gcc name mangling

gcc name mangling

[y2bismil]

Hi all,

I'm experimenting a bit trying to do some basic mixing between gcc and assembler.
Maybe this should all be manual work, but I'm inclined to think GCC its my setup
that's a problem.

Basically, to start, I want to call an assembler function from GCC.  

i'm just getting link errors.  the linker claims it cannot find _writechar in
main.o.  Now, its pretty easy to fix it...I need to use "_writechar" in my asm
file instead of writechar.  But, is there another way to use the name variable
name without the underscore?  Something so GCC won't mangle the name at all?  Or
something to add the the assembler file to 'export function' names differently.

Thanks for any advice.

Yamin

************************************
ASM FILE

.globl write_char


.data 
 message:
         .string "Hello, world\n" 
 .text 
 .global write_char
 write_char:
         ...some code that's incomplete
         ret 
**************************************
main.cpp

#include <iostream>

void testfunc();
extern "C"
{
   extern void write_char(char);
}

int main()
{
    std::printf("i am running now\n");
    write_char('B');
    std::printf("i did run\n");
    return 0;
}

*****************************************



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Re: gcc name mangling

[Eljay Love-Jensen]

Hi Yamin,

Checkout the -fleading-underscore / -fno-leading-underscore flag.

Note:  this is a powerful flag, since it has sweeping effects.

HTH,
--Eljay

Re: gcc name mangling

[y2bismil]

Okay, 
reading the description, it seems to make a big deal of not being binary
compatible with code not compiled with this option.

Perhaps the best solution would be to simply prepend all assembler names with
underscores?

Anyone have any experience with using gAS and GCC together.  What is the common
practice?  I hope I'm not imagining, but I did some work using gcc and external
assembler (s files), using the m68k.  I don't recall name mangling being an issue.

Yamin

Quoting Eljay Love-Jensen <eljay@adobe.com>:

> Hi Yamin,
> 
> Checkout the -fleading-underscore / -fno-leading-underscore flag.
> 
> Note:  this is a powerful flag, since it has sweeping effects.
> 
> HTH,
> --Eljay
> 
> 




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Re: gcc name mangling - resolved

[y2bismil]

Hi all,

I think I've found the most appropriate solution.  Define the functions within
an extern "C" and using the asm 'naming' system.  

extern "C"
{
   extern void write_char(char) asm("write_char");
}


And if I can remember my old work correctly.  They had something like that,
which is why name mangling was not an issue.

Yamin

Quoting Eljay Love-Jensen <eljay@adobe.com>:

> Hi Yamin,
> 
> Checkout the -fleading-underscore / -fno-leading-underscore flag.
> 
> Note:  this is a powerful flag, since it has sweeping effects.
> 
> HTH,
> --Eljay
> 
> 




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