Compile SOILWAT2 library with c++ when used for linking to unit tests

- close #82

- this required addressing following "error: cannot increment
expression of enum type 'Months'"
- use defined values for each month instead of `typdef enum` which
doesn't allow mathematical operations (easily); then define variables
as 'TimeInt' instead of 'Months'

SW_VegProd.c

@@ -85,7 +85,7 @@ void SW_VPD_read(void) {
 	/* =================================================== */
 	SW_VEGPROD *v = &SW_VegProd;
 	FILE *f;
-	Months mon = Jan;
+	TimeInt mon = Jan;
 	int x, lineno = 0;
 	const int line_help = 29;
 	RealF help_grass, help_shrub, help_tree, help_forb, help_bareGround, litt, biom, pctl, laic;

Times.c

@@ -166,7 +166,7 @@ TimeInt Time_lastDOY(void) {
 	return cum_monthdays[Dec];
 }
 
-TimeInt Time_days_in_month(Months month) {
+TimeInt Time_days_in_month(TimeInt month) {
 	/* =================================================== */
 
 	return days_in_month[month];

Times.h

@@ -48,9 +48,22 @@
 #define MAX_WEEKS 53
 #define MAX_DAYS 366
 
-typedef enum {
-	Jan, Feb, Mar, Apr, May, Jun, Jul, Aug, Sep, Oct, Nov, Dec, NoMonth
-} Months; /* note base0 */
+/* constants for each month; this was previously a typedef enum.
+ * Note: this has to be base0 and continuous. */
+#define Jan 0
+#define Feb 1
+#define Mar 2
+#define Apr 3
+#define May 4
+#define Jun 5
+#define Jul 6
+#define Aug 7
+#define Sep 8
+#define Oct 9
+#define Nov 10
+#define Dec 11
+#define NoMonth 12
+
 
 typedef unsigned int TimeInt;
 
@@ -74,7 +87,7 @@ void Time_set_mday(const TimeInt day);
 void Time_set_month(const TimeInt mon);
 time_t Time_timestamp(void);
 time_t Time_timestamp_now(void);
-TimeInt Time_days_in_month(Months month);
+TimeInt Time_days_in_month(TimeInt month);
 TimeInt Time_lastDOY(void);
 
 char *Time_printtime(void);

makefile

@@ -28,7 +28,6 @@ CFLAGS = -O3 -Wall -Wextra -pedantic -std=c11
 CXXFLAGS = -Wall -Wextra -std=gnu++11		# gnu++11 required for googletest on Windows/cygwin
 LDFLAGS = -L.
 LDLIBS = -l$(target) -lm						# order of libraries is important for GNU gcc (libSOILWAT2 depends on libm)
-gtest_ldlibs = $(LDLIBS) -l$(gtest)
 
 sources = SW_Main_lib.c SW_VegEstab.c SW_Control.c generic.c \
 					rands.c Times.c mymemory.c filefuncs.c \
@@ -45,6 +44,7 @@ Rpkg_objects = $(objects) SW_R_lib.o SW_R_init.o
 target = SOILWAT2
 bin_test = sw_test
 lib_target = lib$(target).a
+lib_target++ = lib$(target)++.a
 SHLIB = r$(target)$(SHLIB_EXT)
 
 gtest = gtest
@@ -53,7 +53,7 @@ GTEST_DIR = googletest/googletest
 GTEST_SRCS_ = $(GTEST_DIR)/src/*.cc $(GTEST_DIR)/src/*.h $(GTEST_HEADERS)
 GTEST_HEADERS = $(GTEST_DIR)/include/gtest/*.h \
                 $(GTEST_DIR)/include/gtest/internal/*.h
-
+gtest_LDLIBS = -l$(gtest) -l$(target)++ -lm
 
 
 all: $(SHLIB)
@@ -69,6 +69,12 @@ $(lib_target) :
 		ar -rcsu $(lib_target) $(objects)
 		@rm -f $(objects)
 
+$(lib_target++) :
+		$(CXX) $(CXXFLAGS) -c $(sources)
+		ar -rcsu $(lib_target++) $(objects)
+		@rm -f $(objects)
+
+
 bin : $(target)
 
 $(target) : $(lib_target)
@@ -94,9 +100,9 @@ $(lib_gtest) :
 			-pthread -c ${GTEST_DIR}/src/gtest-all.cc
 		ar -r $(lib_gtest) gtest-all.o
 
-test : $(lib_gtest) $(lib_target)
+test : $(lib_gtest) $(lib_target++)
 		$(CXX) $(CXXFLAGS) $(LDFLAGS) -isystem ${GTEST_DIR}/include -pthread \
-				test/*.cc -o $(bin_test) $(gtest_ldlibs)
+				test/*.cc -o $(bin_test) $(gtest_LDLIBS)
 
 test_run :
 		./$(bin_test)
@@ -108,7 +114,7 @@ clean :
 
 .PHONY : clean2
 clean2 :
-		@rm -f $(target) $(SHLIB) $(lib_target)
+		@rm -f $(target) $(SHLIB) $(lib_target) $(lib_target++)
 		@rm -f testing/$(target)
 		@rm -f testing/Output/*
 

test/test_rands.cc

@@ -15,13 +15,9 @@
 #include <time.h>
 #include <unistd.h>
 #include "../generic.h"
-#include "../generic.c"
 #include "../myMemory.h"
-#include "../mymemory.c"
 #include "../filefuncs.h"
-#include "../filefuncs.c"
 #include "../rands.h"
-#include "../rands.c"
 
 
 namespace {