Compilation Steps in C Program: Pre-processing, Compilation, Assemble, Linking
In this tutorial, we will learn the compilation process of the C Program in detail and understand the intermediate files generated during the compilation process.
Understanding about the Compilation?
Converting the high-level language source file into a low-level machine-readable format is called compilation. It checked the syntax and structural error of the source file and generate the object code.
Let’s start the compilation process with a simple hello world C program.
/* Learning C compilation step*/
#include<stdio.h>
int main()
{
printf("Hello World !");
return 0;
}
To Compile the above program run the below command.
$ gcc -save-temps hello.c -o hello
-save-temps flag is used to save all the intermediate files during compilation.
hello.i (Generated by Pre-processr)
hello.s (Generated by Compiler)
hello.o (Generated by Assembler)
hello (Generated by Linker)
Four Stages of Compilation Process in C Program
There are four steps to compile the c program and generate the executable binary.
Pre-processing
The first step of compilation is called preprocessing.
- Lines starting with a # are interpreted by the preprocessor
- Removal of Comments form source code
- Expansion of Macros
- Expansion of the included files
$ gcc -E hello.c -o hello.i
Compilation
The second step is called compilation.
- The preprocessed code is translated to assembly instructions.
- Verify the C program for syntax errors.
- Translate the file into intermediate code i.e. in assembly language.
$ gcc -S hello.i -o hello.s
Assembly
In this step, Assembler is used to translate the assembly instructions to object code.
$ gcc -c hello.s -o hello.o
Read the binary file by using the following commands:
$ objdump -D hello.o
$ hexdump hello.o
At this stage only existing code is converted into machine language, the function calls like printf() are not resolved.
Linking
This step links the generated object file with a standard library and generates the final executable file.
- appending bootstrap code
- linker assigned the load address to executable
- Linux executable file called .elf
- windows executable called .cof
$ gcc hello.c -o hello