added build option: USE_JAVAH - explicitly enable/disable use of javah over javac -h (if autodetect doesnt work correctly)

Makefile.conf

@@ -5,10 +5,12 @@
 
 HERE:=$(dir $(lastword $(MAKEFILE_LIST)))
 PLATFORM:=$(shell uname | tr A-Z a-z)
+JAVAC_CMD=javac -encoding UTF-8
+JAVAH_CMD=javah -encoding UTF-8
 
 # DEV ENV PATHS & CFG
-# The dev environment paths and configs are set to a default value which can be overridden by ./local.conf and overridden again by <subdir>/local.conf
-######### Build Config Defaults #########
+# The build settings are set to a default value which can be overridden by using ./local.conf
+#########  DEFAULTS #########
 DEBUG=0
 PREFIX=$(HOME)
 YML2_PATH=$(PREFIX)/src/yml2
@@ -19,14 +21,13 @@ ENGINE_INC_PATH=$(PREFIX)/include
 AD_LIB_PATH=$(PREFIX)/lib
 AD_INC_PATH=$(PREFIX)/include
 
+
 ### Guessing JAVA_HOME
 ifeq ($(PLATFORM),linux)
     JAVA_HOME=$(subst /bin,,$(dir $(realpath /usr/bin/javac)))
 endif
 
 
-JAVAC_CMD=javac -encoding UTF-8
-JAVAH_CMD=javah -encoding UTF-8
 
 ######### Overrides from the config file(s) #########
 ifneq ("$(wildcard $(HERE)local.conf)","")
@@ -46,10 +47,15 @@ ifndef JAVA_HOME
     $(error JAVA_HOME is not set!)
 endif
 
-# Old versions of a Java distribution have a `javah` binary, new versions do not. This checks whether or not `javah` can be found in the Java distribution found in the directory `$JAVA_HOME`.
-DUMMY:=$(shell which $(JAVA_HOME)/bin/javah)
-ifeq ($(.SHELLSTATUS),0)
-    OLD_JAVA=true
+# Guessing USE_JAVAH
+# cant be guessed earlier, because we depend on JAVA_HOME which can be set in the local.conf
+# Old versions of a Java distribution have a `javah` binary, new version do not and the replacement is "javac -h"
+# TODO: dont check for presence of javah, but check if javac -h is supported, because some java (RHEL) has javah but supports javac -h
+ifndef USE_JAVAH
+	DUMMY:=$(shell which $(JAVA_HOME)/bin/javah)
+	ifeq ($(.SHELLSTATUS),0)
+		USE_JAVAH=1
+	endif
 endif
 
 JAVA_BIN_DIR=$(JAVA_HOME)/bin

local.conf.example

@@ -14,6 +14,7 @@
 
 ############ JAVA ##############
 # JAVA_HOME=/Library/Java/JavaVirtualMachines/jdk1.8.0_231.jdk/Contents/Home
+# USE_JAVAH=0   # keep the build from using javah
 
 ############ YML2 ##############
 # YML2_PATH=$(HOME)/src/yml2

src/Makefile

@@ -33,6 +33,7 @@ $(info PLATFORM:        $(PLATFORM))
 $(info DEBUG:           $(DEBUG))
 $(info CXX:             $(CXX))
 $(info JAVA_HOME:       $(JAVA_HOME))
+$(info USE_JAVAH:       $(USE_JAVAH))
 $(info ENGINE_LIB_PATH: $(ENGINE_LIB_PATH))
 $(info ENGINE_INC_PATH: $(ENGINE_INC_PATH))
 $(info AD_LIB_PATH:     $(AD_LIB_PATH))
@@ -145,7 +146,7 @@ gen-jni-headers: codegen $(JNI_GENERATED_HH)
 # "new" javac -h accepts list of java files
 # While "old" (Java 8) javah needs a list of java classes (e.g. foundation.pEp.jniadapter.Message)
 $(JNI_GENERATED_HH):
-ifdef OLD_JAVA
+ifeq ($(USE_JAVAH),1)
 	cd $(JAVA_BUILD_ROOT)/;$(JAVA_BIN_DIR)/$(JAVAH_CMD) -d ../../src/$(CXX_DIR) $(subst ${ },${space}\${\n}, $(subst /,.,$(subst $(JAVA_BUILD_ROOT),,$(basename $(sort $(wildcard $(JAVA_BUILD_ROOT)$(JAVA_PKG_BASENAME)*.class/))))))
 else
 	cd $(JAVA_DIR);$(JAVA_BIN_DIR)/$(JAVAC_CMD) -d ../$(JAVA_BUILD_ROOT) -h ../$(CXX_DIR)/ $(JAVA_PKG_BASENAME)/*.java