Program: Fortran module dependency analyzer and topologic build order printer.

Usage:
    -d DIRS   Comma-separated list of directories to scan non-recursively.
    -D DIRS   Comma-separated list of directories to scan recursively.
    -m        Print a Makefile dependency list instead of build order.
    -h        Show this help message.

Description:
    Scans .f90 files in given directories to detect Fortran modules and their
    'use' dependencies, then computes a topologic order for building modules.
    Can output either the ordered list of files to build or a Makefile
    dependency list suitable for build systems.

Notes:
    - Repeated use of -d or -D flags is an error.
    - Directories in the flags are comma-separated and will be scanned in the order given
    - If neither -d nor -D is specified, defaults to scanning 'src' non-recursively.

Author:
    Drake Gates

# Example makefile to use this progam for all FORTRAN projects
# Compiler and flags
FF = gfortran
FFLAGS = -cpp -fno-align-commons -O3 -ffpe-trap=zero,invalid,underflow,overflow \
         -std=legacy -ffixed-line-length-none -fall-intrinsics \
         -Wno-unused-variable -Wno-unused-function -Wno-conversion -fopenmp
FMOD = -Jmod -Imod
PROGRAM = program

# Directories
SRC_DIR = src
OBJ_DIR = obj
MOD_DIR = mod

# Topologically sorted module sources looking recursively through a source directory
TOPOLOGIC_SRC = $(shell maketopologicf90 -D $(SRC_DIR))

# Corresponding object files
OBJECTS = $(patsubst $(SRC_DIR)/%.f90, $(OBJ_DIR)/%.o, \
          $(patsubst $(SRC_DIR)/%.for, $(OBJ_DIR)/%.o, $(TOPOLOGIC_SRC)))

# Link target
all: $(PROGRAM)

# Build the program
$(PROGRAM): $(OBJECTS)
	$(FF) $(FFLAGS) -o $@ $^

# Generic pattern rule for both .f90 and .for files
$(OBJ_DIR)/%.o: $(SRC_DIR)/%.f90
	@mkdir -p $(dir $@) $(MOD_DIR)
	$(FF) $(FFLAGS) $(FMOD) -c $< -o $@

$(OBJ_DIR)/%.o: $(SRC_DIR)/%.for
	@mkdir -p $(dir $@) $(MOD_DIR)
	$(FF) $(FFLAGS) $(FMOD) -c $< -o $@

# Clean rule
clean:
	rm -rf $(OBJ_DIR)/*.o $(MOD_DIR)/*.mod $(PROGRAM)

FF = gfortran
FFLAGS = -cpp -fno-align-commons -O3 -ffpe-trap=zero,invalid,underflow,overflow \
         -std=legacy -ffixed-line-length-none -fall-intrinsics \
         -Wno-unused-variable -Wno-unused-function -Wno-conversion -fopenmp
FMOD = -Jmod -Imod
PROGRAM = some_program

LIB     = lib/some_library.a
SRC_DIR = src
OBJ_DIR = obj
MOD_DIR = mod

TOPOLOGIC_SRC = $(shell maketopologicf90 -D $(SRC_DIR))

OBJECTS = $(foreach src,$(TOPOLOGIC_SRC),$(OBJ_DIR)/$(basename $(notdir $(src))).o)

all: $(PROGRAM)

#Build the program
$(PROGRAM): $(OBJECTS)
	$(FF) $(FFLAGS) -o $@ $^ $(LIB)

obj/%.o: src/%.f90
	@mkdir -p obj mod
	$(FF) $(FFLAGS) $(FMOD) -c $< -o $@

obj/%.o: src/%.for
	@mkdir -p obj mod
	$(FF) $(FFLAGS) $(FMOD) -c $< -o $@

clean:
	rm -f obj/*.o mod/*.mod $(PROGRAM)