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From: steve@taumet.com (Stephen Clamage)
Newsgroups: comp.lang.c++
Subject: Re: C/C++ link in TC++
Message-ID: <453@taumet.com>
Date: 13 Sep 90 15:44:43 GMT
References: <4800101@m.cs.uiuc.edu> <577@dptechno.UUCP>
Organization: Taumetric Corporation, San Diego
Lines: 46

cw@dptechno.UUCP (Charles Haden) writes:

>In article <4800101@m.cs.uiuc.edu> reed@m.cs.uiuc.edu writes:
   ...
>>I've attached a code sample below that fails when I do the following:
>>	tcc -c y.c
>>	tcc -c x.cpp y.obj

>Your main problem lies primarily in the command line invocations
>of the compiler. What I mean by that is your problem is not in
>your source code it is in the way you are using the compiler.
>As you should know from the manuals that you can compile both
>"C" and "C++" source code with the compiler. What you probably
>didn't read it that the compiler treats prototyping differently
>based on the file extension ( default setting ). When compilling
>a C++ source file, the function name is "tweaked" you might say
>internally to allow for function overloading. This tweaking is
>not normally done to standard C source code prototypes, since
>overloading of function names is not allowed. There is a switch
>however, that will force standard C source files to be tweaked
>when compiling.

This explanation is not really correct.

Turbo C++ is really two compilers in one:  it is a C compiler, and it is
also a C++ compiler.  In the absence of compiler flags, a file with an
extension of ".CPP" will be compiled by the C++ compiler, and one with
an extension of ".C" will be compiled by the C compiler.  The "-P" flag
forces ".C" files to be compiled by the C++ compiler.  (I don't mean
that there are necessarily two complete compilers hiding in one .EXE
file, but that the behavior is as if there were two compilers.)

C and C++ are different languages, and have some different rules.  One
C++ rule is that any function not declared
	extern "C" ...
is expected to be a C++ function, and follows all C++ naming rules and
calling conventions.  If a function is declared so as to make it appear
to be a C++ function, but is really a C function, the program can be
expected to fail in some way.  The most common way to fail (true for
all current C++ systems I know of) is that the program will not link.
The link failure is due to the different ways function names are
treated in C and C++.  The discussion in this paragraph is not
unique to Turbo C++, but applies to any C++ implementation.
-- 

Steve Clamage, TauMetric Corp, steve@taumet.com