🚀 go-pugleaf

In article <1992Aug24.204813.16175@schunix.uucp> sonix@schunix.uucp (Duane Morin) writes:
>I'm trying to call an assembly routine from some standard Borland C++ (2.0)
>code.  Here's what I've got (in the C++):
>
>extern foo_bar3(int G, int P);
>.
>.
>.
>foo_bar3(i, x);
>
>And, in the ASM module, I've got:
>
>	PUBLIC	_foo_bar3
>PROC	foo_bar3	FAR
>	ARGS	G:word, P:word
>	.
>	.
>	.
>
>But C++ fails to recognize the foo_bar3 function.  Keeps telling me 
>unrecognized symbol.  As if it doesn't get the connection, because I'm not
>declaring the two int parameters in the actual definition in the ASM file.
>I got the syntax for doing this out of an "Interfacing C and ASM" book, so
>I assume that maybe I need to do somethng else to make this work in C++.

C++ uses name mangling.  Under C, the compiler pre-pends an underline
to the the function name, and writes it to the .obj file for the linker.
Under C++, the compiler also appends extra characters to the function
name.  This is name mangling.

These extra characters are based on the parameters of the function.
This is why you can overload functions in C++ (as long as the parameter
types differ), where as in C you must specify a unique function name.

As the Borland manuals state, the algorithm that Borland C++ uses
to mangle names is undocumented.  In other words, C++ compilers
use different techniques for mangling names.

>Any suggestions?  Minor errors in my transcription of the code might be 
>typos of mine just in this post, as I put that code in there from memory
>and may have slipped up (ARG vs ARGS or something).  Any help, however, 
>still appreciated.

Declare your assembler function with a C interface rather than a
C++ interface.  Change

   extern foo_bar3 (int, int);

to

   extern "C" {
      foo_bar3 (int, int);
   }

There are other ways to call assembler functions from C++.  These
other ways are documented in the Borland Manuals, such as chapter
5, "Interfacing Turbo Assembler with Borland C++".

>Thank you,
> Duane Morin
> Walker Sonix, Inc.
> sonix@schunix.uucp


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