Makefile directories error - c++

Question

Im using this code in the makefile, all is going good but the last line.
My code folder looks like this:
Project/bin -> For executable files
Project/build -> For .o files
Project/include -> For .hpp files
Project/src -> For .cpp files
Makefile path: Project/Makefile
# Compiler #
CC = g++
DEBUG = -g
LFLAGS =
CFLAGS = -Wall
# Directories #
SRCDIR = src/
INCDIR = include/
BUILDDIR = build/
BINDIR = bin/
# Objects #
OBJ_NAMES = main.o dfa.o dfaException.o state.o
OBJS = $(addprefix $(BUILDDIR), $(OBJ_NAMES))
# Output #
TARGET = $(BINDIR)pract3
$(TARGET): $(OBJS)
$(CC) $(CCFLAGS) $(LFLAGS) $(OBJS) -o $(TARGET)
$(BUILDDIR)%.o: $(SRCDIR)%.cpp
$(CC) $(CCFLAGS) $(LFLAGS) -c $< -o $(BUILDDIR)$($(notdir $<):.cpp=.o)
The problem is in "$(BUILDDIR)$($(notdir $<):.cpp=.o)". What Im trying to do here is:
$< contains "src/mysrc.cpp" so with $(notdir $<) I get
"mysrc.cpp"
Now, I want to change the file extension to .o, so I use $($(notdir $<):.cpp=.o) And I should get "mysrc.o". But this part is not working:
g++ -c src/main.cpp -o build/
Assembler messages:
Fatal error: can't create build/: Permission denied
Makefile:25: recipe for target 'build/main.o' failed
make: *** [build/main.o] Error 1
I use $(BUILDDIR) To get "build/mysrc.o"
Why does $($(notdir $<):.cpp=.o) somehow delete the file name ?
And now that Im here. I've learned to use make some days ago. Is there something that I should improve here ?

Answer 1

$(notdir) operates on strings.
$(X:Y=Z) operates on the value of the X variable.
So follow your expansions when $< is src/mysrc.cpp
$($(notdir $<):.cpp=.o)
becomes
$(mysrc.cpp:.cpp=.o)
Is that how you would write that?
No, you would write $(<:.cpp=.o).
So invert your operations.
$(notdir $(<:.cpp=.o))
Or, even better and simpler than that just use $# since that's the target you are building and what you want to create.
$(CC) $(CCFLAGS) $(LFLAGS) -c $< -o $#