Creating a makefile for 3 files C++

[connorschwing]

Hello

I have 3 files

driver.cpp
hashtable.h
hashtable.hpp

hashtable.h has .hpp included. The driver.cpp has the header file included.

How can I make the MOST barebones makefile possible?

I just need it to generate an exectuable hash.x that i can run.

Im looking for something in the general format of

target: things
commands
link?:
commands
clean:
rm *.x *.o

I just dont know exactly what to type to make this work :(

[mbozzi]

The driver.cpp has the header file included.

Which header file? (Both `.hpp' and `.h' are often used for header files.)
I'm assuming some things about your files since I don't know about the difference between .h and .hpp files.

hash.x: driver.cpp hashtable.h hashtable.hpp
  $(CXX) $(OUTPUT_OPTION) $(CXXFLAGS) driver.cpp

should be sufficient. You will need to replace the two spaces of indentation with a SINGLE TAB CHARACTER; you must use a tab.

I'll leave this here: it's a pain in the ass to have to update the makefile every time you add an #include, change the name, or add a file. This can be automated. The alternative is having to do clean builds all the time, since you'll invariably forget to add some header file as a dependency of some source file.

Edit:
you want a clean target, too; yours is fine, with two exceptions -- we want to ignore errors, and clean is not a file we can create. Replace the indentation with a tab.

.PHONY: clean
clean:
  -rm *.x *.o

[connorschwing]

My issue is that every time I try to compile, I get a massive amount of errors basically all of the form

"error: shadows template parm 'class V' "
or
"error: declaration of 'class V'

Even though I have my #ifndef and everything, I have my endif,
and there are NO double declarations of templates anywhere, so I assumed it would be a linkage error, and this new makefile does not seem to fix that. Am I on the right track to solve this?

[mbozzi]

No, that's a compilation error.
If it was a linker error, that should have been reported in the message as coming from LD or whatever your linker's name is (I'm assuming you're using the GNU toolchain; that wasn't specified).

Here is one situation which can cause this issue:

template <typename V>
struct A { template <typename V> void foo() {}; };

We will be able to help much more effectively if you post some code.

[connorschwing]

Okay. I have a struct in my class but I avoided that situation specifically. The class is structured like this

#ifndef HASHTABLE_H
#define HASHTABLE_H

namespace cXXXXX;

{


template <typename K, typename V>
class HashTable
{
public:

// just functions that take K and V in parameters, no template definitions

private:

std::vector <std::list<std::pair<K, V>>> listVector;

size_t hash(const K &k) const;
void setPrimes(std::vector<unsigned long> &);

struct Node
{
K key;
V value;
Node* next;

Node() : next(NULL){
this->key = key;
this->value = value;

};

};

#include "hashtable.hpp"
}

#endif


The .hpp file that is linked to it is just full of functions formatted as

template< typename K , typname V>
function {
}

and produces errors on the every function on the template line

[mbozzi]

You really should show the code that actually produces the errors. It will get you better answers.

Regardless, this is enough for me to have a guess at the problem:
Hashtable.hpp contains template member function implementations. Normally these files end in a tpp, ipp, or similar extension, but that's besides the point.

Specifically, I guess your .hpp file contains code like:

template <typename K, typename V> void HashTable<K, V>::some_function(K) { blah };

The use of and K of V shadow the Hashtable's template parameters. some_function should not be declared as a template member function, because it isn't one. K and V are already visible.

Try instead something like

void HashTable::some_function(K) { whatever }

[connorschwing]

Yes, I apologize I should have included that. But yes you are exactly right about the format of the hpp file. The problem is it was given to me and I am not supposed to edit the function definitions, So I was hoping the problem was elsewhere

[mbozzi]

If you can edit hashtable.h, you can change the name of the class template parameters (e.g., to T and U) to get it to compile, and the declarations to reflect the fact that they are template member functions.

That's certainly not the best solution, but it's possibly workable.

[kbw]

Mininal makefile for that? No makefile at all. Sumply type:

make driver

Maybe we could add the header file dependencies and a default target for a more reasonable minimal makefile.

PROG = driver
SRCS = driver.cpp

all: $(PROG)

$(PROG): $(SRCS.cpp=.o) hashtable.h hashtable.hpp
    $(LINK.cc) $^ -o $@ $(LDFLAGS)

[mbozzi]

OP wanted the result to be named "hash.x", not "driver".
I don't think there is a way to do that using only implicit rules.

Also (at least in GNU Make) the first target to appear is the default, and "all" should probably be marked as a .PHONY target just in case there happens to be a file named "all" in the CWD.

Assuming G++ or Clang, we can make it more general:

CXXFLAGS += -MT $@ -MP -MMD -MF $(@:.o=.d)
hash.x: $(patsubst %.cpp,%.o,$(wildcard *.cpp))
	$(LINK.cc) $(OUTPUT_OPTION) $^
-include $(patsubst %.cpp,%.d,$(wildcard *.cpp))

[connorschwing]

Man make files are so confusing. I've never seen them written like that. I've always seen them written something like this (credit Bob Myers, FSU)

frac: main.o frac.o
g++ -o frac main.o frac.o

main.o: main.cpp frac.h
g++ -c main.cpp

frac.o: frac.cpp frac.h
g++ -c frac.cpp

clean:
rm *.o frac