add HDF5_H5_IS_DLL variable to switch the scenario when HDF5 is built…

… as a DLL (#1931)

gdal/frmts/hdf5/makefile.vc

@@ -7,7 +7,19 @@ OBJ		=	hdf5dataset.obj  hdf5imagedataset.obj \
 
 PLUGIN_DLL 	=	gdal_HDF5.dll
 
-EXTRAFLAGS 	= 	-I$(HDF5_DIR)\include -DWIN32 -D_HDF5USEDLL_ 
+EXTRAFLAGS = -I$(HDF5_DIR)\include -DWIN32 
+
+# From the HDF docs...
+# Users who want to build and run an application with HDF5 in Visual Studio
+# without using CMake should consult the USING_HDF5_VS.txt file. Building
+# applications with the dynamic/shared hdf5 libraries requires that the
+# "H5_BUILT_AS_DYNAMIC_LIB" compile definition be used.
+
+!IF "$(HDF5_H5_IS_DLL)" == "YES"
+EXTRAFLAGS 	= 	$(EXTRAFLAGS) -DH5_BUILT_AS_DYNAMIC_LIB 
+!ELSE
+EXTRAFLAGS 	= 	$(EXTRAFLAGS) -D_HDF5USEDLL_
+!ENDIF 
 
 !IF "$(HDF5_PLUGIN)" == "YES"
 EXTRAFLAGS = $(EXTRAFLAGS) -DHDF5_PLUGIN

gdal/nmake.opt

@@ -456,6 +456,10 @@ KAKADU_7_5_OR_LATER = YES
 #HDF5_DIR =	c:\warmerda\supportlibs\hdf5\5-164-win
 #HDF5_LIB =	$(HDF5_DIR)\dll\hdf5dll.lib 
 
+# Needed to define H5_BUILT_AS_DYNAMIC_LIB for windows compilation 
+# scenarios where it is not exported on the target (non-CMake builds)
+#HDF5_H5_IS_DLL = YES
+
 # Uncomment the following and update to enable KEA support.
 #KEA_PLUGIN = NO
 #KEA_CFLAGS = -Ic:\kea\include