CS 261 – Data Structures

C – Compilation Process

Compilation ProcessRemove CommentsReplace Pre-processor directives (#).

For example, #include gets replaced with the include file

Conditional compilation

Pre-Processor

source .h, .c

Compiler

source .h, .c

Assembler

assembly .s

Linker

machine .o

executable.exe

#include<stdio.h>

int main(void) {

printf("Hello world!\n");

}

Compilation ProcessTake resulting source code and compiles to assembly code (.s)

Machine level code that manipulates memory and processor

Pre-Processor

source .h, .c

Compiler

source .h, .c

Assembler

assembly .s

Linker

machine .o

executable.exe

.section __TEXT,__text,regular,pure_instructions.globl _main.align 4, 0x90

_main:Leh_func_begin1:

pushq %rbpLtmp0:

movq %rsp, %rbpLtmp1:

subq $16, %rspLtmp2:

movl %edi, %eaxmovl %eax, -4(%rbp)movq %rsi, -16(%rbp)leaq L_.str(%rip), %raxmovq %rax, %rdicallq _putsaddq $16, %rsppopq %rbpret

Leh_func_end1:

.section __TEXT,__cstring,cstring_literalsL_.str:

.asciz "Hello World”

gcc -g -S -Wall -std=c99 -c main.c

Compilation ProcessAssembler generates object code (.o) from the assembly code.

Object code is in binary and can’t be viewed with a text reader

Pre-Processor

source .h, .c

Compiler

source .h, .c

Assembler

assembly .s

Linker

machine .o

executable.exe

gcc –c main.c gcc – c dynArr.c

Pre-process, compile, assemble

Compilation Process The Linker pulls together your object code with libraries that you’re using in your program.

In this case, we use ‘printf’, so it will pull in the c standard libraryThe result is the executable

Pre-Processor

source .h, .c

Compiler

source .h, .c

Assembler

assembly .s

Linker

machine .o

executable.exe

#include<stdio.h>

int main(void) {

printf("Hello world!\n");

}

other libs and.o files

gcc –o prog main.o dynArr.o

Separation of Interface and Implementation

Header files (*.h) have declarations and function prototypes (ie. interfaces)

Implementation files (*.c) have implementation source

A prototype is a function signature but no body (promise that the code will be linked in later)

int max(int a, int b);/* Function prototype */

Allows us to ‘hide’ implementation in pre-compiled .o files

Function prototypes must be terminated with a semicolon.

Source Files - arrayBagStack.h

Source Files - arrayBagStack.c

.c and .h files

client’s program (.c file)

.h file 1 .h file 2

.o file with implementation

of header 1

.o file with implementation

of header 2

your data structure headers (.h)

your data structure code (.o)

not visible to client developer

visible to client developer

linker pulls in the promised code

Tips: Ensuring Declarations Seen only Once

/* Header file for foo.h */

#ifndef BIG_COMPLEX_NAME

#define BIG_COMPLEX_NAME

…

/* Rest of foo.h file. */

#endif

If foo.h is included more than once (e.g., through other included files), it only gets inserted into the source (.c) file once

Conditionallycompiled code!!!

GCC And Make

Also, see the class website for much more on gcc, make and c-programming in general

Managing Projects with make, 2nd EditionThe Power of GNU make for Building AnythingBy Andy Oram, Steve TalbottPublisher: O'Reilly MediaReleased: October 1991Pages: 168