Programming Tricks/Questions/Trivia

[Sarevok]

---

Waaaaah... mo crash na sa Linux, command na sa fork bomb... I didn't thought nga padanganon nimo... hehe... di na ko mag paste2x ug evil Linux commands maka sala nya ko... =)

hahaha mao diay. oks ra kay virtual machine ra man to ako gigamit

karon pa ko kabantay. colon ( : ) diay ang function name ana hahaha bugoya recursive man diay

[Sarevok]

[Programming Language]
C++

[Question]
Print "Hello World!" in the console without using a semicolon

;

in your code.

[simoncpu]

[Programming Language]
C++

[Question]
Print "Hello World!" in the console without using a semicolon

;

in your code.

#include <cstdio>

int main()
{
    while (!printf("Hello world!")) { }
}

Pwede sad if statement

[cliff_drew]

OT: Bugoya sa fork bomb

[Sarevok]

[Programming Language]
C using gcc compiler

[QUESTION]
How can you make this code print gvar as 666 without editing the main function?

#include <stdio.h>

void func(void); 

int gvar = 0;

int main(void)
{
    printf("In main. gvar=%d\n", gvar);
    return 1;
}

void func(void)
{
    gvar = 666;
}

[simoncpu]

[Programming Language]
C using gcc compiler

[QUESTION]
How can you make this code print gvar as 666 without editing the main function?

#include <stdio.h>

void func(void); 

int gvar = 0;

int main(void)
{
    printf("In main. gvar=%d\n", gvar);
    return 1;
}

void func(void)
{
    gvar = 666;
}

Ladies and gentlemen, I present to you a solution that doesn't involve editing the file at all:

simoncpu@simoncpu ~ $ gcc -D'gvar=gvar=666,x' saverok.c -o saverok
simoncpu@simoncpu ~ $ ./saverok 
In main. gvar=666

This works because the preprocesssor expands the code to:

void func(void);

int gvar=666,x = 0;

int main(void)
{
    printf("In main. gvar=%d\n", gvar=666,x);
    return 1;
}

void func(void)
{
    gvar=666,x = 666;
}

[Sarevok]

Ladies and gentlemen, I present to you a solution that doesn't involve editing the file at all:

simoncpu@simoncpu ~ $ gcc -D'gvar=gvar=666,x' saverok.c -o saverok
simoncpu@simoncpu ~ $ ./saverok 
In main. gvar=666

This works because the preprocesssor expands the code to:

void func(void);

int gvar=666,x = 0;

int main(void)
{
    printf("In main. gvar=%d\n", gvar=666,x);
    return 1;
}

void func(void)
{
    gvar=666,x = 666;
}

didn't see that coming

minblown ko da hahaha unsa meaning sa -D option sa gcc? ireplace niya tanan variable or sa global variables ra na muwork?

EDIT: ahaka gitry nako sa local variable, iya man gihapon gireplace so much for security lol

[Sarevok]

nakit-an ra jud nako ang meaning. pangdebug diay

 -D name=definition
           The contents of definition are tokenized and processed as if they
           appeared during translation phase three in a #define directive.  In
           particular, the definition will be truncated by embedded newline
           characters.

           If you are invoking the preprocessor from a shell or shell-like
           program you may need to use the shell's quoting syntax to protect
           characters such as spaces that have a meaning in the shell syntax.

           If you wish to define a function-like macro on the command line, write
           its argument list with surrounding parentheses before the equals sign
           (if any).  Parentheses are meaningful to most shells, so you will need
           to quote the option.  With sh and csh, -D'name(args...)=definition'
           works.

           -D and -U options are processed in the order they are given on the
           command line.  All -imacros file and -include file options are
           processed after all -D and -U options.

[simoncpu]

Yepp, pwede ka maka-define ug macro using the command line. Bale, gi-himo nako nga macro ang "gvar" to redefine it to something else... I think ang Visual Studio pwede sad... hehe...

[Sarevok]

before ko magpost ug new question kay ako sa ipakita ang lain na answer sa ako previous question

Ichange ra nimo ang pagdeclare sa function into:

void func(void) __attribute__ ((constructor));

mangita sa ko new tricks