COP 3223H meeting -*- Outline -*-

* Compilation with multiple modules in C

** typical homework problem example
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     TYPICAL HOMEWORK PROBLEM MODULES

Suppose you are to write function f.
We provide all files except f.c
(where you put the code for f)

Modules:
   tap.c with header tap.h
   f.c with header f.h
   test_f.c

Compilation command:

   gcc -Wall -pedantic tap.c f.c test_f.c -o test_f

 Compilation works in stages:
  1. compiling each module (gcc -c *.c)
      tap.c    -> tap.o
      f.c      -> f.o
      test_f.c -> test_f.o
  2. loading/linking (gcc *.o -o test_f)
      tap.o f.o test_f.o  ->  test_f.exe

During step 1 the compiler


During step 2 the loader/linker


Running the program:

    > ./test_f

  runs test_f.exe on Windows
       test_f on Unix/MacOS
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        ... checks each individual file (type checking, etc.)

        ... checks consistency between all cross references among files
                (also a kind of type checking)

** declarations and scope issues
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 DECLARATIONS AND SCOPE FOR FUNCTIONS in C

A function declaration

    extern double f(int x);

A function declaration and definition

    double f(int x) { return x*2.0; }

Scope of a declaration extends





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        from the point of declaration through the rest of the
        block/file in which the declaration occurs