如何将 pkg-config 添加到 Makefile？

Question

My Makefile looks like this :

all:main.cpp
    g++ -I../../DrAPI/ -Wl,--no-as-needed -ldl -lrt -o SampleApp01 $< 
clean:
    rm -f SampleApp01

this is what I would do without Makefile:

gcc main.cpp -o test $(pkg-config --cflags --libs libmongoc-1.0)

now because of importing DrAPI I have to use Makefile to include that API as well, but I would lose libmongoc-1.0 without pkg-config. In that case, how should I add $(pkg-config --cflags --libs libmongoc-1.0) into my Makefile so that it works?

Answer 1

I would have made a Makefile that looks like this, so it use the rules that are already in make(1) . Try make -f /dev/null --print-data-base to see them. Suggest grep -ing COMPILE.c and LINK.c to get the important stuff. COMPILE.cpp , COMPILE.C and COMPILE.cxx are for c++ and COMPILE.c are for c.

#!/bin/make
# Makefile
# 2020-02-10 Anders Jackson

# Basic setup
CXX       = g++
CXXFLAGS  = -c -g -Wall -Wextra
CXXFLAGS += -I../../DrAPI/
LDFLAGS   =
LDLIBS    = -ldl -lrt

# `pkg-config --list-all | grep -e mongo` will find if installed
# Here is the libmongoc-1.0 setup.
CXXFLAGS += `pkg-config --cflags          libmongoc-1.0`
LDFLAGS  += `pkg-config --libs-only-L     libmongoc-1.0`
LDLIBS   += `pgk-config --libs-only-other libmongoc-1.0`
LDLIBS   += `pkg-config --libs-only-l     libmongoc-1.0`

# Adjusting for this project
SOURCES = main.cpp
OBJECTS = $(SOURCES:.cpp=.o)

EXECS = main

all: $(EXECS)      # Link exec from objects
$(OBJECTS):        # Make all .o from .cpp (no local header files)

clean:
      -rm $(OBJECTS)
      -rm $(EXECS)
# eof

Notice that here there that object files only has dependencies on the source file. If a source file has some local header file dependencies, you need to add them manually.

This file also see to that when linking, those -L switches are before object files and -l switches are after. If you try to just use just one pkg-config --libs in LDFLAGS , it will not work. I also just add one thing at the time to the variables with += , like for LDLIBS , as it makes it easier to see what is added.

The built in rules are:

OUTPUT_OPTION = -o $@
# Compilation for C and C++
COMPILE.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $(OUTPUT_OPTION) $<
COMPILE.cpp = $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(TARGET_ARCH) -c $(OUTPUT_OPTION) $<
# Linking for C and C++
LINK.c = $(CC) $(CFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH) $^ $(LOADLIBES) $(LDLIBS) -o $@
LINK.cpp = $(CXX) $(CXXFLAGS) $(CPPFLAGS) $(LDFLAGS) $(TARGET_ARCH) $^ $(LOADLIBES) $(LDLIBS) -o $@

It helps to understand which variable goes where.

Answer 2

all:main.cpp g++ -I../../DrAPI/ `pkg-config --cflags --libs libmongoc-1.0` -Wl,--no-as-needed -ldl -lrt -o SampleApp01 $< clean: rm -f SampleApp01

Answer 3

When I compile my C code using the GTK+ library I create a variable called GTK and set it to pkg-config like this:

GTK = `pkg-config --cflags --libs gtk+-3.0`

Compiling the code using:

$(CC) $(CFLAGS) $(OBJECTS) $(GTK) -o $@

Where CC = gcc , CFLAGS are some other compiler flags (like -I ../../DrAPI ) and OBJECTS are the source and object files.

This way your makefile could look like this:

DRAPI = `pkg-config --cflags --libs libmongoc-1.0`

all:main.cpp
    g++ -I../../DrAPI/ -Wl,--no-as-needed -ldl -lrt $(DRAPI) -o SampleApp01 $< 
clean:
    rm -f SampleApp01

EDIT : Forget about this. Use a CFLAGS variable and store pkg-config --cflags [some library, eg. gtk+-3.0] pkg-config --cflags [some library, eg. gtk+-3.0] and a LIBS variable to store pkg-config --libs [some library again] . Now your makefile could look like this:

CFLAGS = -I../../DrAPI/ -Wl,--no-as-needed -ldl -lrt `pkg-config --cflags libmongoc-1.0`
LIBS = `pkg-config --libs libmongoc-1.0`

all:main.cpp
    g++ $(CFLAGS) $(LIBS) -o SampleApp01 $< 
clean:
    rm -f SampleApp01

Hope this helps!