.

This is actually worse than the compile-time failure because at that
point it's too late to fix the problem.  
Hence the warning in the Release Notes.

	Ethan


NB: --without-gd is there because the gd configure tool actually gets this right 
and pulls in -lX11 if libgd wants it. If the wxgtk configure tool did the same 
we wouldn't have this problem.
 




> 
> Dan
> 
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