Xref: utzoo comp.lang.c++:1931 comp.lang.fortran:1487
Path: utzoo!utgpu!attcan!uunet!husc6!bloom-beacon!tut.cis.ohio-state.edu!osu-cis!att!cbnews!mjs
From: mjs@cbnews.ATT.COM (martin.j.shannon)
Newsgroups: comp.lang.c++,comp.lang.fortran
Subject: Re: f77 and C++ w/ cin/cout: can it be done?
Summary: main must be compiled by cfront
Keywords: f77 C++ cin cout printf
Message-ID: <2056@cbnews.ATT.COM>
Date: 10 Nov 88 15:34:31 GMT
References: <1118@rivm05.UUCP>
Reply-To: mjs@cbnews.ATT.COM (martin.j.shannon)
Organization: AT&T Bell Laboratories
Lines: 65

In article <1118@rivm05.UUCP> ccea3@rivm05.UUCP (Adri Verhoef) writes:
>- I have this fortran-file "m.f":
>      program main
>      call hello()
>      end
>- and I have this C++-file "s.c":
>#include <stream.h>
>void hello_()
>{
>	STATEMENTS;
>}
>- The first time, I replace STATEMENTS by:
>	printf("Hello, %s\n", "world");
>$ a.out
>Hello, world

This works because there are no static constructors involved, so it doesn't
matter which compiler generates main.

>- The second time, I replace STATEMENTS by:
>	cout << "Hello, world\n";
>$ a.out
>Bus error - core dumped

Since the static constructor for cout was never invoked, there is no
initialiaztion performed for the stream, and the constents of the class are
garbage.

>- The third time, I replace STATEMENTS by:
>	char str[128];  cin >> str;
>$ a.out
>Memory fault - core dumped

Since the static constructor for cin was never invoked, there is no
initialiaztion performed for the stream, and the constents of the class are
garbage.

In general:
Cfront recognizes that main is the 1st executable statement in a source file,
and appropriately replaces the user's main with code that arranges to make sure
that static constructors are called.  Thus, when mixing languages (not a
particularly safe thing to do; though possible in many systems), the executable
code generated for main must come from cfront.

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-- 
Marty Shannon; AT&T Bell Labs; Liberty Corner, NJ
(Affiliation given for identification only.)