Makefile and linking .a libraries

Question

I've got a src folder which, after running make, creates 4 libraries in .a format. There's also a folder tests which contains tests.cpp. This file depends on the libraries previously mentioned.

I'm trying to get a Makefile inside tests that generates the libraries inside src (this it does) and then uses these to compile tests.cpp (this it doesn't - I get many many undefined references, as if it weren't linking properly).

The folder tests contains this Makefile:

include ../src/makefile.inc

DIR = ../src
OBJLIBS = ../src/CapaFisica.a ../src/CapaLogica.a ../src/CapaInterfaz.a ../src/Utilitarios.a

TARGETS = tests.cpp
EXE = tests

all : $(EXE)

%.a :
    -for d in $(DIR); do (cd $$d; $(MAKE)); done

tests:  $(OBJLIBS)
    $(CC) $(CFLAGS) $(OBJLIBS) -o $@ $(TARGETS)

clean :
    $(ECHO) Borrando archivos.
    -$(RM) -f ./tests
    cd $(DIR); make clean
    find . -name "*.o" -type f -print | xargs /bin/rm -f

What am I doing wrong?

What happens when you try to build `tests` by hand, without the makefile? — Beta, Apr 28 '13 at 00:03
The same, many undefined references. The .o files I need are not the same directory as the `.a` files, does this matter? — Maria Ines Parnisari, Apr 28 '13 at 00:08
yes - you probably need something like /LIBPATH:../src (or more, depending on where you build, and depending on your compiler/linker) — Scott Jones, Apr 28 '13 at 00:13
@Beta, my concern is that the file `tests.cpp` has many `#include *.h`. Do I need to replace these with something? — Maria Ines Parnisari, Apr 28 '13 at 00:43
I take it you didn't write `tests.cpp`. Are you sure that it worked for the author? — Beta, Apr 28 '13 at 01:37

score 2 · Accepted Answer · edited May 23 '17 at 11:49

gcc linker is sensitive about the order of .o files and static libraries specified on the command line.

Replacing

    $(CC) $(CFLAGS) $(OBJLIBS) -o $@ $(TARGETS)

with

    $(CC) $(CFLAGS) -o $@ $(TARGETS) $(OBJLIBS)

might help. Also make sure that .a files in $(OBJLIBS) are in the correct order if they depend on each other. Depending library must be on the command line before the library which defines the symbols.

For more details see this question: Why does the order in which libraries are linked sometimes cause errors in GCC?

Makefile and linking .a libraries

1 Answers1