Compilation process

Lecture-1

Compilation process

C Compilation process

Preprocessor

Compiler

Assember

Linker

Components of Compiler

Assembly code

Object code Libraries

Source code( .c file)

Executable file

Preprocessor

Preprocessor

/* this is demo */#include<stdio.h>void main(){ printf (“hello”);}

code of stdio.h filevoid main(){ printf (“hello”);}Preprocessor remove comments and include

header files in source code, replace macro name with code.

Compiler

Compiler

code of stdio.h filevoid main(){ printf (“hello”);}

push ebpmov ebp, espand esp, -16sub esp, 16mov eax, OFFSET FLAT:.LC0mov DWORD PTR [esp], eaxcall printfleaveret

Compiler generate assebmly code.

Assembler

Assembler

Assebler convert assemble code into object code.

push ebpmov ebp, espand esp, -16sub esp, 16mov eax, OFFSET FLAT:.LC0mov DWORD PTR [esp], eaxcall printfleaveret

001010011001010011010111101010010101010010101011010010101010100101010100110011111110010001010010101001010111110111111111111101000000001110010010

Linker

Linker

0010100110010100110101111010100101010100101010110

0010100110010100110101111010100101010100101010110

0010100110010100110101111010100101010100101010110

Libraries

Linker: Static linking

Linker

001010011001010011010111110

Libraries

001010011001010011010111110

Call function one()

#include<stdio.h>void main(){ one(); }

01010100000101001010

one()

01010100000101001010

Code of function one included in final executable file.

Linker: Static Linking

Linker

Object file1

Object file2

Libraries

Code of file 1 calling 200 funtions.Code of file 2 calling 100 functions.

Size ?

Linker:Static Linking exe file generated.1

User take exe file.2

Some changes made in one function.

3

Libraries010100

Again compilation needed so that exe file include updated one function.

4

Linker: Dynamic linking

Linker

001010011001010011010111110

Libraries

001010011001010011010111110Address of one function in memory

Call function one()

#include<stdio.h>void main(){ one(); }

01010100000101001010

one()

Memory address, where one function is loaded , included in final executable file.

Memory

0x2EA126One functionLibrary

Linker: Dynamic Linking Benefits over static linking

Size No need to compile

Library Static Library

Windows .lib (Library) Linux .a (Archive)

Dynamic Library Windows .dll (Dynamic link library) Linux .so (Shared object)

Commands Linux (gcc)

Preprocessor step ( gcc -E <filename>) Compiler step( gcc -S <filename>) Generate Object code(gcc -O <filename>) Generate executable (gcc <object code>)