-# Find sources files and get the corresponding object names
-# The first argument should be the sources extension ("c" or "cpp" typically)
-# It expects the variable $T and $O to be defined as commented previously in
-# this file.
-find_objects = $(patsubst $T/%.$1,$O/%.o,$(shell find $C -name '*.$1'))
+# Find sources files and get the corresponding object names. The first
+# argument should be the sources extension ("c" or "cpp" typically). The
+# second argument is where to search for the sources ($C if omitted). The
+# resulting files will always have the suffix "o" and the directory rewritten
+# to match the directory structure (from $T) but in the $O directory. For
+# example, if $T is "/usr/src", $O is "/tmp/obj", $C is "/usr/src/curr" and it
+# have 2 C sources: "/usr/src/curr/1.c" and "/usr/src/curr/dir/2.c", the call:
+# $(call find_objects,c)
+# Will yield "/tmp/obj/curr/1.o" and "/tmp/obj/curr/dir/2.o".
+find_objects = $(patsubst $T/%.$1,$O/%.o,$(shell \
+ find $(if $2,$2,$C) -name '*.$1'))