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Full Discussion: Why does this example C code run and yet SHOULD either not compile or give a segmentation fault?
Top Forums Programming Why does this example C code run and yet SHOULD either not compile or give a segmentation fault? Post 303033023 by wisecracker on Thursday 28th of March 2019 03:21:04 PM
Old 03-28-2019
Apologies if this attaches to the previous post.
As a finale to this thread I decided to compile using the correct 'asm()' function __asm__ volatile() .
Code:
/* Real obfuscation scenario. */

#include <stdio.h>

int addition(int NUM1, int NUM2);
int obfuscate(int NUM1, int NUM2);

int main()
{
    int NUMBER1;
    int NUMBER2;
    int SUM;

    __asm__ volatile("nop;"
    "jmp    out;"
    "in:"
    "nop;");

    printf("Enter two integer numbers:- ");
    scanf("%d %d", &NUMBER1, &NUMBER2);

    SUM = addition(NUMBER1, NUMBER2);

    printf("SUM = %d.\n", SUM);

    return(0);
}

int addition(int NUM1,int NUM2)
{
    int RESULT;
    RESULT = NUM1 + NUM2;
    return RESULT;
}

int obfuscate(int NUM1,int NUM2)
{
    int RESULT;

    __asm__ volatile("jmp    getout;"
    "nop;"
    "out:"
    "nop;"
    "jmp    in;"
    "getout:"
    "nop;");
    /* Any number of these jimps could be used to hide stuff. */

    RESULT = NUM1 / NUM2;
    return RESULT;
}

Results, OSX 10.14.3, default bash terminal, gcc 4.2.1.
The results are similar for AMIGA OS 3.0.x gcc 2.95.3 and Linunx Mint 19 gcc 7.3.0.
Code:
Last login: Thu Mar 28 18:58:36 on console
AMIGA:amiga~> cd Desktop/Code/C
AMIGA:amiga~/Desktop/Code/C> gcc -Wall -ansi obfuscate_asm.c -o obfuscate_asm
AMIGA:amiga~/Desktop/Code/C> ./obfuscate_asm
Enter two integer numbers:- 123 456
SUM = 579.
AMIGA:amiga~/Desktop/Code/C> hexdump -C obfuscate_asm
........
00000e90  55 48 89 e5 48 83 ec 20  c7 45 fc 00 00 00 00 90  |UH..H.. .E......|
00000ea0  e9 8b 00 00 00 90 48 8d  3d cb 00 00 00 b0 00 e8  |......H.=.......|
00000eb0  92 00 00 00 48 8d 3d da  00 00 00 48 8d 75 f8 48  |....H.=....H.u.H|
00000ec0  8d 55 f4 89 45 ec b0 00  e8 7f 00 00 00 8b 7d f8  |.U..E.........}.|
00000ed0  8b 75 f4 89 45 e8 e8 25  00 00 00 48 8d 3d b9 00  |.u..E..%...H.=..|
00000ee0  00 00 89 45 f0 8b 75 f0  b0 00 e8 57 00 00 00 31  |...E..u....W...1|
00000ef0  f6 89 45 e4 89 f0 48 83  c4 20 5d c3 0f 1f 40 00  |..E...H.. ]...@.|
00000f00  55 48 89 e5 89 7d fc 89  75 f8 8b 75 fc 03 75 f8  |UH...}..u..u..u.|
00000f10  89 75 f4 8b 45 f4 5d c3  0f 1f 84 00 00 00 00 00  |.u..E.].........|
00000f20  55 48 89 e5 89 7d fc 89  75 f8 e9 07 00 00 00 90  |UH...}..u.......|
00000f30  90 e9 6f ff ff ff 90 8b  45 fc 99 f7 7d f8 89 45  |..o.....E...}..E|
00000f40  f4 8b 45 f4 5d c3 ff 25  c4 00 00 00 ff 25 c6 00  |..E.]..%.....%..|
00000f50  00 00 00 00 4c 8d 1d ad  00 00 00 41 53 ff 25 9d  |....L......AS.%.|
00000f60  00 00 00 90 68 00 00 00  00 e9 e6 ff ff ff 68 0e  |....h.........h.|
00000f70  00 00 00 e9 dc ff ff ff  45 6e 74 65 72 20 74 77  |........Enter tw|
00000f80  6f 20 69 6e 74 65 67 65  72 20 6e 75 6d 62 65 72  |o integer number|
00000f90  73 3a 2d 20 00 25 64 20  25 64 00 53 55 4d 20 3d  |s:- .%d %d.SUM =|
00000fa0  20 25 64 2e 0a 00 00 00  01 00 00 00 1c 00 00 00  | %d.............|
........
AMIGA:amiga~/Desktop/Code/C> _

Voila! No error but the jumps are still there.
 

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LEARN ABOUT DEBIAN

djvu2hocr

DJVU2HOCR(1)							 djvu2hocr manual						      DJVU2HOCR(1)

NAME

       djvu2hocr - DjVu to hOCR converter

SYNOPSIS

       djvu2hocr [option...] djvu-file

       djvu2hocr {--version | --help | -h}

DESCRIPTION

       djvu2hocr converts hidden text from a DjVu file to the hOCR[1] format.

OPTIONS

   Text segmentation options
       --word-segmentation=simple
	   Use the same word segmentation as found in the DjVu file.

	   This is the default.

       --word-segmentation=uax29
	   Use the Unicode Text Segmentation[2] algorithm to break lines into words, possibly fixing word segmentation found in the DjVu file.

   Other options
       --version
	   Output version information and exit.

       -h, --help
	   Display help and exit.

PORTABILITY

       djvu2hocr uses a custom extension to hOCR to retain characters which cannot be directly represented in an HTML/XML document. For example,
       control character BEL (^G, U+0007), is converted into the following HTML chunk: <span class="djvu_char" title="#x07"> </span>

SEE ALSO

       djvu(1)

AUTHOR

       Jakub Wilk <jwilk@jwilk.net>
	   Author.

NOTES

	1. hOCR
	   http://docs.google.com/View?docid=dfxcv4vc_67g844kf

	2. Unicode Text Segmentation
	   http://unicode.org/reports/tr29/

djvu2hocr 0.7.9 						    03/10/2012							      DJVU2HOCR(1)
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