Issue defining a variable at link time in Makefile - c++

Question

Ok so, im supposed to define a variable HASH_TABLE_SIZE at link time, so I would put that in my makefile.
my Makefile is as follows:
1 CC = g++
2 CFLAGS = -c -g -std=c++11 -Wall -W -Werror -pedantic -D HASH_TABLE_SIZE=10
3 LDFLAGS = -lrt
4
5 myhash : main.o hash.o hash_function.o
6 $(CC) $(LDFLAGS) main.o hash.o hash_function.o -o myhash
7
8 main.o : main.cpp hash.h
9 $(CC) $(LDFLAGS) main.cpp
10
11 hash.o : hash.cpp hash.h
12 $(CC) $(LDFLAGS) hash.cpp
13
14 hash_function.o : hash_function.cpp hash.h
15 $(CC) $(LDFLAGS) hash_function.cpp
16
17 clean :
18 rm *.o myhash
my Makefile seems correct to me, and I am putting -D HASH_TABLE_SIZE=10.
However, when I do make, I get this error:
In file included from main.cpp:3:0:
hash.h:24:27: error: 'HASH_TABLE_SIZE' was not declared in this scope
list<string> hashTable[HASH_TABLE_SIZE];
my Hash.h file is as follows:
1 /* This assignment originated at UC Riverside. The hash table size
2 should be defined at link time. Use -D HASH_TABLE_SIZE=X */
3
4 #ifndef __HASH_H
5 #define __HASH_H
6
7 #include <string>
8 #include <list>
9
10 using namespace std;
11
12 class Hash {
13
14 public:
15 Hash();
16 void remove(string word);
17 void print();
18 void processFile(string fileName);
19 bool search(string word);
20 void output(string fileName);
21 void printStats();
22
23 private:
24 list<string> hashTable[HASH_TABLE_SIZE];
25 int collisions;
26 int longestList;
27 double avgLength;
28
29 private:
30 int hf(string ins);
31 double newAvgListLen;
32
33 // put additional variables/functions below
34 // do not change anything above!
35
36 };
37
38 #endif
Why is this happening? Any help would be greatly appreciated.

Answer 1

The quick solution
You are not using CFLAGS in your recipes so it is having no effect.
It should work if you change lines 8 to 15 to:
8 main.o : main.cpp hash.h
9 $(CC) $(CFLAGS) main.cpp
10
11 hash.o : hash.cpp hash.h
12 $(CC) $(CFLAGS) hash.cpp
13
14 hash_function.o : hash_function.cpp hash.h
15 $(CC) $(CFLAGS) hash_function.cpp
Some extra details
-D is a compile time flag not a link time option.
CFLAGS is conventionally used to pass compile time flags to the compiler for a C program.
Normally CXXFLAGS would be used for a C++ program such as this and CXX to specify the C++ compiler. Make doesn't really mind though but it can make it easier to follow when conventions are used.
LDFLAGS is normally used for passing link time flags like -lrt so it only makes sense to use that on line 6, not in the compiling steps.