Fwd: Re: 5.2 rc2 tarball now available

[Daniel J S. <dan...@ie...>]

On 07/06/2017 01:23 PM, sfeam wrote:
> On Thursday, 06 July 2017 12:38:13 Daniel J Sebald wrote:
>> On 07/05/2017 05:08 PM, Petr Mikulik wrote:
[snip]
>>> 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.

I see your point.  However, the user is requesting no X11, the 
consequence of which is a crash.  We could drop the "&& defined(X11)" in 
which case configuration will succeed but compilation then fail.  That's 
probably no better, so in addition to that we could place an error in 
configure.ac when wx_needs_xinitthreads is "yes" and X11 is not present.


> 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.

It isn't the wxgtk library that wants X11, it's gnuplot's use of 
XInitThreads() that requires X11.  wxgtk configure can't anticipate our 
use of an X function.  wx_gui shouldn't be using XInitThreads().  I 
suspect that something in the code outside the main thread is doing 
something graphics related, but that's much too complex to address in 
the near term.

Dan