2

I am trying to built two different libraries from fortran source code, one with OMP support, the other without. Thus %.o files from the same source differ dependent on the compiler flags. When changing/recompiling one source file, ar still needs all o-files to rebuild the library. To avoid recompiling all source files I want to store the o-files from un-changed source files in two different directories, one with o-files including omp support, the other with out. I am happy to have to makefiles for that in that directory where the libraries are finally located.

However, I cannot get the library rebuild in a single command because of the vpath variable behaviour. Here is the make file:

   SRC :=
   FORTRAN  = ifort
   OPTSSEQ = -mkl=sequential -DThreadUnSafe -warn nounused -warn declarations -O3 -DTIMEDETAIL
   DRVOPTS  = $(OPTS)
   NOOPT    =
   LOADER   = ifort
   LOADOPTS =
   kernel=$(shell uname -r)
   ARCH     = ar
   ARCHFLAGS= cr
   RANLIB   = ranlib
   LibName=Lib_LM_$(FORTRAN)_$(kernel)_1.0.a
  .SUFFIXES:
  .SUFFIXES: .f90 .o
   include Moduls.mk
   vpath %.f90 src/
   vpath %.o NoOMP/
   OBJS = $(patsubst %.f90,%.o,$(SRC))
   $(LibName): $(OBJS)
      $(ARCH) $(ARCHFLAGS) $@ $?
      $(RANLIB) $@
   %.o : %.f90
      $(FORTRAN) $(OPTSSEQ) -c $? -o $(addprefix NoOMP/,$@)
   clean:
     -rm *.mod
     -rm NoOMP/*.o
     -rm *.smod
     -rm $(LibName)

This results in successful building all %.o files after "make clean", since all %.f90 files are read from src/ and all %.o files are written to NoOMP/. However, building the archive fails because the "NoOMP" prefix on the %.o files is dropped. Thus, ar complains that it cannot find the %.o files. Only if I run "make" again, the archive is build because then %.o files have the NoOMP prefix. Adding a prefix command to the archive build line works fine if it is build from scratch. However, if only a single file has changed, the unchanged files have a "NoOMP/NoOMP/" prefix, resulting in an abort again.

While this is terribly annoying, as far as I understood the manual that is the default behaviour of GNU make. If I am wrong, how can I repair the makefile, if I am right how can I circumvent this problem.

2

Solved

the examples work when changing the line

    $(ARCH) $(ARCHFLAGS) $@ $?

to

    $(ARCH) $(ARCHFLAGS) $@ $(addprefix NoOMP/,$?)

Above I had ruled out this solution, but my trial where based on $^ instead of $?. While the first will rebuilt the whole archive from old and new %.o files, the last will only update the existing archive with new %.o files. When rebuilding the whole archive from old and new %.o files, old %.o files will have the wrong prefix, new the right. Thus excluding old %.o files by updating the archive with newly compiled %.o files circumvents that problem.

Cheers

Your Answer

By clicking “Post Your Answer”, you agree to our terms of service, privacy policy and cookie policy

Not the answer you're looking for? Browse other questions tagged or ask your own question.