CODEWITHSUNDEEP
c++makefilebuild
Manfredo
Manfredo

Reputation: 1740

Makefile: no rule to make target: how to set the correct rules?

I have a project that I am trying to create a Makefile for. The folder structure looks like this:

|-- bin
|-- build
|-- Makefile
|-- src
|   |-- some_files.cpp
|   |-- some_files.h
|   |-- ForestFactory
|   |-- MMParSet
|   |-- century
|       |-- century_carbon.cpp
|       |-- century_carbon.h
|   `-- grass
`-- src_multithread
    |-- __history

and I have tried to use this reference to create a Makefile. The Makefile I have is 

CC := g++

SRCDIR := src
BUILDDIR := build
TARGETDIR := bin
INSTALLBINDIR := /usr/local/bin
TARGET := bin/formind

# CPP files
SOURCES := $(shell find $(SRCDIR) -type f -name *.cpp)
# remove the src path and add the build path and the .o extension
OBJECTS := $(addprefix $(BUILDDIR)/,$(patsubst %.cpp,%.o,$(notdir $(SOURCES))))

CFLAGS := -std=c++11 -stdlib=libc++

INC := -I/usr/local/include -I $(SRCDIR) -I $(SRCDIR)/century -I $(SRCDIR)/grass -I $(SRCDIR)/MMParSet -I $(SRCDIR)/ForestFactory

$(TARGET): $(OBJECTS)
    @mkdir -p $(TARGETDIR)
    @echo " Linking..."
    @echo " $(CC) $^ -o $(TARGET)"
    $(CC) $^ -o $(TARGET)

$(BUILDDIR)/%.o: $(SRCDIR)/%.cpp
    @mkdir -p $(BUILDDIR)
    @echo " $(CC) $(CFLAGS) $(INC) -c -o $@ $<"
    $(CC) $(CFLAGS) $(INC) -c -o $@ $<

clean:
    @echo " Cleaning...";
    @echo " $(RM) -r $(BUILDDIR) $(TARGET)"
    $(RM) -r $(BUILDDIR) $(TARGET)


.PHONY: clean

When I try to make I get the following error message:

make: *** No rule to make target `build/century_carbon.o', needed by `bin/formind'.  Stop.

The source files come from a nested set of subdirectories inside src. My understanding was that the OBJECTS variable should contain the complete paths of the final object files, so that I have something like

$SOURCES = src/century/century_carbon.cpp ... src/for_branching.cpp ... src/grass/grass_log.cpp ...

$OBJECTS = build/century_carbon.o ... build/for_branching.o ... build/grass_log.o ...

Is there something wrong in the way I wrote the compilation rules?

Upvotes: 2

Views: 7282

Answers (1)

Joseph Quinsey
Joseph Quinsey

Reputation: 9952

The problem is with the nested source directory century. If you add to the makefile:

info:
    @echo " Info..."
    @echo " SOURCES = $(SOURCES)"
    @echo " OBJECTS = $(OBJECTS)"

then make info gives:

  Info...
  SOURCES = src/century/century_carbon.cpp src/some_files.cpp
  OBJECTS = build/century_carbon.o build/some_files.o

This check shows that your construction of these macros is ok. And it also shows, as you report, that make will then tell us:

make: *** No rule to make target 'build/century_carbon.o', needed by 'bin/formind'.  Stop.

If you add an additional rule, with the directory century specified:

$(BUILDDIR)/%.o: $(SRCDIR)/century/%.cpp
    @mkdir -p $(BUILDDIR)
    $(CC) $(CFLAGS) $(INC) -c -o $@ $<

then your build will proceed.

An alternative solution is to use VPATH. Add the line:

VPATH = src:src/century

and also remove $(SRCDIR)/ from your rule, which now becomes:

$(BUILDDIR)/%.o: %.cpp
    @mkdir -p $(BUILDDIR)
    $(CC) $(CFLAGS) $(INC) -c -o $@ $<

Update: The above answer could be improved in two ways:

  • Use vpath rather than VPATH, for more precise control of the searches.

  • Automatically generate the argument for vpath / VPATH.

This is suprisingly simple: just replace my hard-coded VPATH line with:

vpath %.cpp $(sort $(dir $(SOURCES)))

Upvotes: 3

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