# 
# makefile to generate dependencies for C programs automatically
# based on example from GNU make manual (under heading "Generating 
# Prerequisites Automatically")
#

# override options for implicit rule(s)
CC = gcc # since we make use of gcc feature -MM

#
# treat .o files as "intermediate" files so they can be deleted
# automatically
# 
# (FIXME this does not always work as hoped-for -- ?)
#
.INTERMEDIATE:	$(wildcard *.o)

#
# rule to make .d files for all .c files
#
sources =  $(wildcard *.c)
dependfiles = $(sources:.c=.d)

alldepend:  $(dependfiles)

#
# include all files of prerequisites
#
include $(wildcard *.d) $(wildcard *.depend)

#
# pattern rule for generating files of prerequisites
# (mostly copied from GNU make manual)
#
# to find out what the "sed" does, try "gcc -MM pgm.c" and compare
# result to what this makefile generates as pgm.d
#
%.d: %.c
	@echo remaking dependency file $@
	@set -e; \
		$(CC) -MM $(CPPFLAGS) $< \
		  | sed 's/\($*\)\.o[ :]*/\1.o $@ : /g' > $@; \
		[ -s $@ ] || rm -f $@

#
# cleanup
#
.PHONY:  dclean
dclean:
	-rm $(dependfiles)