As a result of helping a user trying to build the filter test on

a linux variant system, I made some changes to (one hopes)
incorporate some improvements in documenting and building this test.

docs/filters.md

@@ -207,8 +207,11 @@ using bzip2. The test case is fragile and is only known to work for Linux
 and Cygwin. To avoid spurious failures, it must be explicitly
 invoked by entering the directory and issuing the command
 ````
-make clean all check
+make clean all makebzip2 check
 ````
+Note that the Make target 'makebzip2' creates the bzip2 shared object.
+It is the target most likely to fail when executed on an untested or
+non-standard platform.
 
 Although it is fragile, this test can  serve as a complete example for building
 plugins for other filters.

nc_test4/filter_test/H5Zbzip2.c

@@ -4,6 +4,8 @@
 #include <assert.h>
 #include <stdio.h>
 #include <hdf5.h>
+/* Older versions of the hdf library may define H5PL_type_t here */
+#include <H5PLextern.h>
 #include "h5bzip2.h"
 
 

nc_test4/filter_test/Makefile.am

@@ -44,13 +44,20 @@ if ENABLE_FILTER_TEST
 check_PROGRAMS = test_filter
 TESTS = tst_filter.sh
 
-all-local:
+# In order to create the bzip shared object,
+# we provide an explicit target for it that
+# must be invoked before 'make check'
+
+# You may need to change this if HDF5 is installed elsewhere
+HDF5LIBDIR = /usr/local/lib
+# Ditto for zlib
+ZLIBDIR = ${HDF5LIBDIR}
+
+makebzip2::
 	SDIR=${srcdir} ;\
 	for f in ${PLUGINSRC} ${BZIP2SRC} ; do \
         DLLSRC="$${DLLSRC} $${SDIR}/$$f" ; \
 	done ; \
 	gcc -g -O0 -shared -o ${LIBNAME} $${DLLSRC} \
-	-L/usr/local/lib -lhdf5_hl -lhdf5 -lz
+	-L${HDF5LIBDIR} -lhdf5_hl -lhdf5 -L${ZLIBDIR} -lz
 endif
-
-