CODEWITHSUNDEEP
compiler-construction
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Reputation:

Can different source code generate the same executable/binary file?

Can different source code generate the same executable/binary file?

Is this possible?

Upvotes: 3

Views: 511

Answers (3)

maykeye
maykeye

Reputation: 1316

Yes. For example

int nabs1(int a){ 
  return -abs(a); 
}

int nabs2(int a){ 
  return(a<0) ? a : -a;
}

gcc -O6 generates the same code:

 _nabs1:
pushl   %ebp
movl    %esp, %ebp
movl    8(%ebp), %edx
popl    %ebp
movl    %edx, %eax
sarl    $31, %eax
xorl    %eax, %edx
subl    %edx, %eax
ret
.p2align 4,,15
.globl _nabs2
.def    _nabs2; .scl    2;  .type   32; .endef
_nabs2:
pushl   %ebp
movl    %esp, %ebp
movl    8(%ebp), %edx
popl    %ebp
movl    %edx, %eax
sarl    $31, %eax
xorl    %eax, %edx
subl    %edx, %eax
ret

Upvotes: 4

Nosredna
Nosredna

Reputation: 86186

Yes. Compilers can make a lot of optimizations, and different source code can map to the same object code. Here are a couple trivial examples. Note that these are language-dependent.

  • You can express an integer in decimal, hex, octal, or binary--the result in the object code will be the same.
  • In many languages, the variable names do not appear in the executable, and you can change the names of variables without affecting the executable.

Upvotes: 6

James Black
James Black

Reputation: 41858

It depends on how you define similar. It would be possible to play with making tiny changes in Java or C# and have it generate to the same bytecode.

For example, in C, I expect that if I use a preprocessing command for a literal string, or use the literal string directly, that the generated code would be the same but the source was different.

Upvotes: 1

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