Re: Request for critique on a small makefile

[Philip Guenther]

On 12/11/06, Edward Z. Yang <address@hidden> wrote:
...
> So, here is a fairly simple Makefile that works. I would like to know if
> I did anything wrong, went against any good practice, i.e. did anything
> that could become a bad habit. How portable is this Makefile? Thanks!

First off, you should take a look at Paul Smith's rules for makefiles:
    http://make.paulandlesley.org/rules.html

You current makefile violates rules 2, 3, and 4 from that page.
Rather than try to do a line-by-line analysis, let me show how I would
write the makefile for building those two programs:

boostdir = /usr/include/boost-1_33_1
boostlib = -lboost_program_options-gcc-mt-s

# these next two variables are used by make's builtin pattern rules
CXXFLAGS = -ansi -pedantic
CPPFLAGS = -I${boostdir}

programs = fibonacci printNumbers

all : ${programs}

clean:
       ${RM} ${programs} *.o

fibonacci: fibonacci.o
       ${LINK.cc} -o $@ $< ${boostlib}


Notes:
- the source files aren't mentioned at all.  Instead, I practice my
laziness and let
  make's pattern rules figure out how to create the .o files
- as it traditionaly under UNIX, the executables don't have a .exe
suffix.  If you *really*
  want the suffix, you would do the following:
  1) change the value of the 'programs' variable
  2) add the .exe suffix to just the target in the rule for linking fibonacci
  3) add a rule for linking printNumbers.exe similar to the one for
fibonacci.exe
- the object files are left in the current directory.  Don't change
this without first
  reading all of Paul's webpages on Make at http://make.paulandlesley.org/

Here's the output of make -n with that makefile in a directory
containing files fibonacci.cpp and printNumbers.cpp:

$ gmake -n
g++ -ansi -pedantic -I/usr/include/boost-1_33_1  -c -o fibonacci.o fibonacci.cpp
g++ -ansi -pedantic -I/usr/include/boost-1_33_1   -o fibonacci
fibonacci.o -lboost_program_options-gcc-mt-s
g++ -ansi -pedantic -I/usr/include/boost-1_33_1   printNumbers.cpp
-o printNumbers

If you aren't sure what pattern rules or variables are builtin to your
copy of GNU make, you can dump the entire set using the following
command:

gmake -pq -f/dev/null

That generates 1085 lines of output on my system, so you may want to
redirect it to a file or pipe it to 'less'...

Does that help at all?


Philip Guenther