[SOLVED] GNU Make: Using % in a pattern-rule macro

SexyBachelor · 06-02-2012, 08:38 AM

Hi,

I'm revising my code to make it a bit cleaner and right now I'm working on the makefile.

I'm having a problem with defining a pattern rule that uses % to access another variable.

Code:

# program output name
OUT=a.out

# compiler flags
FLAGS=-ggdb -std=c++0x

# library dependencies
LIBS=-lSDL -lSDL_image -lboost_system -lboost_chrono -lGL

# where to store built objects
BIN=bin

# The objects to build
OBJECTS=Geometry.o Enemy.o Surface.o Player.o SDLWindow.o Path.o Territory.o Board.o Diminisher.o Main.o

# Header Dependencies per object
Geometry_H=Geometry.h
Enemy_H=Enemy.h $(Geometry_H)
Surface_H=Surface.h $(Geometry_H)
Player_H=Player.h $(Geometry_H) $(Surface_H)
SDLWindow_H=SDLWindow.h $(Surface_H)
Path_H=Path.h $(Geometry_H)
Territory_H=Territory.h $(Geometry_H)
Board_H=Board.h $(Territory_H) $(Geometry_H) $(Player_H) $(Path_H) $(Enemy_H)
Diminisher_H=Diminisher.h $(SDLWindow_H) $(Geometry_H) $(Surface_H) $(Board_H)
Main_H=$(Diminisher_H)

# make program
default: $(BIN) $(addprefix $(BIN)/, $(OBJECTS))
    g++ -o $(OUT) $(FLAGS) $(addprefix $(BIN)/, $(OBJECTS)) $(LIBS)

# create object bin directory
$(BIN):
    @ if [ ! -d "./$(BIN)" ]; then \
        mkdir $(BIN); \
    fi
    @echo "mkdir $(BIN)"

# command to make an object
$(BIN)/%.o: %.cpp $(%_H)
    g++ -o $@ $(FLAGS) -c $<

# delete all objects and program
clean:
    rm -rf $(BIN) 
    rm -f $(OUT)

Previously I had all the make rules explicitly written out. For example, Geometry read:

Code:

$(BIN)/Geometry.o: Geometry.cpp $(Geometry_H)
    g++ -o $@ $(FLAGS) -c $<

The problem I'm having is in bold.

In the new code, $(%_H) isn't expanding to Geometry_H.
I've tried many other variants such as:
$($%_H)
$( $(value %)_H )

I'm hoping someone knows the correct syntax.

The project will still build with this code, but if I edit a header file and run make without cleaning first, make will not rebuild the objects that depend on this header as defined by the *_H variables.

The old code would rebuild the targets that depended on the edited header.

pan64 · 06-02-2012, 08:53 AM

the solution could be the target dependent macro, but it will not simplify:

Code:

$(BIN)/targetfile.o := DEP = $(target_H)
...

$(BIN)/%.o: %.cpp $(DEP) $(BIN)
    g++ -o $@ $(FLAGS) -c $<

and do not foget to add the dependency for $(BIN)

SexyBachelor · 06-02-2012, 01:51 PM

Quote:

Originally Posted by pan64

the solution could be the target dependent macro, but it will not simplify:

Code:

$(BIN)/targetfile.o := DEP = $(target_H)
...

$(BIN)/%.o: %.cpp $(DEP) $(BIN)
    g++ -o $@ $(FLAGS) -c $<

and do not foget to add the dependency for $(BIN)

I'm confused by your code (RED).
why is there a variable called "bin/targetfile.o" being assigned to it's header definition (target_h)?

Then bin/targetfile.o, DEP, and target_h would all hold the same information.

But not only that, it still doesn't solve the issue of the % not resolving inside of the variable call in the dependecy list $(%_H).

With the code in red, being that DEP is defined to only one of the header variables, you would be saying that all the objects depend on that one header. Each object (Enemy.o, Player.o, Path.o) has it's own header variable (Enemy_H, Player_H, Path_H) and I'm just trying to figure a way for % which holds the current object's stem (Enemy, Player, Path) to turn into it's corrisponding header variable (Enemy_H,...).

Unless you're suggesting that I define DEP multiple times for every Object... but I might as well just leave the code how it used to be with each object's name typed explicitly (Enemy.o: Enemy.cpp $(Enemey_H)).

If I'm not understanding what you said correctly, please reiterate.

pan64 · 06-03-2012, 04:33 AM

sorry, I was not really clear I think, so here is a link: Computed Variable Names
Originally I was thinking about target specific macros, but probably the computed variables are the better choice.