Assembly TEST Instruction Equivalent in C ?

[Assembly] TEST Instruction Equivalent in C ? - Printable Version

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TEST Instruction Equivalent in C ? - RobotCrack - Feb 24, 2017

In need little bit help !
What

PHP Code 


<?php 
TEST 

instruction equivalent in C or Higher level language ?

* - webdev77 - Feb 24, 2017

You don't need the test instruction in higher level languages because there are better ways to write the code. It's a bitwise and operation, so you can implement that if you wish. Truly, there is no direct equivalent to my knowledge, but there are many easy ways to achieve the same result.

* - RobotCrack - Feb 24, 2017

(Feb 24, 2017 08:40 AM)webdev77 Wrote: You don't need the test instruction in higher level languages because there are better ways to write the code. It's a bitwise and operation, so you can implement that if you wish. Truly, there is no direct equivalent to my knowledge, but there are many easy ways to achieve the same result.

Thanks. Appreciate it!

* - Masm4ever - Feb 24, 2017

Code 
include \masm32\include\masm32rt.inc

.code

start:

  mov ebx, 15    ; 1+2+4+8

  .if ebx & 4

    print "test 4 succeeded", 13, 10

  .else

    print "test 4 failed", 13, 10

  .endif

  .if ebx & 16

    print "test 16 succeeded", 13, 10

  .else

    print "test 16 failed", 13, 10

  .endif

  inkey "that was easy with Masm32, right?"

  exit

end start

Output:

Code 
test 4 succeeded

test 16 failed

Now the same in C:

Code 
#include <stdio.h>

#include <conio.h>

#pragma comment(linker, "/subsystem:console" )

int main(void) {

  int ebx=15;

  if (ebx & 4)

    printf("test 4 succeeded\n");

  else

    printf("test 4 failed\n");

  if (ebx & 16)

    printf("test 16 succeeded\n");

  else

    printf("test 16 failed\n");

    _getch();

}

Some stupid brackets more but otherwise pretty much the same.

P.S.: If you prefer "pure" assembler, you can use test ebx, 4:

Code 
test ebx, 4

  .if !Zero?

    print "test 4 succeeded", 13, 10

  .else

    print "test 4 failed", 13, 10

  .endif

* - movsx - Feb 24, 2017

(Feb 24, 2017 08:32 AM)RobotCrack Wrote: In need little bit help !
What
PHP Code
<?php TEST
instruction equivalent in C or Higher level language ?

You don't need to worry about that, the compiler does.

C is modeled as an 'abstract machine'

* - electricalengineering - Feb 25, 2017

Test operation:

if ( !(me & you) ) //where me and you == 0
{

}

equivalence:

test eax, eax ; where eax is 0.
;zf = 1
je ...