C & GDB Index

Hello World

C "allows to implement" or approach to various programming paradigms but due to it's characteristics it's more a procedural language. C procedural programs are divided in smaller procedures, or functions, and data or pointers to data are passed into them or is shared between them. To get started create file hello.c with;

	#include <stdio.h>

	int main() {
	    printf("Hello World!");
	    return 0;
	}

Compile;

	$ gcc -Wall hello.c -o hello

Run;

	$./hello
	Hello World!

Makefile

Make reads a Makefile by default on current directory, Makefile defines targets, for example executables and their dependencies, for example object files and source files.

Create Makefile;

	CC=gcc
	CFLAGS=-Wall

	hello: main.o hello.o

	clean:
		rm -f hello main.o hello.o

	$ touch NEWS README AUTHORS ChangeLog

Debug

To use gdb you need to compile program with -g flag. Change Makefile

	CC=gcc
	CFLAGS=-Wall -g

	hello: main.o hello.o

	clean:
		rm -f hello main.o hello.o

	$ gdb hello

Set break point;

	(gdb) break main

To start the program you can type run, this way gdb will try to run the program until the end. If program crash, gdb will stop it for debuging. Start program;

	(gdb) run

Step in next line;

	(gdb) s

Print variable "name" value;

        (gdb) print name
        $1 = 0x4005b0 "world"
        (gdb)

Print variable "name" type;

        (gdb) ptype name
        type = const char *
        (gdb)

Variable is a string constant. Execute next line to end;

	(gdb) n

C & GDB Index