clang: warning: -l*: 'linker' input unused

Question

When I compile code using GNU Make I get multiple warnings like:

clang: warning: -lGui: 'linker' input unused

This is probably because I have messed something up in my Makefile (below). Can anyone point me toward the problem?

CXX=g++
CC=g++
CXXFLAGS=-g -Wall -W -Wshadow -Wcast-qual -Wwrite-strings $(shell root-config --cflags --glibs)
CPPFLAGS+=-MMD -MP
LDFLAGS=-g $(shell root-config --ldflags)
LDLIBS=$(shell root-config --libs)

xSec_x: xSec_x.o xSec.o Analysis.o
-include xSec_x.d xSec.d Analysis.d

xSec.o: xSec.cpp xSec.h Analysis.h Analysis.cpp

xSec_x.o: xSec_x.cpp xSec.h Analysis.h

clean:
    rm -f @rm -f $(PROGRAMS) *.o *.d

MadScientist · Accepted Answer · 2013-11-04 19:02:01Z

18

That message means you are passing linker flags (like -l which tells the linker to pull in a library) to the compiler.

This means that the result of running root-config --cflags --glibs is generating linker flags, and those are going into CXXFLAGS, which is being passed to the compiler. I don't know what root-config is, but you should investigate its command line and invoke it in a way where it doesn't generate linker flags. Probably removing the --glibs option will do it.

ETA: you really want to be using := to assign these flags variables if you're going to run $(shell ...) there. It will work either way, but if you use = then the shell command will be run every time make expands the variable, which is once per compilation. If you use := it will only be run once, when the makefile is parsed.

answered Nov 4, 2013 at 19:02

MadScientist

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1 Comment

Navin Over a year ago

D'oh! I was passing all the linker flags to the compiler... I wish clang was a little more descriptive. The error makes it sound like the lib was ignored because the code never used its symbols.

wogsland · Accepted Answer · 2016-04-22 18:12:01Z

8

I got this same error and the reason was that I forgot to add -I in front of my included paths for cflags in makefile. For example:

CFLAGS += $(path)/dir/subdir/include     -> Got the above mentioned error.
CFLAGS += -I$(path)/dir/subdir/include   -> Fixed the issue.

edited Apr 22, 2016 at 18:12

wogsland

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answered Apr 22, 2016 at 17:53

ManyuBishnoi

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