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Created attachment 1469790 [details]
test case for reproducing

Description of problem:

Error: XtCreateWidget "glwidget" requires non-NULL widget class

It looks like this is due to the declaration of glwDrawingAreaWidgetClass in GLwDrawA.h, which comes with the mesa-libGLw-devel package. That header has the line:
GLAPI WidgetClass glwDrawingAreaWidgetClass;
And particularly with dynamic linking, if the actual object (glwDrawingAreaWidgetClass) is not found elsewhere, it is assumed to be a definition (since no extern). But then that new variable is NULL.

This has been working well declaring that variable (there are 2 GLAPI WidgetClass variables there) as extern:
extern GLAPI WidgetClass glwDrawingAreaWidgetClass;

Version-Release number of selected component (if applicable):

mesa-libGLw-devel-8.0.0-4

How reproducible:

every time.

Steps to Reproduce:
attaching test case
gcc -c test.c
gcc test.o -L/usr/lib64 -lGLU -lGL -lXm -lXt -lX11 -lGLw -o test
./test
Error: XtCreateWidget "glwidget" requires non-NULL widget class


Actual results:


Expected results:

No error


Additional info:

attaching patch / workaround, not sure if this is the best way to address the issue.

Created attachment 1469791 [details]
possible patch to /usr/include/GL/GLwDrawA.h

attached patch seems to address the issue

Created attachment 1470005 [details]
fixed patch, sorry about that

A test build of the upstream fix is available at:

https://people.redhat.com/ajackson/1607154

Since the problem described in this bug report should be
resolved in a recent advisory, it has been closed with a
resolution of ERRATA.

For information on the advisory, and where to find the updated
files, follow the link below.

If the solution does not work for you, open a new bug report.

https://access.redhat.com/errata/RHEA-2019:2120