- The process to
translate
a C program into
an executable program
is structured as
follows:
There are 3 stages of processing when a C program is compiled:
- Unique to
the C/C++ language,
the first stage of
processing is
the C-preprocessor
- the C-preprocessor provide a sophisticated text re-writing system that allow the C program to be adapted to different computer platforms
The output of the C preprocessor is an "enriched" C program source that is generated from the original C program according to some specific parameters specified by the programmer
- The 2nd stage is
the C compiler that
translate the
"enriched" C program source into
assembler code
- The 3rd and final stage is the assembler that translate the assembler source into executable machine code
- Unique to
the C/C++ language,
the first stage of
processing is
the C-preprocessor
- We can control the
C program compilation process using
options given to the
C compile (gcc):
- gcc -E
option will
stop the
compilation process after the
C-preprocessor is
finished
- The output of the C-preprocessor is sent to the terminal
- gcc -S
option will
stop the
compilation process after the
C-compiler is
finished
- The output of the C-compiler is write to the programName.s (.s for aSsembler file)
- gcc -c
option will
stop the
compilation process after the
assembler is
finished
- The output of the assembler is written to the programName.o (.o for Object file)
- gcc -E
option will
stop the
compilation process after the
C-preprocessor is
finished
- Before invoking the
C compiler, the
C programming language system
will always invoke a
- C pre-processor
to process the program source code.
- Tasks performed by
the C pre-processor:
- Removes
comments from the source code
/* .......... */ or: // ........
- Process
macro (symbolic) definitions
#define ... ....
- Read in
included file
#include <stdio.h> or #include "header.h"
- Other
advanced
conditionals:
#ifdef ... .... #endif
#ifndef .... .... #endif
We will discuss these pre-processor "directives" in more details in the next few webpage.
- Removes
comments from the source code