==========================================================
CPW Pt.4 Recursive Descent Parser, CPW Pt.5 Unique Strings
==========================================================

- C Programming Workout Part 4: A __recursive descent parser__ for a calculator.
- C Programming Workout Part 5: A data structure for __unique strings__.

Fix the Makefile for the ABC Compiler Project!
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
The makefile from session 13 has a bug. If you have more than one test program
you will get a linker error.  

In the makefile you have to change the lines

---- CODE (type=mk) ------------------------------------------------------------
# our rule: to build target link its object file against library object files
%: %.o $(obj) | $(obsolete.deps)
	$(CC) -o $@ $(LDFLAGS) $^
--------------------------------------------------------------------------------

into

---- CODE (type=mk) ------------------------------------------------------------
# our rule: to build target link its object file against library object files
%: %.o $(lib.o) | $(obsolete.deps)
	$(CC) -o $@ $^ $(LDFLAGS)
--------------------------------------------------------------------------------

Here the complete makefile with the fix:

:import: session13/abc/Makefile [fold]

After the bug fix you should of course commit it to your git repository.

Optional Modification for the Makefile
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
We use variables like _CC_, _CPPFLAGS_, _LDFLAGS_ in our makefile for selecting
the compiler and specifying flags to the linker. You know that you can
predefine these variables when you run make. For example

---- CODE (type=txt) -----------------------------------------------------------
make CPPFLAGS="-Wall -DNDEBUG -O3" LDFLAGS=-lm
--------------------------------------------------------------------------------

If you would like to have this value hard coded in the makefile simply add a
definition like this (quotes are then not needed):

---- CODE (type=txt) -----------------------------------------------------------
CPPFLAGS    := -Wall -O3
LDFLAGS	    := -lm
--------------------------------------------------------------------------------

Of course, hard coding values has disadvantages. You now longer change this
values when you invoke make from the command line. A better alternative might
be to add certain default values:

---- CODE (type=txt) -----------------------------------------------------------
CPPFLAGS    += -Wall	# always use -Wall for the compiler
LDFLAGS	    += -lm	# always link against the math library
--------------------------------------------------------------------------------

It extends the variables for some additional values that you always want to
have. Now with

---- CODE (type=txt) -----------------------------------------------------------
make CPPFLAGS="-DNDEBUG -O3" LDFLAGS=-lm
--------------------------------------------------------------------------------

you compile with _CPPFLAGS="-DNDEBUG -Wall -O3"_ and _LDFLAGS=-lm_. And with

---- CODE (type=txt) -----------------------------------------------------------
make
--------------------------------------------------------------------------------

you only use the defaults _CPPFLAGS="-Wall"_ and _LDFLAGS=-lm_.


:links: recursive descent parser -> doc:session17/page02
	unique strings -> doc:session17/page03