Colin Rafferty wrote: Whatever. The point is that src/extw-Xt.c uses the (presumably private) Xt function _XtWaitForSomething, which has either 7 or 8 arguments, depending upon whether libXt was compiled with -DXTHREADS. OK, that last suggestion was wrong. The logic of the Imake config files is fairly convoluted, but basically: In X11.tmpl: ProjectThreadsDefines defaults to -DXTHREADS In Threads.tmpl: LocalThreadsDefines defaults to ProjectThreadsDefines if LocalThreads is defined, THREADS_DEFINES is defined to include LocalThreadsDefines LocalThreads defaults to ThreadedProject In X11.tmpl: ThreadedProject defaults to ThreadedX ThreadedX is defined according to HasPosixThreads or HasCThreads, but most of the platform-specific config files (e.g. linux.cf) define ThreadedX themselves In Imake.tmpl: The definition of ALLDEFINES includes $(THREADS_DEFINES) /usr/src/xc/lib/Xt/Imakefile includes Threads.tmpl, so the presence or absence of -DXTHREADS in the compilation of libXt would appear to be determined by whether ThreadedX is defined (none of the other macros listed above appear to be overriden by any other Imake configuration files, or by the X Imakefiles). I would guess at something like: #include <Threads.tmpl> #if ThreadedX #define XTHREADS -DXTHREADS #else #define XTHREADS #endif test: ＠echo XTHREADS But how does one get this into configure? Alternatively, it may be simpler to just add a note to the PROBLEMS file suggesting --cflags='... -DXTHREADS' if XEmacs segfaults in _XtWaitForSomething when trying to control an external widget. -- Glynn Clements <glynn(a)sensei.co.uk&gt;