How to view the machine language of a compiled c++ file?

Question

I wrote a simple c++ program that prints "Hello World!"

#include <iostream>
using namespace std;
int main(){
cout<<"Hello World!\n";
}

I then compiled it using g++

$ g++ Desktop/sample.cpp -o Desktop/hello

How would I be able to view the machine language, is it just

$ less Desktop/hello

?

I'm just curious to see what "machine language" looks like. Here's a sample from the above command

C>^D<A1><F4><9E>^D^H<83><F8><FF>t^S<BB><F4><9E>^D^Hf<90><83><EB>^D<FF>Ћ^C<83><F8><FF>u<F4><83><C4>^D[]Ð<90>U
<89><E5>S<83><EC>^D<E8>^@^@^@^@[<81>Ì^X^@^@<E8><<FE><FF><FF>Y[<C9><C3>^C^@^@^@^A^@^B^@Hello World!
^@^@^@^AESC^C; ^@^@^@^C^@^@^@<A4><FE><FF><FF>@^@^@^@<C8><FE><FF><FF>\^@^@^@^H<FF><FF><FF>x^@^

http://stackoverflow.com/questions/137038/how-do-you-get-assembler-output-from-c-c-source-in-gcc — Captain Giraffe, Oct 26 '11 at 15:25
You want a [Hex Editor](http://en.wikipedia.org/wiki/Hex_editor) — Benjamin Lindley, Oct 26 '11 at 15:28
I'm confused. I thought machine language is NOT assembly language. Machine language is a lower level language that's read by the hardware. http://www.webopedia.com/TERM/M/machine_language.html. Is machine language assembly language? — user784637, Oct 26 '11 at 15:30
@Led: No, it's not. I don't know why everyone is talking about assembly language. — Benjamin Lindley, Oct 26 '11 at 15:31
You could regard the assembly as being the human-readable form of what you are looking at with less. — Captain Giraffe, Oct 26 '11 at 15:32
Benjamin LOL!!! Yeah but I appreciate the context of brining assembly in. — user784637, Oct 26 '11 at 15:35

score 9 · Accepted Answer · answered Oct 26 '11 at 15:27

9

If you compile with the -S option, it will spit out the assembler output and stop. Make sure you use the -o option to set the output file to sample.s:

g++ -S -o sample.s sample.cpp

answered Oct 26 '11 at 15:27

trojanfoe

120,358
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score 5 · Answer 2 · answered Oct 26 '11 at 15:28

5

You need to compile it this way:

  g++ -g -c -Wa,-alh Desktop/sample.cpp -o Desktop/hello

The look at the assembler code with:

 objdump -d Desktop/hello

answered Oct 26 '11 at 15:28

tune2fs

7,605
5
41
57

`$ g++ -v` `gcc version 4.4.3 (Ubuntu 4.4.3-4ubuntu5)` I'm using 32bit ubuntu – user784637 Oct 26 '11 at 15:34
I tried it also on ubuntu with g++ 4.6.1 and it worked. I do not have g++ 4.4 available, so I cannot try it out. – tune2fs Oct 26 '11 at 15:38

score 1 · Answer 3 · answered Oct 26 '11 at 16:15

1

Use xxd on the binary generated by g++ to view the machine code. Assembly is an abstract version of machine code and is not neccessarily what you are looking for.

answered Oct 26 '11 at 16:15

Swiss

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score 0 · Answer 4 · answered Jan 03 '14 at 03:50

0

Use xxd -g 1 hello | more to view the binary content of the executable file 'hello' or any binary file you want to check.

answered Jan 03 '14 at 03:50

pengw

61
5

How to view the machine language of a compiled c++ file?

4 Answers4