How to export directly in a Makefile?

Question

I want to export something directly in my Makefile so I did a rule like this one :

export: export LD_LIBRARY_PATH=./smthing/here

And then I call this rule in my $(NAME)

$(NAME): $(OBJS)
        $(CXX) -o $(NAME) $(OBJS) $(CXXFLAGS) $(LDFLAGS)
        $(export)

$(OBJS) is a simple rule to convert all my .cpp into .o.

$(CXXFLAGS) are my compiling flags : -Wall -Werror -Wextra

And so on for $(LDFLAGS) you got the point..

The problem here is that my export rule is done but it didn't exported what I expected. Why ? Can you help me ?

I got this if I don't do the export by hand in my terminal :

./cutom_prog: error while loading shared libraries: custom_lib.so: cannot open shared object file: No such file or directory

Answer 1

If you want to handle exporting from Makefile, then try:

$(NAME): $(OBJS)
        @export MY_ENV_VAR=my_value; \
        $(CXX) -o $(NAME) $(OBJS) $(CXXFLAGS) $(LDFLAGS)

Exporting will only work if called in the same subshell with the command itself.

However, this solution is not going to work for LD_LIBRARY_PATH, because your intention is to update the parent process from make, which is not possible.

The workaround is to create a wrapper script that would:

• build your application by calling make
• set the LD_LIBRARY_PATH
• launch your application