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Callin assembler function from C++

Callin assembler function from C++

Callin assembler function from C++


My problem is that i dont know how to call an assembler function from a C++ program. I wonder i someone can see what i have done wrong in the code below?
It is intel assembler on Linux ubuntu platform and i use the g++ compiler.

I get this error message when i link the c objectfile and the assembler file:

g++ function.s function_call.o -o function_call

function_call.o: In function `main':
function_call.cpp:(.text+0x84): undefined reference to `my_function()'

This is my code


C++ code:


extern void my_function();

int main()

Assembler code:

    .file    "function.s"

msg:    .string "Hello\n"
    len = . - msg - 1
    .align 2

.globl _my_function
    .type    _my_function, @function

    pushl   $len
    pushl   $msg
    pushl   $1
    call    write
    addl    $12, %esp    
    pushl   $0
    call    exit

    .size    main, .-main
    .size    _my_function, .-_my_function
.globl __gxx_personality_v0
    .ident    "GCC: (GNU) 4.1.3 20070929 (prerelease) (Ubuntu 4.1.2-16ubuntu2)"
    .section    .note.GNU-stack,"",@progbits

RE: Callin assembler function from C++

Perhaps you also need to disable C++ name mangling.

extern "C" void my_function();

You can also use this command,
nm function_call.o
to find out the actual name of the symbols being generated.


If you dance barefoot on the broken glass of undefined behaviour, you've got to expect the occasional cut.

RE: Callin assembler function from C++

Thanks for the hint.
Unfortunatly i still get the same error message.

RE: Callin assembler function from C++

I dont see my function when i do:
nm function_call.o

RE: Callin assembler function from C++

Now its working!
Thanks again!

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