Nested MSI and Makefile dependencies

[Michael Davidsaver via Tech-talk <tech-talk at aps.anl.gov>]

I have occasionally had situations where I wanted to include the output of one MSI substitutions file when expanding another.  To get the effect of a nested loop, or when I want one repeated section to be included in two final .db files.

In trying to make this work, I have continually struggled to get complete dependency lists for Make.  Below is the outcome of my most recent iteration, which is hopefully closer to correct.

To make up an example, suppose I have three files:

• top.substitutions (includes 'middle.db')
• middle.substitutions (includes 'leaf.template')
• leaf.template

I want to install only 'top.db'.  My Makefile would now look like:

TOP=../..
include $(TOP)/configure/CONFIG

DB += top.db

DBDDEPENDS_FILES += middle.db$(DEP)

include $(TOP)/configure/RULES

top.db$(DEP): $(COMMON_DIR)/middle.db

The two special lines, in order of effect:

top.db$(DEP): $(COMMON_DIR)/middle.db

This establishes the initial dependency.  The '.db$(DEP)' target is needed as the MSI dependency creation rule requires 'middle.db' to exist.

I do not find it necessary to have an explicit dependency "$(COMMON_DIR)/top.db: $(COMMON_DIR)/middle.db" for a clean build to succeed, but I am not certain why.  Is "$(DEP)" file creation somehow ordered first?  Or have I just been lucky so far?

Of course this dependency will appear in 'top.db$(DEP)' when it is created.  So no problem for incremental rebuild.

DBDDEPENDS_FILES += middle.db$(DEP)

For correct incremental rebuild, this assignment is necessary to include the '.db$(DEP)'.  Otherwise it is created, but not used.

This can be verified by "make -C O.$(T_A) PRINT.DBDDEPENDS_FILES" to see that both '.db$(DEP)' are listed.  And by patient inspection of the output of: "remake -C O.$(T_A) -p".