make - specify library to link from the command line (without Makefile)

Question

For simple program eg, proc.c which has only one source file, it's convenient to compile and link using just make proc, which by default search for proc.c and create proc as output file. There is no need to create a Makefile for that.

If proc.c requires to link with some library such as the math library (defined by <math.h>). Using gcc directly, we can use gcc -c proc.c -o proc -lm. Is there an equivalent make command line option to specify -lm so we can use make command directly without writing a Makefile?

Similar task suggested by Basile Starynkevitch:

Makefile with Multiple Executables

I believe you should write a *simple* `Makefile` like [this one](http://stackoverflow.com/a/16751650/841108) — Basile Starynkevitch, Jan 10 '16 at 08:33

score 1 · Accepted Answer · edited May 23 '17 at 12:26

1

Link library with make without makefile

If your source file is prova.c then you can do the following:

$> export LDFLAGS=-lm; make prova

or:

$> export LDLIBS=-lm; make prova    # LDLIBS works on Linux (but LDFLAGS doesn't)

or:

$ make prova LDLIBS=-lm

as Make uses this implicit rule:

%: %.o    # Link object file
    $(CC) $(LDFLAGS) n.o $(LOADLIBES) $(LDLIBS)

Make has several implicit rules, you can see all of them with make -p. For further information see this post.

edited May 23 '17 at 12:26

Community

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answered Jan 10 '16 at 08:01

terence hill

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thanks, but does this actually work? I tried a `fmod` function in `proc.c` and using your command it still reported `undefined reference to `fmod'` – artm Jan 10 '16 at 08:13
perhaps `make prova LIBES=-lm` – Basile Starynkevitch Jan 10 '16 at 08:22
Tried again on a linux box (I was on OS X), worked with the above but not with gcc prova.c. As suggested by @Basile, try also LIBS. – terence hill Jan 10 '16 at 08:29
ok I'm on Linux (Ubuntu) and `LDLIBS=-lm` works (the first `LDFLAGS` doesn't) – artm Jan 10 '16 at 09:41
@BasileStarynkevitch - yes it works with `make prova LDLIBS=-lm` – artm Jan 10 '16 at 11:10
@BasileStarynkevitch I guess Basile means LIBES not LIBS as LOADLIBES is also added in the linker line. And in fact for me works if you set LOADLIBES=-lm – terence hill Jan 10 '16 at 11:16

make - specify library to link from the command line (without Makefile)

1 Answers1

Link library with make without makefile