Same code different characters

Question

Note: This challenge only allows answers in compiled languages

Task

Your task is pretty simple, make two different programs that when compiled result in the same output.

Scoring

Here is where the fun comes in. Your score will be the number of unique bytes present in exactly one program. For example if your two programs (encoded in IBM Code page 437) are

☻☻Program A

and

☺Program B

The characters that are in exactly one program are

☻☺AB

Thus the score is 4. Note that ☻ appears twice in the first program but is only counted once.

Your goal is to get the highest score, the highest score possible is 256.

Here is a scoring program that works for ASCII encoded programs.

Stipulations

• Every byte in both programs should be able to be replaced with a different byte causing either the program to compile into a different result or fail to compile all together. Removing any byte should do the same.

• You may use any compilation flags as long as both programs are run with the same flags.

• The resulting compilation should be static (i.e. should not vary from run to run), if results vary from machine to machine indicate the machine it is intended to run on.

• The output of compilation should be byte for byte identical not "equivalent" or "similar enough".

• The output of the compilation should be non-empty

• Warnings/Errors need not be the same between compilations

• If either the programs or the compilation include unprintable characters be sure to include a hexdump. Although it is not technically required.

Answer 1

Perl, score 254 + 2 = 256

Here's a hex dump of one program:

00000000: 6c65 6e67 7468 2700 0102 0304 0506 0708  length'.........
00000010: 090a 0b0c 0d0e 0f10 1112 1314 1516 1718  ................
00000020: 191a 1b1c 1d1e 1f20 2123 2425 2628 292a  ....... !#$%&()*
00000030: 2b2c 2d2e 2f30 3132 3334 3536 3738 393a  +,-./0123456789:
00000040: 3b3c 3d3e 3f40 4142 4344 4546 4748 494a  ;<=>?@ABCDEFGHIJ
00000050: 4b4c 4d4e 4f50 5152 5354 5556 5758 595a  KLMNOPQRSTUVWXYZ
00000060: 5b5d 5e5f 6061 6263 6465 6667 6869 6a6b  []^_`abcdefghijk
00000070: 6c6d 6e6f 7071 7273 7475 7677 7879 7a7b  lmnopqrstuvwxyz{
00000080: 7c7d 7e7f 8081 8283 8485 8687 8889 8a8b  |}~.............
00000090: 8c8d 8e8f 9091 9293 9495 9697 9899 9a9b  ................
000000a0: 9c9d 9e9f a0a1 a2a3 a4a5 a6a7 a8a9 aaab  ................
000000b0: acad aeaf b0b1 b2b3 b4b5 b6b7 b8b9 babb  ................
000000c0: bcbd bebf c0c1 c2c3 c4c5 c6c7 c8c9 cacb  ................
000000d0: cccd cecf d0d1 d2d3 d4d5 d6d7 d8d9 dadb  ................
000000e0: dcdd dedf e0e1 e2e3 e4e5 e6e7 e8e9 eaeb  ................
000000f0: eced eeef f0f1 f2f3 f4f5 f6f7 f8f9 fafb  ................
00000100: fcfd feff 273d 3d32 3533 6f72 2078 2829  ....'==253or x()

and here's the other program:

"\\"

Perl isn't normally thought of a compiled language, but it is; it's first compiled to bytecode, and then the bytecode is executed. You can apply a filter on the bytecode (e.g. to dump it rather than running the program) using the -MO option. Both these programs compile into the following bytecode (disassembled using -MO=Terse):

LISTOP (0x564fcd99f020) leave [1] 
    OP (0x564fcd99f148) enter 
    COP (0x564fcd99f068) nextstate 
    OP (0x564fcd99f100) null [5] 

Explanation

Perl replaces all statements with no effect (such as string literals on their own) with a hardcoded "statement with no effect" statement in the resulting bytecode, so both programs compile to the same thing. In terms of character replacements, replacing most of the characters from program 1 with apostrophes will cause it to fail to compile (or replacing the apostrophes with 0). In program 2, replacing the any character with c will cause the program to fail to compile (as \c takes an argument).

As for character deletions, the first version of this answer predated the "radiation hardening rule" (that deleting any character must change the behaviour of the program). This updated, radiation-hardened version works via the use of a checksum; if deleting a character doesn't outright cause a syntax error, the code will compile into a call to the nonexistent function x. The Perl compiler doesn't optimize out the call in the case where it's made (and in general doesn't seem aware that the function doesn't exist), and thus the output is different. However, Perl's constant folder is capable of seeing that the un-mutated program is a single statement with no effect, and thus optimizes the whole thing down into a single statement like before.

I originally misread the question as counting only unique characters from one program, and tried to optimize for that. Clearly, program 2 needs to contain at least one character in order to generate the "statement with no effect" opcode, meaning that the best possible score in one program is 255. I haven't yet found a way to include a backslash in program 1 in such a way that the character immediately following it can't be replaced in such a way as to cause the program to break, but it wouldn't surprise me if it were possible (leading to a score of 255 + 1 = 256).

Answer 2

C, 231

Program A

i[]={'','','','','','','',','   ','
                                       ','
                                          ','','','','','','','','','','','','','','','','','','',' ','!','"','#','$','%','&','\'','(',')','*','+',',','-','.','/','0','1','2','3','4','5','6','7','8','9',':',';','<','=','>','?','@','A','B','C','D','E','F','G','H','I','J','K','L','M','N','O','P','Q','R','S','T','U','V','W','X','Y','Z','[','\\',']','^','_','`','a','b','c','d','e','f','g','h','i','j','k','l','m','n','o','p','q','r','s','t','u','v','w','x','y','z','{','|','}','~','','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�','�'};main(){}

Lots of unprintables above. Here's the xxd hexdump:

00000000: 695b 5d3d 7b27 0127 2c27 0227 2c27 0327  i[]={'.','.','.'
00000010: 2c27 0427 2c27 0527 2c27 0627 2c27 0727  ,'.','.','.','.'
00000020: 2c27 0827 2c27 0927 2c27 0b27 2c27 0c27  ,'.','.','.','.'
00000030: 2c27 0e27 2c27 0f27 2c27 1027 2c27 1127  ,'.','.','.','.'
00000040: 2c27 1227 2c27 1327 2c27 1427 2c27 1527  ,'.','.','.','.'
00000050: 2c27 1627 2c27 1727 2c27 1827 2c27 1927  ,'.','.','.','.'
00000060: 2c27 1a27 2c27 1b27 2c27 1c27 2c27 1d27  ,'.','.','.','.'
00000070: 2c27 1e27 2c27 1f27 2c27 2027 2c27 2127  ,'.','.',' ','!'
00000080: 2c27 2227 2c27 2327 2c27 2427 2c27 2527  ,'"','#','$','%'
00000090: 2c27 2627 2c27 5c27 272c 2728 272c 2729  ,'&','\'','(',')
000000a0: 272c 272a 272c 272b 272c 272c 272c 272d  ','*','+',',','-
000000b0: 272c 272e 272c 272f 272c 2730 272c 2731  ','.','/','0','1
000000c0: 272c 2732 272c 2733 272c 2734 272c 2735  ','2','3','4','5
000000d0: 272c 2736 272c 2737 272c 2738 272c 2739  ','6','7','8','9
000000e0: 272c 273a 272c 273b 272c 273c 272c 273d  ',':',';','<','=
000000f0: 272c 273e 272c 273f 272c 2740 272c 2741  ','>','?','@','A
00000100: 272c 2742 272c 2743 272c 2744 272c 2745  ','B','C','D','E
00000110: 272c 2746 272c 2747 272c 2748 272c 2749  ','F','G','H','I
00000120: 272c 274a 272c 274b 272c 274c 272c 274d  ','J','K','L','M
00000130: 272c 274e 272c 274f 272c 2750 272c 2751  ','N','O','P','Q
00000140: 272c 2752 272c 2753 272c 2754 272c 2755  ','R','S','T','U
00000150: 272c 2756 272c 2757 272c 2758 272c 2759  ','V','W','X','Y
00000160: 272c 275a 272c 275b 272c 275c 5c27 2c27  ','Z','[','\\','
00000170: 5d27 2c27 5e27 2c27 5f27 2c27 6027 2c27  ]','^','_','`','
00000180: 6127 2c27 6227 2c27 6327 2c27 6427 2c27  a','b','c','d','
00000190: 6527 2c27 6627 2c27 6727 2c27 6827 2c27  e','f','g','h','
000001a0: 6927 2c27 6a27 2c27 6b27 2c27 6c27 2c27  i','j','k','l','
000001b0: 6d27 2c27 6e27 2c27 6f27 2c27 7027 2c27  m','n','o','p','
000001c0: 7127 2c27 7227 2c27 7327 2c27 7427 2c27  q','r','s','t','
000001d0: 7527 2c27 7627 2c27 7727 2c27 7827 2c27  u','v','w','x','
000001e0: 7927 2c27 7a27 2c27 7b27 2c27 7c27 2c27  y','z','{','|','
000001f0: 7d27 2c27 7e27 2c27 7f27 2c27 8027 2c27  }','~','.','.','
00000200: 8127 2c27 8227 2c27 8327 2c27 8427 2c27  .','.','.','.','
00000210: 8527 2c27 8627 2c27 8727 2c27 8827 2c27  .','.','.','.','
00000220: 8927 2c27 8a27 2c27 8b27 2c27 8c27 2c27  .','.','.','.','
00000230: 8d27 2c27 8e27 2c27 8f27 2c27 9027 2c27  .','.','.','.','
00000240: 9127 2c27 9227 2c27 9327 2c27 9427 2c27  .','.','.','.','
00000250: 9527 2c27 9627 2c27 9727 2c27 9827 2c27  .','.','.','.','
00000260: 9927 2c27 9a27 2c27 9b27 2c27 9c27 2c27  .','.','.','.','
00000270: 9d27 2c27 9e27 2c27 9f27 2c27 a027 2c27  .','.','.','.','
00000280: a127 2c27 a227 2c27 a327 2c27 a427 2c27  .','.','.','.','
00000290: a527 2c27 a627 2c27 a727 2c27 a827 2c27  .','.','.','.','
000002a0: a927 2c27 aa27 2c27 ab27 2c27 ac27 2c27  .','.','.','.','
000002b0: ad27 2c27 ae27 2c27 af27 2c27 b027 2c27  .','.','.','.','
000002c0: b127 2c27 b227 2c27 b327 2c27 b427 2c27  .','.','.','.','
000002d0: b527 2c27 b627 2c27 b727 2c27 b827 2c27  .','.','.','.','
000002e0: b927 2c27 ba27 2c27 bb27 2c27 bc27 2c27  .','.','.','.','
000002f0: bd27 2c27 be27 2c27 bf27 2c27 c027 2c27  .','.','.','.','
00000300: c127 2c27 c227 2c27 c327 2c27 c427 2c27  .','.','.','.','
00000310: c527 2c27 c627 2c27 c727 2c27 c827 2c27  .','.','.','.','
00000320: c927 2c27 ca27 2c27 cb27 2c27 cc27 2c27  .','.','.','.','
00000330: cd27 2c27 ce27 2c27 cf27 2c27 d027 2c27  .','.','.','.','
00000340: d127 2c27 d227 2c27 d327 2c27 d427 2c27  .','.','.','.','
00000350: d527 2c27 d627 2c27 d727 2c27 d827 2c27  .','.','.','.','
00000360: d927 2c27 da27 2c27 db27 2c27 dc27 2c27  .','.','.','.','
00000370: dd27 2c27 de27 2c27 df27 2c27 e027 2c27  .','.','.','.','
00000380: e127 2c27 e227 2c27 e327 2c27 e427 2c27  .','.','.','.','
00000390: e527 2c27 e627 2c27 e727 2c27 e827 2c27  .','.','.','.','
000003a0: e927 2c27 ea27 2c27 eb27 2c27 ec27 2c27  .','.','.','.','
000003b0: ed27 2c27 ee27 2c27 ef27 2c27 f027 2c27  .','.','.','.','
000003c0: f127 2c27 f227 2c27 f327 2c27 f427 2c27  .','.','.','.','
000003d0: f527 2c27 f627 2c27 f727 2c27 f827 2c27  .','.','.','.','
000003e0: f927 2c27 fa27 2c27 fb27 2c27 fc27 2c27  .','.','.','.','
000003f0: fd27 2c27 fe27 2c27 ff27 7d3b 6d61 696e  .','.','.'};main
00000400: 2829 7b7d 0a                             (){}.

Program B

i[]={1,2,3,4,5,6,7,010,011,013,014,016,017,020,021,022,023,024,025,026,027,030,031,032,033,034,035,036,037,040,041,042,043,044,045,046,047,050,051,052,053,054,055,056,057,060,061,062,063,064,065,066,067,070,071,072,073,074,075,076,077,0100,0101,0102,0103,0104,0105,0106,0107,0110,0111,0112,0113,0114,0115,0116,0117,0120,0121,0122,0123,0124,0125,0126,0127,0130,0131,0132,0133,0134,0135,0136,0137,0140,0141,0142,0143,0144,0145,0146,0147,0150,0151,0152,0153,0154,0155,0156,0157,0160,0161,0162,0163,0164,0165,0166,0167,0170,0171,0172,0173,0174,0175,0176,0177,-0200,-0177,-0176,-0175,-0174,-0173,-0172,-0171,-0170,-0167,-0166,-0165,-0164,-0163,-0162,-0161,-0160,-0157,-0156,-0155,-0154,-0153,-0152,-0151,-0150,-0147,-0146,-0145,-0144,-0143,-0142,-0141,-0140,-0137,-0136,-0135,-0134,-0133,-0132,-0131,-0130,-0127,-0126,-0125,-0124,-0123,-0122,-0121,-0120,-0117,-0116,-0115,-0114,-0113,-0112,-0111,-0110,-0107,-0106,-0105,-0104,-0103,-0102,-0101,-0100,-077,-076,-075,-074,-073,-072,-071,-070,-067,-066,-065,-064,-063,-062,-061,-060,-057,-056,-055,-054,-053,-052,-051,-050,-047,-046,-045,-044,-043,-042,-041,-040,-037,-036,-035,-034,-033,-032,-031,-030,-027,-026,-025,-024,-023,-022,-021,-020,-017,-016,-015,-014,-013,-012,-011,-010,-7,-6,-5,-4,-3,-2,-1};main(){}

These compile to precisely the same object code. GCC embeds the filename in the object code, so you'll need to give the files the same name (in different directories).

I was worried that the fact that there are no references to i might cause the compiler to optimize this variable out completely, but I think that making it a global guarantees that it will be present in the object. This may be verified by inspection of the generated assembly:

    .file   "diffchar.c"
    .globl  i
    .data
    .align 32
    .type   i, @object
    .size   i, 1012
i:
    .long   1
    .long   2
    .long   3
    .long   4
    .long   5
    .long   6
    .long   7
    .long   8
    .long   9
    .long   11
    .long   12
    .long   14
    .long   15
    .long   16
    .long   17
    .long   18
    .long   19
    .long   20
    .long   21
    .long   22
    .long   23
    .long   24
    .long   25
    .long   26
    .long   27
    .long   28
    .long   29
    .long   30
    .long   31
    .long   32
    .long   33
    .long   34
    .long   35
    .long   36
    .long   37
    .long   38
    .long   39
    .long   40
    .long   41
    .long   42
    .long   43
    .long   44
    .long   45
    .long   46
    .long   47
    .long   48
    .long   49
    .long   50
    .long   51
    .long   52
    .long   53
    .long   54
    .long   55
    .long   56
    .long   57
    .long   58
    .long   59
    .long   60
    .long   61
    .long   62
    .long   63
    .long   64
    .long   65
    .long   66
    .long   67
    .long   68
    .long   69
    .long   70
    .long   71
    .long   72
    .long   73
    .long   74
    .long   75
    .long   76
    .long   77
    .long   78
    .long   79
    .long   80
    .long   81
    .long   82
    .long   83
    .long   84
    .long   85
    .long   86
    .long   87
    .long   88
    .long   89
    .long   90
    .long   91
    .long   92
    .long   93
    .long   94
    .long   95
    .long   96
    .long   97
    .long   98
    .long   99
    .long   100
    .long   101
    .long   102
    .long   103
    .long   104
    .long   105
    .long   106
    .long   107
    .long   108
    .long   109
    .long   110
    .long   111
    .long   112
    .long   113
    .long   114
    .long   115
    .long   116
    .long   117
    .long   118
    .long   119
    .long   120
    .long   121
    .long   122
    .long   123
    .long   124
    .long   125
    .long   126
    .long   127
    .long   -128
    .long   -127
    .long   -126
    .long   -125
    .long   -124
    .long   -123
    .long   -122
    .long   -121
    .long   -120
    .long   -119
    .long   -118
    .long   -117
    .long   -116
    .long   -115
    .long   -114
    .long   -113
    .long   -112
    .long   -111
    .long   -110
    .long   -109
    .long   -108
    .long   -107
    .long   -106
    .long   -105
    .long   -104
    .long   -103
    .long   -102
    .long   -101
    .long   -100
    .long   -99
    .long   -98
    .long   -97
    .long   -96
    .long   -95
    .long   -94
    .long   -93
    .long   -92
    .long   -91
    .long   -90
    .long   -89
    .long   -88
    .long   -87
    .long   -86
    .long   -85
    .long   -84
    .long   -83
    .long   -82
    .long   -81
    .long   -80
    .long   -79
    .long   -78
    .long   -77
    .long   -76
    .long   -75
    .long   -74
    .long   -73
    .long   -72
    .long   -71
    .long   -70
    .long   -69
    .long   -68
    .long   -67
    .long   -66
    .long   -65
    .long   -64
    .long   -63
    .long   -62
    .long   -61
    .long   -60
    .long   -59
    .long   -58
    .long   -57
    .long   -56
    .long   -55
    .long   -54
    .long   -53
    .long   -52
    .long   -51
    .long   -50
    .long   -49
    .long   -48
    .long   -47
    .long   -46
    .long   -45
    .long   -44
    .long   -43
    .long   -42
    .long   -41
    .long   -40
    .long   -39
    .long   -38
    .long   -37
    .long   -36
    .long   -35
    .long   -34
    .long   -33
    .long   -32
    .long   -31
    .long   -30
    .long   -29
    .long   -28
    .long   -27
    .long   -26
    .long   -25
    .long   -24
    .long   -23
    .long   -22
    .long   -21
    .long   -20
    .long   -19
    .long   -18
    .long   -17
    .long   -16
    .long   -15
    .long   -14
    .long   -13
    .long   -12
    .long   -11
    .long   -10
    .long   -9
    .long   -8
    .long   -7
    .long   -6
    .long   -5
    .long   -4
    .long   -3
    .long   -2
    .long   -1
    .text
    .globl  main
    .type   main, @function
main:
.LFB0:
    .cfi_startproc
    pushq   %rbp
    .cfi_def_cfa_offset 16
    .cfi_offset 6, -16
    movq    %rsp, %rbp
    .cfi_def_cfa_register 6
    movl    $0, %eax
    popq    %rbp
    .cfi_def_cfa 7, 8
    ret
    .cfi_endproc
.LFE0:
    .size   main, .-main
    .ident  "GCC: (Ubuntu 5.4.0-6ubuntu1~16.04.4) 5.4.0 20160609"
    .section    .note.GNU-stack,"",@progbits

Note that in program B, (most of) the char values are given in octal. They could have also been given in decimal, but by using octal, we gain a couple of extra characters - 8 and 9 - in the difference set.

GCC doesn't seem to like CR, LF and (for obvious reasons) NUL characters inside of single quotes ''.

Try it online and score.

Answer 3

Python, score 16 26 27 28

Unique Characters: -+;132547698<ACBEDFOXabopsx|

Calculate the score

Program 1:

def y():
 if 0: 0xBCAFD0|0XE|(0o4<<0O4)|48;

 return 0

In program 1, there are 5 spaces in the seemingly blank line.

Program 2:

def y():
 if 0:return--12365790+(0b1110000)
 pass
 return 0

Some help was found with the peephole optimiser source code.

Tested with this helper script: Try it online!

Answer 4

Python 3.6, 2 3 5 6

Program 1:

z=11_11;a=41_68;y=None;x=5_2_7_9;x*x

Program 2:

z=1111;a=4168;y=None;x=1111+4168;x*x

Python isn't normally compiled, but it does compile its source code into pyc files. Crucially, such compiling includes an optimization pass which changes "1111+4168" into 5279. The underscores serve two purposes: one of them is to add one to the score, and the other is the keep the length, which is stored in the pyc header the same. All of the variable assignments other than 'x' are to keep the co_consts in the right order. The x*x at the end serves to keep the co_stacksize the same.

Answer 5

FASM, 254

00000000h: 64 62 20 27 01 02 03 04 05 06 07 08 0B 0C 0E 0F ; db '............
00000010h: 10 11 12 13 14 15 16 17 18 19 1B 1C 1D 1E 1F 21 ; ...............!
00000020h: 22 23 24 25 26 28 29 2A 2B 2D 2E 2F 3A 3B 3C 3D ; "#$%&()*+-./:;<=
00000030h: 3E 3F 40 41 43 45 46 47 48 49 4A 4B 4C 4D 4E 4F ; >?@ACEFGHIJKLMNO
00000040h: 50 51 52 53 54 55 56 57 58 59 5A 5B 5C 5D 5E 5F ; PQRSTUVWXYZ[\]^_
00000050h: 60 61 63 65 66 67 68 69 6A 6B 6C 6D 6E 6F 70 71 ; `acefghijklmnopq
00000060h: 72 73 74 75 76 77 78 79 7A 7B 7C 7D 7E 7F 80 81 ; 
00000070h: 82 83 84 85 86 87 88 89 8A 8B 8C 8D 8E 8F 90 91 ; 
00000080h: 92 93 94 95 96 97 98 99 9A 9B 9C 9D 9E 9F A0 A1 ; 
00000090h: A2 A3 A4 A5 A6 A7 A8 A9 AA AB AC AD AE AF B0 B1 ; 
000000a0h: B2 B3 B4 B5 B6 B7 B8 B9 BA BB BC BD BE BF C0 C1 ; 
000000b0h: C2 C3 C4 C5 C6 C7 C8 C9 CA CB CC CD CE CF D0 D1 ; 
000000c0h: D2 D3 D4 D5 D6 D7 D8 D9 DA DB DC DD DE DF E0 E1 ; 
000000d0h: E2 E3 E4 E5 E6 E7 E8 E9 EA EB EC ED EE EF F0 27 ; 
000000e0h: 0D 64 62 20 27 F1 F2 F3 F4 F5 F6 F7 F8 F9 FA FB ; 
000000f0h: FC FD FE FF 27                                  ; 

DB  1,2,3,4,5,6,7,8,11,12,14,15,16,17,18,19,20,21,22,23,24,25,27,28,29,30,31,33,34,35,36,37,38,40,41,42,43,45,46,47,58,59,60,61,62,63,64,65,67,69,70,71,72,73,74,75,76,77,78,79,80,81,82,83,84,85,86,87,88,89,90,91,92,93,94,95,96,97,99,101,102,103,104,105,106,107,108,109,110,111,112,113,114,115,116,117,118,119,120,121,122,123,124,125,126,127,128,129,130,131,132,133,134,135,136,137,138,139,140,141,142,143,144,145,146,147,148,149,150,151,152,153,154,155,156,157,158,159,160,161,162,163,164,165,166,167,168,169,170,171,172,173,174,175,176,177,178,179,180,181,182,183,184,185,186,187,188,189,190,191,192,193,194,195,196,197,198,199,200,201,202,203,204,205,206,207,208,209,210,211,212,213,214,215,216,217,218,219,220,221,222,223,224,225,226,227,228,229,230,231,232,233,234,235,236,237,238,239,240,241,242,243,244,245,246,247,248,249,250,251
DB  252,253,254,255

no 0x00 and 0x1A because fasm doesn't support the two symbols