C++ compiler question

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2 total messages Started by Hayward Lam Fri, 09 Oct 1992 00:38

#1355

Author: Hayward Lam
Date: Fri, 09 Oct 1992 00:38

19 lines
856 bytes

Hi there,

I'm pretty new in the NeXT world. This might be a stupid question
but I have to ask:
	I try to compile and link a c++ program. I type "cc++ program.c"
the linker returns the following:
	/bin/ld: Undefined symbols:
	_printf_FPCce
When I compile the with -c option, everything is fine. The object file
is created. But when I do a ld, it returns the same thing described above.
I'm not sure what's going on.

Help! 

Thanks in advance.

Regards,
Hayward
email to hlam@bnr.ca

Re: C++ compiler question

#1442

Author: Jim Large
Date: Mon, 12 Oct 1992 17:14

54 lines
2364 bytes

In article <1992Oct9.003819.3434@bmers95.bnr.ca> hlam@bmerh136.bnr.ca (Hayward  
Lam) writes:
> 	I try to compile and link a c++ program. I type "cc++ program.c"

First of all, if you name your program "program.cc", then you can compile it  
with the command, "cc program.cc".  This will not fix your problem (which was)

> the linker returns the following:
> 	/bin/ld: Undefined symbols:
> 	_printf_FPCce

You are trying to call a C function (printf()) from a C++ module.  To do this,  
you must surround the declaration of printf() with 'extern "C" { }'.

Since all of the NeXT libraries were compiled as C, or Objective-C, you  
probably want to wrap the extern construct around all of your includes as  
shown:

extern "C"
{
#include <stdio.h>   /*contains declaration of printf()*/
#include <
    .
    .
    .>
}


Why?  Because C and C++ translate function names ==> symbol names differently.  


In C, names are translated by prefixing an underscore, so that 
	printf(const char *, ...)
becomes
        _printf


In C++, the translated names encode the argument types, and
	printf(const char *, ...)
becomes
        _printf_FPCce


This is what makes overloading possible.  If you declare
	printf(int, int);
C++ assumes that you are defining a DIFFERENT FUNCTION from the printf() that  
we all know and love.  Therefore it outputs a different symbol name, namely
	_printf_Fii

 
----------------+------------------+------------------------------------
     |\ /|      |  Jim Large       |  Visual Understanding Systems, Inc.
     | V |      |  jml@visus.com   |  2100 Wharton St.                  
   \_|   |__    |  (412)488-3600   |  Pittsburgh, PA  15203

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