1023  cd preprocessor

# webserver.c is an example of including a .h file
 1024  cd webserver_demos
 1025  vim list.c
 1026  vim list.h 
 1027  vim webserver.c 
 1028  gcc -E webserver.c | less
 1029  gcc -std=c11 webserver.c    # ERROR: missing definitions of list functions
 1037  gcc -std=c11 webserver.c list.c  # provide compiler the list functions
 1038  ./a.out 

# webserver2.c uses predefined macros
 1039  vim webserver2.c 
 1040  gcc -E webserver2.c | grep LOG
 1041  gcc -std=c11 webserver2.c list.c
 1042  ./a.out 

# macro example that can use types as parameters
 1045  cd ../parameterized_macros
 1046  vim new_macro.c 
 1046  gcc -E new_macro.c

# macro example for writing definitions automatically
 1047  vim struct_macro.c 
 1048  gcc -E struct_macro.c 


# Below is an example of conditional compilation
 1055  cd ../webserver_demos
 1056  vim webserver3.c 
 1057  vim web_utilities.h 

## This command shows that the preprocessed webserver3.c will include list.h twice
## slide 15 shows a graph of why.
 1060  gcc -E webserver3.c | grep -A3 "typedef struct List"
 ## Uncomment the header and footer guards in list.h
## Now the command shows the preprocessed webserver3.c includes list.h just once
 1062  gcc -E webserver3.c | grep -A3 "typedef struct List"
 1066  history > lec16.history