CODEWITHSUNDEEP
c++assemblydisassembly
Geek
Geek

Reputation: 23419

How can I see the assembly code for a C++ program?

How can I see the assembly code for a C++ program?

What are the popular tools to do this?

Upvotes: 159

Views: 129020

Answers (14)

Employed Russian
Employed Russian

Reputation: 213526

Ask the compiler

If you are building the program yourself, you can ask your compiler to emit assembly source. For most UNIX compilers use the -S switch.

  • If you are using the GNU assembler, compiling with -g -Wa,-alh will give intermixed source and assembly on stdout (-Wa asks compiler driver to pass options to assembler, -al turns on assembly listing, and -ah adds "high-level source" listing):

    g++ -g -c -Wa,-alh foo.cc

  • For Visual Studio, use /FAsc.

Peek into a binary

If you have a compiled binary,

Use your debugger

Debuggers could also show disassembly.

  • Use disas command in GDB.
    Use set disassembly-flavor intel if you prefer Intel syntax.
  • or the disassembly window of Visual Studio on Windows.

Upvotes: 197

Carlo Wood
Carlo Wood

Reputation: 6791

This site is currently working for me (2017): https://godbolt.org/

Upvotes: 15

Gomes J. A.
Gomes J. A.

Reputation: 1475

You can also try this site: http://assembly.ynh.io/

There, you can paste your C or C++ code and press a blue button to see the assembly equivalent version.

Upvotes: 3

Pieter
Pieter

Reputation: 32765

If you're an Eclipse user, you can use the Disassembly view.

The Disassembly view shows the loaded program as assembler instructions mixed with source code for comparison. The currently executing line is indicated by an arrow marker and highlighted in the view. You can do the following tasks in the Disassembly view:

  • Set breakpoints at the start of any assembler instruction
  • Enable and disable breakpoints and their set their properties
  • Step through the disassembly instructions of your program
  • Jump to specific instructions in the program

Upvotes: 0

gibertoni
gibertoni

Reputation: 1378

On an Intel Mac OS X 10.8 (Mountain Lion) the -masm=intel directive didn't work. However, if you have Xcode installed, it should have installed the tool named 'otool':

otool code.o -tV

You have to provide the compiled object code as a parameter.

Upvotes: 1

Adam Markowitz
Adam Markowitz

Reputation: 13117

Whatever debugger you're using should have an assembly view (Visual Studio, Borland IDE, gdb, etc.). If you are not using a debugger and you merely want to see what assembly is in a program, you can use a disassembler or alternatively, run the program and attach to it with a debugger and do the dump from there. See references to disassemblers for information on options.

Upvotes: 6

osgx
osgx

Reputation: 94225

For gcc/g++

gcc -save-temps -fverbose-asm prog.c

This will generate prog.s with some comments on variables used in every asm line:

    movl    $42, -24(%ebp)  #, readme
    movl    -16(%ebp), %eax # pid, pid
    movl    %eax, 4(%esp)   # pid,
    movl    $.LC0, (%esp)   #,
    call    printf  #

Upvotes: 16

Wylder
Wylder

Reputation: 287

PE Explorer Disassembler for 32-bit PE files. IDA for others.

Upvotes: 4

Zifre
Zifre

Reputation: 26998

In GCC/G++, compile with -S. That will output a something.s file with the assembly code.

Edit: If you want the output to be in Intel syntax (which is IMO, much more readable, and most assembly tutorials use it), compile with -masm=intel.

Upvotes: 39

Bastien Léonard
Bastien Léonard

Reputation: 61713

Lots of people already told how to emit assembly code with a given compiler. Another solution is to compile an object file and dump it with a tool such objdump, readelf (on Unix) or DUMPBIN(link) (on Windows). You can also dump an executable, but it will be more difficult to read the output.

This has the advantage of working the same way with any compiler.

Upvotes: 6

Cătălin Pitiș
Cătălin Pitiș

Reputation: 14341

In Visual Studio you can generate the assembler listing for a C++ project.

Go to project properties, then to C++/Output Files and set Assembler Output setting and ASM list location to a file name.

Upvotes: 2

Nik
Nik

Reputation: 1364

Most compilers have an option to output an assembly listing. E.g. with VisualStudio you can use something like:

cl.exe /FAfile.asm file.c

For best readability though, most debuggers will offer a view that interleaves the disassembly with the original source, so you can compare your code with the compiler's output line by line.

Upvotes: 5

Viktor Sehr
Viktor Sehr

Reputation: 13099

In Visual Studio;

  1. set a breakpoint
  2. run the program until it stops at the breakpoint
  3. rightclick on the sourcecode and pick "show dissasembly"

Upvotes: 25

Ori Pessach
Ori Pessach

Reputation: 6833

As someone else mentioned, your platform's debugger is a good starting point. For the jackhammer of all debuggers and disassemblers, take a look at IDA Pro.

On Unix/Linux platforms (including Cygwin) you can use objdump --disassemble <executable>.

Upvotes: 5

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