CODEWITHSUNDEEP
makefile
Teofrostus
Teofrostus

Reputation: 1596

Why doesn't this make file work?

CC=g++
CFLAGS=-Wall -ggdb
OBJDIR=Objects
SRCDIR=Source
HDIR=Headers
OBJ=$(patsubst %,$(OBJDIR)/%,main.o vector.o obstacle.o \
        person.o simulation.o map.o wall.o room.o )

all: CrowdSim

CrowdSim: $(OBJ)
                    $(CC) $(CFLAGS) -o $@ $^

$(OBJDIR)/%.o: $(SRCDIR)/%.cc $(HDIR)/%.h
                    $(CC) $(CFLAGS) -c -o $@ $<

clean:
            rm -rf Objects/*.o Source/*.o

When attempting to make, I receive the error: "No rule to make target 'Objects/main.o' needed by 'CrowdSim'. Note: this is my first attempt at a makefile, and I'm following the example here.

Additional information: All my .cc files are stored in Source, all my .h files are in Headers, and I want to put all my .o files in Objects.

Upvotes: 0

Views: 605

Answers (1)

MadScientist
MadScientist

Reputation: 100781

A rule like this:

$(OBJDIR)/%.o: $(SRCDIR)/%.cc $(HDIR)/%.h

requires both the prerequisites to exist. If either one does not exist, then the rule doesn't match and make will ignore it and look for another rule. In this case there is no other rule, so make fails.

If you don't always have both a .cc and .h file for every .o file, then you cannot write your rule like this.

Instead, you'll have to write the pattern rule like this:

$(OBJDIR)/%.o: $(SRCDIR)/%.cc
        $(CC) $(CFLAGS) -c -o $@ $<

Then you'll have to declare the header files separately, like this:

$(OBJDIR)/vector.o: $(HDIR)/vector.h

etc. for any headers. You might consider implementing a method to automatically manage dependencies, such as this one.

By the way, CC and CFLAGS are for C compilers. You have C++ code here. By convention in makefiles you should use CXX and CXXFLAGS for C++ compilers.

Upvotes: 1

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