sys/arduino/sketches: build sketches as a module

Generate a module for arduino sketches in a subfolder of BINDIR.
This prevents issues when doing concurrent builds or out of tree build with
readonly sources.

Declare all generated files as `BUILDDEPS` to be re-created after
`clean` on parrallel `clean all`.

dist/tools/arduino/pre_build.sh

@@ -1,24 +0,0 @@
-#!/bin/sh
-
-# check if at least the application dir and one sketch is given
-if [ $# -lt 2 ]
-then
-    echo "[Arduino pre-build] Error: not enough arguments given"
-    exit 1
-fi
-
-# 'consume' the application and arduino directories (first argument)
-SRCDIR=$1
-shift
-APPDIR=$1
-shift
-
-# create temporary file and put in the file header
-cat ${SRCDIR}/pre.snip > ${APPDIR}/_sketches.cpp
-# loop through the given sketches and include them into the temp file
-for sketch in $@
-do
-    cat ${sketch} >> ${APPDIR}/_sketches.cpp
-done
-# and prepend the file with the arduino bootstrapping code
-cat ${SRCDIR}/post.snip >> ${APPDIR}/_sketches.cpp

sys/arduino/Makefile.include

@@ -1,9 +1,15 @@
-# compile together the Arduino sketches of the application
-SKETCHES = $(wildcard $(APPDIR)/*.sketch)
-SRCDIR = $(RIOTBASE)/sys/arduino
+# Add Arduino sketches to the application as a module
 
-# run the Arduino pre-build script
-$(shell $(RIOTTOOLS)/arduino/pre_build.sh $(SRCDIR) $(APPDIR) $(SKETCHES))
+# Define application sketches module, it will be generated into $(BINDIR)
+SKETCH_MODULE     ?= arduino_sketches
+SKETCH_MODULE_DIR ?= $(BINDIR)/$(SKETCH_MODULE)
+SKETCHES           = $(wildcard $(APPDIR)/*.sketch)
+include $(RIOTBASE)/sys/arduino/sketches.inc.mk
+
+# Depends on module
+USEMODULE += $(SKETCH_MODULE)
+DIRS      += $(SKETCH_MODULE_DIR)
+BUILDDEPS += $(SKETCH_GENERATED_FILES)
 
 # include the Arduino headers
 INCLUDES += -I$(RIOTBASE)/sys/arduino/include

sys/arduino/doc.txt

@@ -56,24 +56,28 @@
  *
  * @subsection sec_concept_build Extension of the build system
  *
- * Building Arduino sketches in RIOT is done in a two step process.
+ * Building Arduino sketches in RIOT is done in a three step process.
  *
- * First, the make system calls a dedicated
- * [Arduino build script](https://github.com/RIOT-OS/RIOT/tree/master/dist/tools/arduino/pre_build.sh),
- * which is called from the
+ * First, the make system defines a generated `arduino_sketches` module placed
+ * into `$(BINDIR)`
+ * [Arduino sketches makefile](https://github.com/RIOT-OS/RIOT/tree/master/sys/arduino/sketches.inc.mk),
+ * which is included from the
  * [Makefile.include](https://github.com/RIOT-OS/RIOT/tree/master/sys/arduino/Makefile.include)
  * of the RIOT Arduino module.
+ * The generated module is added to used modules and build directories.
  *
- * This script creates a temporary file called '_sketches.cpp' inside the
- * application folder. Into this file, the script copies some Arduino glue code (
+ * Second, as prerequisites for the `link` target, the make system will create
+ * the module into `$(BINDIR)/arduino_sketches` with an `arduino_sketches.cpp`
+ * source file.
+ * Into this file, it copies some Arduino glue code (
  * [pre.snip](https://github.com/RIOT-OS/RIOT/blob/master/sys/arduino/pre.snip)
  *  and
  * [post.snip](https://github.com/RIOT-OS/RIOT/blob/master/sys/arduino/post.snip))
  * together with the contents of all `*.sketch` files contained in the
  * application folder.
  *
- * Second, the RIOT make system is called as usual, processing the temporary
- * file containing all the Arduino code. Simple :-)
+ * Third, the RIOT make system is called as usual, building the generated
+ * library with the Arduino code and including it in the final firmware.
  *
  * @subsection sec_conecpt_api Implementation of the Arduino API
  *

sys/arduino/sketches.inc.mk

@@ -0,0 +1,34 @@
+# Compile together the Arduino sketches of the application
+# They are declared a as new module $(SKETCH_MODULE) in $(SKETCH_MODULE_DIR)
+
+ifndef SKETCH_MODULE
+  $(error SKETCH_MODULE undefined. It should be defined to the sketches module name)
+endif
+ifndef SKETCH_MODULE_DIR
+  $(error SKETCH_MODULE_DIR undefined. It should be defined to the sketches module directory)
+endif
+ifndef SKETCHES
+  $(error SKETCHES undefined. It should be defined to the list of sketches files)
+endif
+
+SNIPDIR         = $(RIOTBASE)/sys/arduino
+SKETCHES_ALL    = $(SNIPDIR)/pre.snip $(SKETCHES) $(SNIPDIR)/post.snip
+SKETCH_CPP     ?= arduino_sketches.cpp
+SKETCH_GENERATED_FILES = $(SKETCH_MODULE_DIR)/Makefile $(SKETCH_MODULE_DIR)/$(SKETCH_CPP)
+
+# Building the module files
+#   Do not use $^ in receipes as Makefile is also a prerequisite
+$(SKETCH_MODULE_DIR)/Makefile: $(SKETCH_MODULE_DIR)/$(SKETCH_CPP)
+	$(Q)echo 'SRCXX = $(SKETCH_CPP)'               > $@
+	$(Q)echo 'include $$(RIOTBASE)/Makefile.base' >> $@
+$(SKETCH_MODULE_DIR)/$(SKETCH_CPP): $(SKETCHES_ALL)
+	@mkdir -p $(@D)
+	$(Q)cat $(SKETCHES_ALL) > $@
+
+# Make everything rebuild if current makefile changes
+_ARDUINO_SKETCHES_MAKEFILE := $(lastword $(MAKEFILE_LIST))
+$(SKETCH_MODULE_DIR)/$(SKETCH_CPP): $(_ARDUINO_SKETCHES_MAKEFILE)
+$(SKETCH_MODULE_DIR)/Makefile: $(_ARDUINO_SKETCHES_MAKEFILE)
+
+# HACK Rebuild cpp files everytime in case one of the `SKETCHES` is deleted
+$(SKETCH_MODULE_DIR)/$(SKETCH_CPP): FORCE